Diver Medic and Aquatic Safety Issue 5 Aug 2015

ISSUE 5

DIVER &nd AQUATIC SAFETYMEDIC

Moving in extreMe environMents

Carbon dioxide and diving

barraCuda Case study

By James e Clark

By Paul Haynes

By Dr anke FaBian

haveall the

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Warning: graphic images, reader discretion advised.

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ISSUE 6 OUT OCTOBER 2015

DIVER MEDIC & AQUATIC SAFETY

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Letter from the editor By Anna "Nudi" Burn

Skin cancer, a son of a beachBy Dr Suzanne Gaskell

Through my eyes By Butch Hendrick

Moving in extreme environments By James E Clark

Carbon dioxide and diving By Paul Haynes

Learning from experience By Gareth Lock

Quiz How Clued Up Are You on Technical Diving?

Does SCUBA diving have a retirement age? By Dan and Betty Orr

Barracuda case study By Dr Anke Fabian

Start or improve a public safety dive team? By Andrea Zaferes

Where have all the divers gone? Part 3 By Butch Hendrick

Unexpected air pockets By Brittany Trout

Editor-in-ChiEfChantelle Newman

Editor

Anna Burn

tEChniCal EditorSAndrea Zaferes, Gareth Lock

dESignErS

Allie Crawford, Sarah Crawford

MEdiCal and diving SpECialiSt ConSultantSDr Anke Fabian

Dr Adel Taher and Dr A SakrDr Suzanne Gaskell

diving ConSultantS

Dan and Betty OrrJill Heinerth

advErtiSing and SubSCriptionS

Chrissie Taylor Newman

ContributorS -thank you to thE following

ContributorS: Thank you to the following contributors

James Clark, Andrea Zaferes, Dr Suzanne Gaskell, Dan and Betty Orr,

Paul Hynes, Butch Hendrick, Dr Anke Fabian and Aquamed,

Brittany Trout and DAN Europe, WDHOF, Anna Burns, Gareth Lock, SUUNTO,

Jill Heinerth, Rod Hancock

photographErS Cover Image by Jill Heinerth

PADI Course Director Ron Carmichael Diving in the Blue Grotto in

Florida

Polly Dawson, Anna 'Nudi' Burn, littlesam (shutterstock), kaohanui,

Gareth Lock, Team LGS, Marko Marcello, Adam J, Sergii Votit, Betty Orr, Wraysbury Dive Team, itlada, Daniel Handl,

Rich Carey, Aquapix, Christina Vackova, A. Fabian, Goncharuk Maksim,

Radu Bercan, YanLev, Richard Whalley

MagazinE addrESS The Diver Medic Ltd Great West House, Great West Road,

Brentford, TW8 9DF

tElEphonE +44 020 8326 5685 EMail [email protected]

www.dmaasm.com

Contentsissue 05 | august 2015

5

You are here for many of the same reasons I was keen to get involved with the magazine: you see the value of learning about diving safety through the insight of experts and the sharing of our own experiences.

As an avid diver, there is nothing I like more than talking to other divers about the passion we share for our oceans. From my first exhilarating dive with a playful pod of wild dolphins, to making underwater images of colourful nudibranchs, diving is almost always a joyful pastime.

As a community, sharing the highs comes naturally, but we tend to avoid the more uncomfortable moments, missing out on the valuable opportunities they offer to learn from each other.

At the very least, we have all experienced a split second of panic – a heart-stopping brush with the dangers of diving. Most of these moments go unreported, like the time I was diving Brighton's West Pier and changing conditions caused an exhausting long swim back to shore.

BSAC's official register, the Diving Incident Report, recorded 216 UK diving incidents in 2014. These incidents range from DCIs to missing divers, with sixteen lives lost in the course of one year. What is apparent is that many of the cases reported within this document could have been avoided were we better at adopting basic principles of safe diving practice. And, with the recent launch of the RNLI's latest #RespectTheWater campaign, aquatic safety is at the forefront of all our minds.

On a personal level, I feel strongly that these events are every bit as valuable to share as the joyful ones. They provide vital lessons for all of us and can greatly assist divers at every level in understanding some of the principle factors behind diving incidents.

The articles in this issue range from barracuda bites (page 52) to rebreather errors (page 32), with a great advice piece on diving into old age from Dan and Betty Orr (page 28). I hope you get as much out of reading the stories as I have from editing them.

Happy (and safe) bubbles!

A warm welcome to Issue 5 of Diver Medic & Aquatic Safety

issue 05 | august 2015

anna 'nudi' burnEditor

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Following your feedback from the survey we have decided to put a quiz together that has the option of easier or more challenging questions. We hope you will find something to challenge you, whatever level you’re at.

Answers to the questions will be put up on the Diver Safety and Aquatic Medicine Magazine website on 1st September 2015. Click this link for the answers http://www.dmaasm.com/survey-quiz/4589638662.

QuizThe Diver Medic & First Responder Challenge

a. lack of oxygen in the blood

b. hypoxia

c. Exercising at a high level burning up the oxygen in the muscles

d. Elevated ph of the blood due to excessive Co2

1 what triggers the response for breathing?

a. 1500 litres b. 1800 litres c. 1200 litres d. 1400 litres

3 how much gas, in litres, would you need for a square profile dive to 25m for 20mins at depth using a single Aluminium 80 filled with 32% nitrox and a breathing rate of 17 litres per minute on the surface? assume 10m/min descent and a normal ascent profile with a three minute stop at six metres. Choose the volume closest to your calculations.

a. bwraf

b. guE EdgE

c. bar

d. it doesn’t matter, as long as you do one on every dive and it covers the essentials to provide a working gas supply for the dive, your equipment works, you know what the plan is and you know when the dive will end.

2 which is the most important check you can do prior to jumping the water?

diver MediC & aQuatiC saFety

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6 using the same dive parameters as above, what about if you extended your bottom time on the dive to 35mins? Could you still do the dive with your buddy?

5 Explain why?

a. yes

b. no

4 you are now diving with a buddy who will be with you for the whole dive. do you have enough gas in your aluminium 80 to do the dive?

3

5

4

6a diving colleague comes to you and says that they suffer from Multiple Sclerosis and have clearance to dive from a diving doctor, what considerations should you take into account post dive?

what does current limiting mean when describing o2 cells in rebreathers and what are the implications for the diver if a cell is current limited?

if a dive was being planned to 85m using trimix, what consideration needs to be taken into account with regards to the relationship between fo2 and po2 for the breathing (not necessarily decompression) mixes when getting in the water?

what is the most prevalent trigger for diving fatalities as determined by dan?

2 what is the relationship between pfo and dCS?

7 you have a slight cold that clears easily after taking some over-the-counter Sudafed. you are diving single cylinder tanks to 25m using nitrox, is the Sudafed going to be a problem?


1 what is a patent foramen ovale (pfo) and why can its presence impact divers?

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This is the first of a two-part article which explores inert gas narcosis, the effect on divers’ movement and function underwater and the proposed physiological mechanisms. Also discussed are some of the factors that affect the susceptibility of divers to the condition. Understanding the cause of this potentially debilitating problem is important to ensure safe diving practices continue. References for the article will be available at the end of the second article in next month’s Diving Safety and Aquatic Medicine Magazine or from this link as a standalone document – (create reference list).Background

According to some reports, recreational diving using self-contained underwater breathing apparatus (SCUBA) is an increasingly popular sport throughout the world. It is estimated that there are over 7 million qualified SCUBA divers, with up to 500,000 new divers being certified every year worldwide [1,2]. How many of these newly qualified divers continue to dive is hard to determine since no single authority is able to publish figures. In addition to those enjoying diving as a hobby, there is a body of professionals exposed to similar environments (oil and gas industry, rescue, scientific & archaeology, engineers, and diving chamber workers),

MOVING IN EXTREME ENVIRONMENTS:inert gas narcosis and underwater activitiesBy James E. Clark

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This article is reproduced here with kind permission. It is under copyright and the academic style of writing represents its original copyrighted format although we have adapted the layout for this publication. Source: Tipton and Bradford: Moving in extreme environments: open water swimming in cold and warm water. Extreme Physiology & Medicine 2014, 3:12.

DOI: 10.1186/2046-7648-3-12

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which the Bureau of Labor Statistics (USA) estimates to be around 3,600 in America [3]. Diving includes a number of factors that can affect function and movement, or endanger divers’ health. SCUBA diving is, however, a very safe sport and there are, on average, less than 20 deaths per 100,000 divers (0.02%) annually according to the Divers Alert Network (DAN), meaning diving has a similar risk to most other forms of regular exercise [4, 5]. Individuals are exposed to water temperatures that can result in progressive heat loss [6], bulky thermal protection can impede physical

activity and there is a risk of entrapment or entanglement due to the bulky equipment carried [7]. Part of the risk involved in diving is the increase in ambient pressure when the body enters the underwater environment. For every 10 metres of sea water (msw) depth there is a net increase of 1 atmosphere (atm) of ambient pressure, such that at 10 msw the body is exposed to 2 atm, and at 30 msw 4 atm. Using SCUBA equipment, the diver receives compressed gas (usually air) at ambient pressure through a mouth-piece. Therefore, as a diver descends they are exposed to increased inspired gas pressures, the consequences of which are not trivial. Understanding the consequences of hyperbaric exposure requires the application and knowledge of complex physiological processes more than other environments in which humans move [8]. The hyperbaric environment carries the risks of barotrauma, decompression sickness and equipment failure resulting in suffocation or drowning, the results of which can be life-changing [9]. The physiological effect of hyperbaric gases on SCUBA divers can loosely be divided into: those resulting from prolonged exposure such as decompression illness (DCI) and the immediate, acute, effects such as oxygen toxicity; and the narcotic effects of inert gases which is the focus of this review [2, 9-11].

One of the first reports of what is now known as inert gas narcosis (IGN) was by Colladon, a French physician who, in 1826 descended to 20 msw in a diving bell. He described “…a state of excitement as if I had drunk some alcoholic liquor…” [12]. Over the subsequent century there were a number of reports of healthy divers becoming “mentally or emotionally abnormal” when diving to depth (~100 msw) and many of their symptoms were incorrectly attributed to impurities in the breathing mixture [2]. In 1935, Beknke and co-workers first suggested that nitrogen gas might have been the mediator of the observed behaviour, by utilising different gas breathing mixtures in their experiments [13]. Many have experienced the phenomenon of IGN but it still poorly understood and managed. Current guidelines on exposure to hyperbaric gasThe international diving agencies (such as the Professional Association of Diving Instructors, PADI, and the British Sub-Aqua Club, BSAC) try to mitigate the exposure to hyperbaric nitrogen by limiting the depths to which recreational divers can dive without additional training or equipment [14-16]. The Health & Safety Executive (HSE, UK) issue guidelines on the exposure limits for air diving operations, however these consider only depths and durations for decompression requirements and the US Navy Diving Manual discusses narcosis in the context of adequate training [17, 18]. With increasing depth there is increased risk. With an understanding about the onset of significant IGN in scuba diving, it is not at all surprising that most international sport diving qualifications have a depth limit of around 30 msw [14, 15].


narcosis and injury or death in diversThe Australian diving fatality database (Project Stickybeak) estimates that nitrogen narcosis contributed to ~9% of deaths reported. DAN cite 3.6% of reported deaths to have been caused by IGN in 2010 [2, 7]. Depth alone (without direct evidence for narcosis) was shown to have contributed to 54.3% of Advanced open-water training fatalities worldwide in 2010 [19].

Data from the British Sub-Aqua Club annual incident report database do not, however, demonstrate the association of increased depth with a greater likelihood of accident or injury (Figure 1). However, from the same data set is not possible to ascertain the actual number of deep (>30 msw) and shallow (<30 msw) dives undertaken in the same time period. Data from other training agencies however, indicate a bias in favour of shallow dives with around 70% of dives undertaken annually at depths of less than 30 msw [16]. Therefore, it is possible that, that the incidents in dives with depths >30 msw actually represent a greater proportion of the incidents reported. Uptake of inert gas at increased environmental pressureIn order to appreciate the consequence of breathing gases under pressure we must consider some gas laws. In the context of inert gas narcosis we must consider Dalton’s and Henry’s law. Dalton’s law of partial pressures states that in a mixture of gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases [20]. Therefore, air (20.9% O2, 79.1% N2) at 1 ata total pressure is made up of oxygen at a partial pressure (p) of 0.209 ata and nitrogen at 0.791 ata. At depth, when the ambient pressures increase so do the partial pressures of the constituent gases (e.g. at 20 msw the partial pressure of nitrogen

in air is 3 x 0.791 = 2.373 ata). Originally devised in 1803 by William Henry, Henry’s law states that at a constant temperature, the amount of gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid [20]. The consequence of these physical properties to the diver is that, when breathing gas under pressure, the constituents will dissolve in the body fluids (plasma, cytoplasm & lipids) proportional to the depth underwater since the alveolar/blood interface facilitates gaseous diffusion. Whilst the effects of high partial pressures of oxygen and other constituents of breathing gases should not be under-stated [11, 21], a consequence of exposing tissues, particularly neurological tissue, to high partial pressures of nitrogen is narcosis [12].

Signs and symptoms of inert gas narcosisWhile, for most, the onset of symptoms of narcosis is associated with deeper dives (see Table 1), some individuals might be susceptible at shallower depths [22]. At depths of less than 3 0 msw most symptoms are benign and, on the whole, hard to recognise (see Table 1) [12]. For instance, performance of un-rehearsed mental and physical tasks, such as sorting cards, is shown to be impaired as shallow as 10-20 msw [23]. Since symptoms tend to develop insidiously with depth, the onset of the more severe symptoms might render an individual incapable of self-control and at >30 msw the consequences could be catastrophic. Breathing compressed air at pressures exceeding 4 ata (30 msw), the equivalent of a pN2~3.5 ata, will invariably result in nitrogen narcosis [24, 25]. At depths greater than 30 msw, symptoms can resemble those of alcohol, marijuana and


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some benzodiazepine drugs [26, 27]. It is widely believed that the narcotic limit for diving on air is approximately 90 msw since studies to this depth have reported such severe symptoms of narcosis that individuals may find themselves completely incapacitated [28]. At these depths, when breathing air, the toxicity caused by the high partial pressure of oxygen would likely result in convulsions and drowning [21]. Manual dexterity and reaction times appears to be affected with increasing depth, but it is unclear whether this is a direct result of neuromuscular deficit, cognitive dysfunction or the

direct effect of pressure on the neurons [29, 30]. Differential actions of inert gases and pressure on neuronal function might explain some of the discrepancies between in vitro and in vivo studies, supported by observations of high-pressure neurological syndrome (HPNS)[24, 31]. HPNS is a manifestation of neurological symptoms when exposed to very high pressures (>100 msw). Indications include headaches and tremors, which are thought to be linked to enhanced release of the neurotransmitter serotonin since symptoms resemble those of serotonin syndrome, and is likely to have a distinct action to narcosis [24, 32, 33].


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Similarly, loss of balance control and the onset of vertigo have been observed at depth, often accompanied by tinnitus and hearing loss (neuro-vestibular). In the case studies reported it is not clear whether IGN was responsible for the functional change or whether this was secondary to barotrauma [34]. At depths of between 30 and 50 msw IGN affects central processing and it is believed that this is responsible for the amnesic effects of deep air diving [35-37]. Free-recall, recognition of performed and verbal tasks as well as input into long term memory are affected by even modest depths of 35 msw (the depth limit for most UK sport

divers) [35, 37-39]. Some studies also suggest that there are subtle, yet significant, changes to the arousal phase of the emotional response to stimuli when breathing pressurised air at narcotic depth [40]. In addition to cognitive function and coordination it is suggested that other senses may be altered. The perception of pain is reduced at even modest depths [41] but, interestingly, thermal sensation does not appear to be changed by narcosis. The perception of comfort, however, is altered at depth such that a diver might feel less uncomfortable in colder conditions, thus risking hypothermia [42, 43].

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Visual impairment has also been reported in some individuals [44-46]. Depth is usually associated with darkness and, in these circumstances, visual loss may be a compounding factor in incident manifestation when carrying out un-practiced tasks [47]. In addition to increased depth, risk factors that can affect an individual’s susceptibility to IGN include fatigue & exertion [28], cold, increased partial pressure of CO2, hypercapnia [48], intoxication [49] and anxiety [22]. To mitigate the effects of IGN, ascent to a shallower depth is the simplest management. This will reduce the pN2 in the blood and tissues and reduce the narcotic symptoms. There is some evidence to indicate, however, that some of the symptoms of IGN can persist even when removed completely from the hyperbaric environment [50, 51]. IGN can be prevented by avoiding diving to depths of >30 msw or by reducing the partial pressure of nitrogen in the breathing gas (by replacing some nitrogen with helium, which has no narcotic effect) [24, 52].

The precise role the symptoms of narcosis play in diver injury or death is not clear, as the data required for such analysis are not always available (maximum depth is not consistently recorded following an incident) [7, 16]. Over-confidence combined with confusion, neuromuscular incapacitation and cognitive decline are certainly contributing elements in diver injury or death at depth especially if current evidence as to the role of intoxication (by alcohol) in normobaric accidents is considered [27, 49, 53, 54].

However, there are almost always other factors that will influence the outcome of a diving accident, more so at depth [4]. What is evident from the available data, however, is that depths of greater than 30 msw are associated with a 3.5-fold increase in the number of incidents known to involve narcosis (Figure 2), and that dives undertaken at depths beyond 30 msw represent only 30% of all dives undertaken [16]. The incident records indicate that the common causal factors for diving-related injury are i) inadequate dive planning, ii) poor buddy checks, iii) failure to adequately monitor dive parameters during the dive, iv) diving beyond an individual’s personal capability, and v) lack of personal fitness, which is discussed elsewhere [4, 7, 16]. However, in the context of this review, there are a disproportionate number of reported incidents associated with deeper dives. SummaryAs we have seen, there is a credible risk of death if the effects of narcosis are not taken into account during both the planning and the execution phases of the dive. The signs and symptoms are not easily recognizable by the divers themselves when shallower than 30m, and indeed due to the euphoric effect in some divers when deeper than 30m, the seriousness of the effect is not appreciated. Manual dexterity and reaction times appear to be affected with increasing depth and this may mean that a failure is not detected in a timely manner, or if it recognized, there is an inability to resolve the situation. The next article will look at mechanisms of inert gas narcosis and identify physiological adaptations that have been identified in the research literature.


This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Clark: Moving in extreme environments: inert gas narcosis and underwater activities. Extreme Physiology & Medicine 2015, 4:1. DOI:10.1186/s13728-014-0020-7. © 2015 Clark; licensee BioMed Central http://www.extremephysiolmed.com/content/4/1/1


Table 1 Signs and symptoms of nitrogen narcosis at different depths [2, 78]

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Table 2 Relative narcotic strength of a number of gases [12, 22].

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so you want to start or improve a public safety dive team?

by andrea Zaferes

Part i – start with the right mentality


Stationed on a tri-anchored boat, the primary tender directs the primary diver while the backup tender profiles the search, documenting times, pressures, respiratory rates, distanced out, and live-time search locations,

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Drowning is the third most common cause of accidental death for adults and second for children in the USA. Every year new public safety diving (PSD) teams are formed to find drowning victims. These teams are formed by fire, law enforcement, EMS personnel and sometimes by people not already in the public safety community.

Water operations are unlike any other field in public safety. If a fire department wants to start a hazmat or high angle team do they go to the local hazmat shop or climbing store? If paramedic training is needed do we take a weekend American Red Cross class? Do police officers learn to shoot at the local skeet and trap club? Of course not. Yet most dive teams begin with training and equipment purchases at the local recreational dive store. Most PSD teams then continue to use sport procedures and equipment. Sport diving and public safety diving (PSD) have little to do with each other, and confusing them has resulted in far too many fatalalities.

Sport divers dive when and where they want, in good weather conditions, with plenty of planning. Their mission is to have fun. They do not have crying families, chiefs, and the media to contend with. Sport divers dive mid-water, in relatively clean, clear water. PSD divers are woken up at 0200 hrs in the rain, to rapidly pull a family out of a vehicle submerged in black, contaminated water. PSD divers dive on the bottom where entanglements are commonplace. PSD requires well-trained tenders, safety officers, backup divers and detailed documentation in case the scene is later determined to have been a crime scene or a lawsuit ensues.

PSD divers often move from an entry-level sport diving course to a sport rescue diver course that is designed to teach sport divers how to

save each other in high visibility mid-water. Sport rescue diver training does not address the needs of bottom dwelling, tethered, solo blackwater divers and certainly has nothing to do with conducting a PSD search operation.

For example, sport diving out-of-air procedures are irrelevant for solo-tethered-tender-directed divers. The latter should have quick-release pony bottles so if they need air they just switch to their pony and surface, unless of course they are entangled on the bottom, which is a situation requiring a specific set of well-trained procedures never addressed in sport rescue.

Sport divers use octopuses, which were created by Walt Hendrick, Sr. and Dave Woodward for shallow, high-visibility, mid-water diving. An octopus is merely a second mouthpiece coming off a single air source that can be passed off to an out-of-air buddy. What good is an octopus when a solo diver runs out of air? Having a second mouthpiece to an empty cylinder is pointless. And what happens when a backup diver passes an octopus off to an out-of-air primary diver entangled on the bottom? Now the backup cannot move around to help and is stuck to the primary diver. Octopuses have no place in public safety diving, yet sadly they are prevalent in PSD.

How many dive teams even have a contingency pony and full-size bottle on the scene set-up and ready to be brought to a low-on-air diver trapped on the bottom? It seems so logical, yet the answer is probably less than five percent of teams. Why is this true? Because the majority of PSD training is based on sport diving procedures, equipment, and mentality. Entanglement is the most common problem of bottom-dwelling divers. Today, while giving icetraining sessions to the Anchorage F.D dive team, the first diver experienced a tangle of fishing line

'The most important mission in starting or improving a team is to do what it takes to make sure team members can accomplish the one job they must do every time – go home.' Walt 'Butch' Hendrick.


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Practicing the blackwater contingency Hendrick Hand signals

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wrapped around his left heel up to his hip, which is a common occurrence where people fish. Do we train for this? Sport divers are sold expensive knives that they duly wear on their legs, yet, less than one percent ever receive hands-on training in entanglement management. PSD divers, who need this training the most, are not much better. We find less than 10 percent have hands-on entanglement management training.

The sport diver mentality says one knife worn on the leg with no training is sufficient, because you never really are going to need it anyway. PSD divers need the attitude that a cutting tool in trained hands can save your own or another diver’s life. Could a cutting tool be dropped in cold or blackwater? The obvious answer of yes should dictate that PSD divers wear at least two to three cutting tools. Sadly, the sport diver mentality prevails, and most PSD divers carry a single knife.

It gets worse. Divers who have worked on real or training entanglements learn that knives are inefficient for cutting such entanglements as fishing line, and can injure equipment or a diver when used in zero visibility. Paramedic shears are far more effective and safe. After having my BCD cut, my full face mask plate stabbed, and a regulator hose cut, by blacked out students during a few hundred the “save the entangled diver” drills, we made the rule of “no knives allowed to be used by the safety diver when aiding a primary diver.”

Yes, it gets worse. Besides carrying the wrong cutting tool, carrying too few cutting tools, and not training how to use them, divers typically wear them in the place farthest from their reach and on the part of their body that can become entangled as it kicks the fishing line up off the bottom – their legs. Leg knife placement is poor sport diving at best. In addition, a dropped weight belt can become caught on a leg knife, as one Pennsylvania instructor discovered when his student was found drowned on the bottom

because the student’s weight belt slipped off and caught on the leg knife during the night dive of an advanced course. Cutting tools should be worn in the golden triangle chest area where they can always be reached and are the least likely to be an entanglement problem.

Look at the typical PSD diver, who happens to look like the typical sport diver. A snorkel is worn, which serves to increase entanglement risks with the added benefits of dislodging the mask and introducing more contaminated water into the diver’s mouth should the snorkel be used. Why are snorkels worn in the first place – to save air when at the surface? If that is the case, then something is really wrong with the dive procedures.

Gauges are dangling free so that they can drag along the bottom, snagging weeds and fishing line, instead of being secured under the diver’s arm, through the BCD arm hole, Octopuses are also left dangling to become snagged, to scoop up mud so that they wont work when needed, and so that they will be far less reachable when needed. Would police officers allow the position of their weapons to continually change throughout the day? Why do divers allow their life support tools to dangle and continually be in different positions throughout a dive?

Consider the life saving, very basic skill of “regulator retrieval”. More than ninety percent of sport and PSD divers use the side-sweep method which only works most of the time. Getting a regulator back in one’s mouth while submerged should be important enough to be reflexively done with a procedure that works every time – namely the over-the-shoulder method, which also allows divers to turn their air on should they ever, unbelievably, enter the water with their air turned off. Our research has shown that if a diver fails at the side-sweep method then the most likely result is an uncontrolled bolt to the surface, not an attempt at the over-the-shoulder method.

'Cutting tools should be worn in the golden triangle chest area where they can always be reached and are the least likely to be an entanglement problem.'


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So why do divers use the side-sweep method? They were taught both and then were allowed to use the seemingly easier method every time after that. Why would anyone teach two different techniques for a skill that needs to be reflexive? And then why allow the technique that could fail to become the status quo? Even sport divers should not be taught any method other than the over-the-shoulder method. The recreational attitude of “nothing will go wrong, diving is fun,” coupled with a financial motivation to promote that attitude and to decrease training standards to increase profits, prevails in the sport diving industry. PSD teams that develop from sport diving are faced with the consequences of this sport problem that could result in injury or death.

But wait, you may say, our team was trained by a PSD instructor. Hmmm, is that really true? It may not be. A common pitfall is when a team has a recreationally certified scuba instructor (PADI, NAUI, SSI, YMCA, etc…) in the department who trains the dive team. The instructor, by nature of association, is called a “PSD instructor” even though the instructor may have little or no PSD training. Sometimes a group of such instructors form a “PSD” certification training agency and go out and teach other teams. Now these teams believe they are receiving PSD instruction and certification.

The key is to look at what is being taught. Are they using octopuses, tether-lines with hand-loops, diver-directed diving or multiple divers on a line in low/no visibility, a knife on the leg, dangling gauges, or snorkels? If yes, then put a check in the sport column. Are the search patterns exactly documented and repeatable? If not, add a check to the sport column. Do tenders document the divers’ breathing rates every five minutes and use that information with the divers’ personal surface air consumption (SAC) rates to know fairly accurately how much air a diver has at any point during the dive in blackwater? Or are they training

teams to bring divers up every fifteen minutes for pressure checks, which disrupts search patterns and increases the risk of diver problems? Are team members even taught how to calculate diver SAC rates?

Are team members given hands-on training with specific, tested and proven procedures on how to discover and manage diver entanglement, injury, and out-of-air procedures in blackwater? Or are safety divers taught a generic “go to the primary diver, figure out what the problem is, then manage it.” Are divers given a maximum blackwater search time of 20 or 25 minutes or are they allowed to search beyond the mind’s concentration peak for 30, 40 or more minutes? Are divers allowed to surface with less than 70 bar in their main cylinder?

Part of the reason recreational procedures are allowed to spread throughout PSD is that there are no real accepted PSD national standards in the USA. The National Fire Protection Agency document 1670 is very general and not all departments follow NFPA. NASAR put out a set of guidelines but, again, these are general and are not used by many departments. PSD dive teams are currently exempt from OSHA, although that may change. Various training companies have their own standards, but currently, most teams just make it up as they go.

The result is a complete lack of consistency. A team in County A may use effective solo-tethered-tender-directed procedures, with quick release pony bottles, harnesses, lines marked every five feet, hazmat tested drysuits, backup and 90%-ready divers, three non-knife cutting tools all in the golden triangle chest area, and full-face masks. County A tenders are certified and know how to read divers bubbles to know within 200 psi how much air their divers have at any point during the dive, they draw the diver’s exact movements

'The instructor, by nature of association, is called a 'PSD instructor' even though the instructor may have little or no PSD training.'

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on a profile map, and they have a specific five-factor system to accurately determine if an area can be secured or if it needs to be re-searched. Their SOP states that their maximum dive time is 25 minutes, maximum tether-line length is 38 metres, maximum depth is 18 metres, and if the current is greater than ½ knot then the dive cannot be done from shore.

In the next county over, Team B dives three divers on a line, with wetsuits, right-handed octopuses, knives on their legs, lines marked every ten feet with knots, no certified tenders, standard masks, and no specific and tested contingency procedures. They bring their divers up every fifteen minutes to check their air. They have no maximum dive time, they will dive to 40 metres, they do not measure the current, and have no specific way to decide if an area is secured or needs to be re-searched. Because of the lack of nationally approved and tested standards, Team B may look safe and effective until you see Team A.

The moral to this story is that if you want to start a PSD team, or improve the one you have, you need to begin by really thinking. You need to be very critical and question everything you hear and see. Is a procedure based on proven, tested, logic or is it something learned from Al, who learned it from Joe, who probably got it from Dan, who was a sport diver who started the team fifteen years ago?

Take the time to read, watch, and ask lots of questions. Your family will thank you. Safe diving always.

lifegaurd Systems www.teamlgs.compob 594 Shokan ny 12484 [email protected]

'You need to be very critical and question everything you hear and see. Is a procedure based on proven, tested, logic.'


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Skin cancer, a son of a beach


By Dr Suzanne Gaskell

Skin cancer, a son of a beach

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It is a sobering fact that the UK incidence of skin cancer has doubled in the last 20 years, with the disease showing a steady increase worldwide. The World Health Organisation estimates that one in three cancers diagnosed worldwide are of the skin, with an estimated one in five people developing it in their lifetime.

Divers are at particular risk since they tend to have high exposure to Ultraviolet (UV) light, often in climates that their skin is not suited to. Suncream can be expensive, requires frequent applications when diving, and can even be uncomfortable – many of us are familiar with the sting of suncream that has worked its way into our eyes during a dive. Some research shows that it damages the phytoplankton and some people find it damages wetsuits. It is understandable that people may not bother applying it, even if they feel they know the risks. Modern society has cemented the idea of a tan being a sign of beauty and good health – let me say now there is nothing healthy about a tan. It is essentially your skin’s way of showing it is trying to fight off further UV damage.

There are three types of UV radiation: A, B and C. UVC is fully absorbed by the atmosphere, but most UVA and 10% of UVB reaches the earths’ surface. These rays damage the genetic makeup in the skin causing mutations, which increase the risk of cancer. UV radiation is not without its useful properties. It activates vitamin D, which is essential for bone formation. It is also used in some medical settings to help treat skin conditions such as psoriasis, a scaly itchy skin condition. It is important to emphasise that this is done under tightly controlled conditions and does not reflect everyday exposure. Excessive UV exposure causes sunburn, premature ageing, skin cancer and unpleasant non-cancerous skin lesions. For the majority of us, the negative effects far outweigh the benefits. With a thinning ozone layer allowing more harmful rays into our environment, an increased incidence is to be expected, however the main contributing factor is our irresponsibility in the sun. Experts believe that if we are safe in the sun and learn how to recognise early signs of the disease, as many as four in five cases could be prevented.

With the UK incidence of skin cancer doubling in the last 20 years, Dr. Suzanne Gaskell explores what’s causing this growth.

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what is skin cancer? Cancer is an abnormal and uncontrolled division of cells. There are three main types of skin cancer: Malignant melanoma; squamous cell cancer and basal cell carcinoma. These manifest in different layers of the skin and all are attributed to UV exposure. Despite only 4% of skin cancers being melanomas, the disease accounts for 80% of all related deaths and is therefore the focus of this article.

Melanoma is cancer of the Melanocytes. These are cells in the lower layer of the skin that produce melanin. Melanin absorbs UV radiation to protect the skin from damage. It is worth noting that while black and fair skinned people have the same number of melanocytes, those with black skin produce more of the UV fighting melanin pigment. Skin cancer is 20 times more common in caucasians.The message is simple: skin cancer is increasing and we are responsible for this. Divers are at particular risk. Beauty is skin deep, so is skin cancer…..wear sun screen.

Skin Cancer fact Sheet

risk factors: UV exposure Preexisting molesFamily historySkin typePre-existing moles types of Melanoma: Superficial SpreadingThis accounts for 70% of Melanomas and is most commonly seen on the lower leg and back.

NodularMost commonly seen on the trunk. These pigmented lesions grow rapidly and may form ulcers (breakages in the surface of the skin).

Lentigo MalignaThese usually arise around hair follicles on sun damaged skin, especially the face. It can occur many years after the damage has occurred, which is reflected in the fact that this type of cancer is most commonly diagnosed in people over 60.

Acral LentiginousThis type accounts for the majority of melanoma in black skinned populations. It affects unlikely places such as under the nail and palms of the hands and feet. For this reason, it is usually detected at a late stage and has a poor prognosis.

treatmentMelanoma is an aggressive disease and surgery remains the most effective treatment option. The prognosis depends greatly on how early the cancer is detected, which is why it is so important to be sun safe and monitor any moles. 5 year survival tails off rapidly for every mm increase in invasion. If the cancer is <1mm deep when diagnosed, you have a 95-100% cure rate. Whereas if it is >4mm deep, that figure falls to 50%.

diver MediC & aQuatiC saFetydiver MediC & aQuatiC saFety

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tips to prevent Melanoma:

Do not burnCover up with loose clothingSeek shade during the hottest part of the dayApply suncream with a minimum SPF of 15

how to detect Melanoma:

Apply the ABCDE approach to skin lesions. If you see a change in any of the following then visit your doctor: asymmetry border irregularity Colour variation diameter over 6 mm Evolving (changing shape or size)

references:

www.who.int/uv/health/en/


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http://www.who.int/uv/health/en/


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Does SCUBA diving have a retirement age?

by Dan and Betty Orr

“You can’t help getting older, but you don’t have to get old.”– George Burns

If you were born between 1946 and 1964 you are lucky. That makes you part of the Silver Tsunami known as the “Baby Boomers” and one of 78 million Americans or 1.6 billion worldwide. Not all ageing Boomers are divers, or even wish to be divers (their personal loss), but all wish to stay as healthy and active as possible. Research shows that longevity is primarily a result of lifestyle (70% of effects). In general, Baby Boomers are living longer, having lower rates of disability and achieving higher levels of education. Baby Boomers are known to work hard, play hard and spend hard (Ziegler, 2002). Ageing is a fact of life, but how we handle it can make the difference between enjoying diving long into our golden years or having to hang up our fins prematurely.

When we take stock of our physical abilities as we age, there are absolutes that we should be familiar with. The most basic is that many of our organs and bodily systems lose function at approximately 1% per year beginning around age 30, but the majority of these changes are not truly apparent until approaching the age of 70. The good news is that with age usually comes wisdom and that improved judgment and reasoning can help us compensate for most negative changes. Knowing that we will have some level of disability as we age brings us to how we can make accommodations and still dive safely. One way would be to adopt a philosophy similar to the U.S. Marine Corps mantra: improvise, adapt and overcome.

There are six basic characteristics of ageing that we, with a little planning and foresight, can prepare appropriate countermeasures for.

1: loSS of balanCEAgeing may cause some loss of balance, spatial orientation and coordination. Many of our body systems are involved with our sense of balance and space, including vision, inner ear, muscles and joints. All interact in a delicate ballet to keep us upright and oriented. As our eyesight changes, inner ear cells die off and muscle and joint strength declines, these combine to throw off the signals to our brains regarding balance.

Sometimes the simplest solution is the best way to counteract these effects.

Ask for help when donning or doffing gear and consider removing your gear while in the water before re-boarding a dive boat. When selecting your dive destinations, take into consideration how the dive boat platform is structured, ask if it has a pull up bar to ease exiting the water and inquire if the ladder is foot-friendly. Most importantly: move at your own pace. Let your buddies and the divemaster know that you are choosing to be cautious and methodical so that you may enjoy diving for many years to come.

2: CognitivE iMpairMEntOur nervous and sensory systems decline with age but it does not necessarily have to define or limit our diving. Life experiences can help us develop workarounds for some of the challenges presented by ageing.

Although every dive should begin with a discussion or briefing of the dive plan and expected scenarios, it is even more important that older divers feel free to ask questions and ask for clarification.


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Use either old school slates or any of the new technology available to write down the plan so that you can easily access and review the plan if need be. Become more situationally aware of anything that could impact your safety (depth, time, air-consumption, currents, water temperature) and discuss how you might compensate for these forces with your buddy.

3: loSS of StrEngth and StaMinaMany systems combine to provide us with the agility, strength and stamina that may have allowed us to push through difficult diving conditions in the past. Loss of muscle mass and flexibility, bone demineralisation and loss in range of joint motion, decreasing heart rate and smaller ventilator capacity all come into play with each year that passes.

This is truly where lifestyle choices of diet and exercise, both aerobic and resistance styles, may have the greatest ability to slow the marching of time.

Be mindful of your true levels of fitness, not relying on what your memory tells you what you used to do. Be aware that you may become fatigued faster, that you may recover more slowly from a strenuous dive, that your range of motion may be reduced and your breathing may be a little more laboured. Slow down, ask for help and dive smarter not harder. The number of years since certification does not always equate to the same number of years of experience. Dive to your true abilities and experience, not just what your card says.

4: viSual iMpairMEntEyesight changes, such as clarity, depth of field, peripheral vision, and colour perception (especially the colour blue) all impact how we see the world around us as we age. As us divers age, we may reach a point where our arms or hoses are no longer long enough for us to clearly read our gauges both underwater and on the surface. If anyone, regardless of age, has difficulty reading their gauges, it’s imperative they consider a different style or purchase a mask with prescription lenses.

5: hEaring iMpairMEntAs the old joke goes: you can always tell when you are in a roomful of divers because everyone is speaking loudly and asking, “What did you say?” The natural ageing process will cause a loss of hearing acuity at the higher end of the spectrum. Couple that with the loud noises that are generally found at dive sites and aboard dive boats and it may become difficult to hear pre-dive briefing clearly. Ask those around you to speak loudly and distinctly, ask questions if in doubt, write the plans down and confirm that you are on the same page as your buddy and divemaster.

6: inCrEaSEd SEnSitivity to Cold and SunlightAgeing causes a lowered metabolic rate which, along with a decrease in blood flow to tissues, can make us more sensitive to cold. Changes to our skin decrease our tolerances of injuries, increases injury recovery time and makes us more susceptible to sunburn. On top of this, sweat glands shrink, making us more prone to heat-related injuries. Cumulatively, these changes may increase the likelihood of dehydration, which can significantly increase the risk of decompression sickness.

Compensation for these changes is fairly straightforward. Make sure you have adequate exposure protection, even in warm water; apply ample sunscreen 30 minutes before exposure and then reapply frequently. Keep yourself properly hydrated with non-caffeinated and non-alcoholic drinks one to two hours before any vigorous outdoor activity then again post-dive. All these steps will go a long way to mitigate those negative effects. Of course, adequate hydration may require more frequent urination, leaving you with a choice of voiding into your wetsuit or using a nearby head on the boat, but it is not a wise decision to limit fluid intake to reduce your lavatory needs!

Enjoyment is the purpose and the reward of every diving experience, regardless of age. Divers of any age could benefit by following some of the suggestions mentioned here. Choosing conservative dive options, avoiding strong currents or wave actions and using enriched air nitrox blends as though they were air are all ways to add to the general safety of your dives. Practice using slow ascents, be situationally aware and carry surface signalling equipment to enhance your surface visibility and provide additional buoyancy. Remember to take breaks. Do not feel compelled to make every dive and instead appreciate the dives you do make more fully.

Finally, to answer the original question, “Does scuba diving have a retirement age?” There will come a day that you may have to make the decision to hang up your fins. This decision should come when the sport is no longer fun or if you believe you may be putting yourself, your buddy and others in the water at risk.

You must have realistic confidence in your skills and ability to be a safe diver. It is a difficult decision and one that only you can make, with the guidance of a knowledgeable physician who is familiar with diving medicine, your life priorities and safety resources offered by organisations such as Divers Alert Network (DAN). You can delay that decision with proper nutrition, regular exercise and other healthy life choices.

Diving is an important part of our lives and with proper preparation, methodical execution and a positive mindset, it is one in which we can all safely participate and introduce to the next generations of future divers.


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"You must have realistic confidence in your skills and ability to be a safe diver"

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"When respiratory physiologists speak of respiration they are not referring to breathing, instead they refer to the generation of energy within the body’s cells"


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introduCtionHypercapnia, commonly referred to by divers as carbon dioxide (CO2) poisoning, represents a severe hazard for all divers regardless of whether you are using Open Circuit (OC) Self-Contained Underwater Breathing Apparatus (SCUBA) or re-circulating SCUBA (rebreathers). The impact of a hypercapnic event can be life-threatening, yet of all the gas-related illnesses we may potentially encounter, hypercapnia is the least discussed during diver training. As a result, amongst the general diving population there is a limited understanding of the mechanisms that result in hypercapnia. Of all the diving related gas illnesses I have unfortunately experienced over my 25 year diving career, due to its insidious nature, it is hypercapnia I have come to fear the most.

Please then stay with me as I try to drag this diving malady out of the closet and into the spotlight.

baSiC rESpiratory phySiologyFor every 22.5 litres of free surface gas we pass in and out of our lungs, we extract and metabolise approximately one litre of oxygen (O2). As ventilation increases, the amount of gas passed in and out of our lungs also increases, along with the amount of oxygen extracted from that gas. For example: if our Respiratory Minute Volume (RMV) is 20 litres per minute, which in diving terms equates to the term Surface Air Consumption (SAC), we would

metabolise approximately 0.89 litres of oxygen during that minute (i.e. 20 RMV ÷ 22.5). If our ventilation increased to 40RMV, we would extract and metabolise approximately 1.78 litres of oxygen from that gas over a period of one minute.

When respiratory physiologists speak of respiration they are not referring to breathing (ventilation), instead they refer to the generation of energy within the body’s cells. CO2 is the waste product of respiration, the cellular ‘combustion’ process where oxygen and fuel (food) is converted to the energy necessary for the body to do work, repair and sustain itself. In general, for every 1.0 litre of oxygen consumed, we produce approximately 0.9 litre of CO2. This ratio is termed the respiratory quotient or respiratory co-efficient (RQ). RQ can vary dependent upon the ‘fuel’ being ‘burnt’, increasing with a higher carbohydrate diet and decreasing with a higher fat based diet. Therefore it can be seen that as oxygen consumption (VO2) increases, CO2 production (VCO2) increases in accordance with the RQ. An important point to remember here is that oxygen metabolism, i.e. the amount of oxygen molecules consumed during the generation of energy needed to produce a given amount of work, is independent on depth. Therefore a given amount of work requires the same amount of oxygen molecules necessary for energy generation whether that work is conducted at the surface or at depth.

Carbon dioxide and diving:It Is tIme to come out of the closet

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As a consequence both the amount of oxygen extracted from a given amount of ventilated breathing gas and the RQ is independent of depth. In accordance with the ratios discussed above, as a generalised working example, a ventilation rate of 30 RMV will result in a VO2 of 1.33 litres (RMV 30 ÷ 22.5) and VCO2 of 1.20 litres (VO2 1.33 x 0.9 RQ).

Blood circulation (perfusion) via the heart transports oxygen from the lungs to the body’s tissues, while CO2, the resulting waste product, is transported away from the cells to the lungs to be eliminated from the body during exhalation. The transportation of CO2 within the blood is achieved by three mechanisms:

1: Dissolving in blood plasma.2: Loosely binding with haemoglobin and proteins in the blood.3: Chemical transformation to form bicarbonate, a process that is re-versed when blood enters the capillaries of the alveoli.

To stimulate breathing, a certain level of CO2 is maintained within the blood. Above this level, so long as the production of CO2 is balanced by its elimination, CO2 levels will remain within normal parameters with no undue physiological effect. During exercise, as more oxygen is consumed, the resulting increase in CO2 in the blood triggers receptors in the brain stem to increase ventilation. As a consequence, our RMV increases through a combination of increasing tidal volume (the size of each breath) and increasing the frequency of breathing (the amount of breaths per minute). Thus under normal conditions, when exercising, the balance between CO2 production and elimination is again maintained. This process is captured by the simple equation: PaCO2 = VCO2 ÷ VA

Where:PaCO2 = arterial blood CO2 partial pressureVCO2 = CO2 production by the body’s tissuesVA = alveolar ventilation

The above equation demonstrates that arterial CO2 levels will increase if there is a reduction in alveolar ventilation. It is this direct association between the elimination of CO2 through ventilation and the level of CO2 in the body that is critically important to

understanding the problem of hypercapnia. Anything that restricts or limits our ability to ventilate can have a profound impact on CO2 elimination.

The ventilation limitations we may encounter when diving are discussed next. Effect of immersionAs soon as we immerse ourselves in a liquid a number of important physiological effects are encountered, which in some cases are adversely amplified by the type of SCUBA we are using. These changes include:

1: blood voluME rEdiStributionBlood that is normally pooled in the lower body and legs by the effect of gravity is shifted to the central part of the body under the combined effects of hydrostatic pressure and peripheral vasoconstriction. This increase in central blood volume and blood pressure effectively stiffens the lung. Although the effect is relatively small, there is now an increase in the breathing effort needed to overcome this lung ‘stiffening’. The centralisation of blood is interpreted by the body as excess fluid and triggers the need to urinate soon after entering the water as the body tries to eliminate what it perceives to be excess fluid, a physiological phenomena known as immersion diuresis.

Note: it is the reverse of this hydrostatic pressure effect that can result in fatal hypovolemic shock and cardiac arrest if individuals who have been im-mersed at the surface for a long period of time, are pulled vertically out of the water. To avoid hypovolemic shock, recover a long term immersion casualty from the water in a horizontal position to enable the gradual redistribution of blood to the lower body.

2: StatiC lung load (hydroStatiC iMbalanCE)As we all know: water is heavy, with a weight of approximately 1kg per cubic litre. Due to the density of water, its mass is therefore able to exert considerable pressure over a small vertical distance. With all underwater breathing apparatus, to a greater or lesser degree, this results in the phenomenon known as Static Lung Load (SLL) or hydrostatic imbalance (figure 1a).

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Consider an immersed diver in a vertical head up orientation using open cir-cuit SCUBA (figure 1b). The second stage demand valve is positioned approximately 20 centimetres above the centre of the lungs (lung centroid). Remember that 10m (1000 centimetres) of water depth equates to approximately one bar (1000 mbar) of pressure. Therefore this 20 centimetres of vertical distance in the water column equates to approximately 20 mbar of pressure. The purpose of a demand valve is to reduce intermediate pressure from the first stage high-pressure reducer to ambient pressure at the mouth. However the centre of the lung, the location where gas from the demand valve is ultimately destined for, is approximately 20 mbar lower in the water column and thus subject to 20 mbar of increased hydrostatic pressure compared to the mouth. On inhalation the diver therefore has to overcome this 20mbar of hydrostatic pressure imbalance to draw gas from the demand valve down the water column into the lungs. This is termed a negative SLL and the diver may sense resistance to inhalation.

Note: there is a suggestion that large negative hydrostatic pressure imbalances associated with certain designs of back mounted rebreather counterlungs could be a mechanism for pulmonary oedema (fluid accumulation within lung air spaces), where blood fluid (plasma) is pushed or drawn through the alveoli gas/blood barrier (figure 1c).

Figure 1

In contrast, now consider an open circuit diver in a head down orientation. In this example the demand valve is positioned approximately 25 centimetres lower in the water column compared to the lung centroid. As a consequence, the mouth is subject to approximately 25 mbar of increased pressure compared to the diver’s lung centroid. The diver has to overcome this pressure by the expenditure of additional energy to push exhaled gas down the water column, out of the mouth and past the exhaust valve. This is termed a positive SLL and the diver will sense resistance to exhalation but assistance on inhalation as gas rises to the highest point under hydrostatic pressure. This is also a reason why a demand valve can go into free-flow when the diver is in a head down position (figure 1d).

Note: there is evidence to suggest that a positive SLL is physiologically preferential to a negative SLL; in other words we find it easier to blow out as opposed to breathe in.

It is the effect of SLL that is one of the physiological reasons restricting the practical length of a snorkel to approximately 35 centimetres; the other reason is excessive dead space resulting in the re-inhalation of exhaled CO2. However, with regards to SLL: if a snorkel had a length of one metre (100 centimetres), when submerged there would exist an approximate pressure difference between the mouth and the surface of 100

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R. E. Moon, A. D. Cherry, B. W. Stolp, E. M. Camporesi, Journal of Applied Physiology Published 1 February 2009 Vol. 106 no. 2, 668-677 DOI: 10.1152/japplphysiol.91104.2008

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mbar. Putting aside the problem of re-inhaling CO2, this pressure differential would require considerable energy expenditure to overcome the hydrostatic imbalance, making inhalation extremely difficult and likely unsustainable. There is a recorded case where the use of a 2m snorkel was attempted, representing a massive SLL in human physiology terms (200 mbar positive SLL). The result was cardiac failure as the flexible major blood vessels that are in direct contact with the lung (and thus atmospheric pressure) distended (expanded) sufficiently under hydrostatic pressure to overload the heart.

3: gaS dEnSityGas density increases linearly with depth; if you double the absolute pressure a diver is exposed to, the density of the gas being breathed will double. The human respiratory system has evolved to breath gas at around sea level where the viscosity (thickness) of air is relatively thin. However with increasing pressure, gas viscosity increases requiring greater energy to move that gas from one location to another (discussed later). When diving, breathing itself becomes an increasing aspect of the exercise workload. Because increasing gas density increases the resistance to gas flow, resistance, which has to be overcome by respiratory muscles (diaphragm and intercostal), respiratory failure through muscle exhaustion can quickly result during exercise.

As a clear and very alarming indication of the reduction in ventilation with depth, if we consider breathing air for the time being, manned hyperbaric pressure chamber trials have demonstrated that as a direct consequence of gas density, the amount of gas (air) that can be passed in an out of the lungs is reduced by 50% by the time a diver is at 30 metres and further reduced to around 40% at a depth of approximately 40 metres(Figure 2). As demonstrated by these trials, our ability to ventilate and remove CO2 during exhalation is reduced significantly with depth due to the effect of increased gas density. However, as previously discussed, our ability to metabolise oxygen and produce CO2 is independent of depth.

In other words: while we are quite capable of producing CO2 at depth, under certain conditions we are quite incapable of effectively eliminating CO2 at depth. In addition, SCUBA harnesses and exposure suits can restrict chest expansion. This can further add to respiratory muscle workload, increasing the potential of respiratory muscle exhaustion.

Note: it is the effect of increased gas density and subsequent reduction in ventilation that results in the well-recorded phenomena of ‘deep water blackout,’ where insufficient elimination of CO2 results in spontaneous loss of consciousness.

Figure 2.

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4: rESiStivE EffortIt must be remembered that gas is drawn into the lungs solely by action of the diaphragm and intercostal muscles, and exhausted from the lungs by the relaxation of those muscles and elastic recoil of the chest wall. There is no mechanical assistance to breathing when using SCUBA. All the necessary energy needed to do the work of ventilation is generated by a respiratory system that has evolved to deal with normobaric environments (the approximate pressure and gas density at sea level). The energy required to move or circulate a given mass of gas will vary according to the following key factors: 1: Gas density.2: Gas flow restrictions. 3: Gas velocity.4: Static Lung Load (SLL)

Consider this in the context of rebreather diving: Resistance to gas flow due to density has already been discussed, now combine this with a poorly designed breathing loop that causes high flow resistance as a consequence of (for example) small bore breathing hoses, small diameter gas flow orifices, abrupt changes of gas flow direction. The diver’s ability to move gas around such a breathing loop is severely compromised if exercise rates increase. When exercising, we breathe faster, therefore the gas velocity increases. Any resistance to gas flow is compounded because four times the amount of energy is required to double an object’s speed – in our case that object is a mass of gas. The work required to move or circulate this gas is then added to by the effect of excessive SLL. Note: Although more often associated with rebreathers, resistive effort can also apply to open circuit SCUBA. For example, a poorly designed, maintained or adjusted second stage demand valve can greatly increase the inhalation effort required to initiate the flow of gas into the demand valve and the effort needed to blow exhaled gas passed the exhaust check-valve (mushroom valve). Because our respiratory muscles are ill-suited to dealing with such workloads, during elevated work rates an increase in gas density, gas velocity, SLL and resistive effort can rapidly result in respiratory

collapse and the subsequent inability to effectively eliminate CO2.

the physiological impact of hypercapniaNow that we better understand the critical factors that reduce ventilation when immersed in a liquid, let us now take a look at the effects of inadequate CO2 elimination.

Carbon dioxide is highly poisonous, hence the body’s need to eliminate any excess as efficiently as possible. The detrimental effect of CO2 increases with arterial CO2 partial pressure (PaCO2). Elevated PaCO2 occurs as a result of:1: re-inhaling CO2 (for example failed rebreather CO2 scrubber canister or excessive breathing of dead space)2: inadequate ventilation (CO2 retention)

Carbon dioxide is also highly narcotic – perhaps over 100 times more than nitrogen – and can quickly result in unconsciousness, with death by drowning being the likely outcome. Cognitive functions are quickly impeded during a hypercapnic event. The narcotic effect may also be accumulative and thus amplified where excessive nitrogen and CO2 partial pressures are present. Although not always experienced during a hypercapnic event, excessive breathing rates are common and, as previously discussed, can quickly lead to respiratory muscle exhaustion or the depletion of open circuit gas supplies.

Carbon dioxide is a vasodilator, meaning it causes blood vessels to relax and expand; this increases blood flow through them and can result in the delivery of additional nitrogen to the tissues, in particular the brain, thus compounding narcosis.

The additional delivery of nitrogen to body tissues may also be outside the parameters assumed by the decompression algorithm being used, thus in-creasing the theoretical risk of DCI. With increased brain perfusion, if breathing hyperoxic gases (open circuit nitrox or closed circuit rebreathers), there is an increase in the delivery of oxygen to the brain, theoretically increasing the risk of Central Nervous System (CNS) oxygen toxicity.

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what can be done to avoid hypercapnia?It should be clear by now that excessive CO2 can result in respiratory failure, rapid depletion of open circuit gas supplies and/or spontaneous loss of consciousness – all of which are life-threatening, whether individually or cumulatively. In addition, some individuals are so called CO2 retainers, either as a result of their own innate physiology or through environmental conditioning, and have a reduced sensitivity to CO2. Through the suppression of ventilation in response to rising PaCO2, such individuals may therefore be more susceptible to CO2 poisoning.

There are various measures that can be taken to reduce the probability of hypercapnia:

1. restrict the depth to which you dive airSome training agencies advocate 50m as the maximum air diving depth whilst others advocate 30m as the maximum air diving depth. There are some training agencies that offer deep air training beyond 50m by promoting the management of nitrogen narcosis. Whilst under the right conditions nitrogen narcosis could arguable be managed by appropriate training, the problem of gas density and CO2 retention at depth still presents a significant hazard, particularly if work-rate increases. Therefore avoid deep air dives.

2. use helium in the breathing gasBeing a much lighter gas than nitrogen, helium is effective in reducing gas density, thus promoting effective ventilation and the efficient elimination of CO2. Therefore the use of trimix (oxygen, helium, nitrogen) has the benefit of reducing gas density and the effort needed to breathe, and also reducing retained CO2 levels.

An additional benefit is that based upon lipid solubility theory: helium is ap-proximately 0.23 times less narcotic than nitrogen, thereby reducing inert gas narcosis. The recent increase in open circuit and rebreather normoxic and even hyperoxic trimix training (recreational trimix) has arisen in response to the need to reduce gas density and nitrogen narcosis experienced at recreational diving depths.

Note: because of the potential for retained CO2 the British Royal Navy uses a heliox (oxygen and helium) diluent gas when diving closed circuit rebreathers below 30m.

3. Correct breathing techniqueThe practice of ‘skip breathing’ to conserve open circuit gas supplies should be strongly discouraged. The conscious reducing of ventilation results in the retention of CO2 – in effect the diver is deliberately self-poisoning. If exercise and thus CO2 production rates increase, the severe debilitating effects of CO2 could be quickly encountered.

4. Minimise exercise The minimisation of work-rate should be one of our primary objectives when diving. Throughout all phases of the dive we should be striving to keep exercise levels as low as is practically possible and avoid getting ourselves into a position that results in high ventilation rates, particularly at depth (remember figure 2). For this reason the use of a Diver Propulsion Vehicle (DPV) is of particular benefit for deep technical divers, particularly where high tidal flows or currents might be encountered.

5. Self awarenessRe-educate yourself and learn to recognise the signs and symptoms of CO2 poisoning:• increased breathing and heart rate• feeling an inability to inhale enough gas (dyspnea)• fear or terror• narrowing of peripheral vision• inability to perform simple tasks• nausea• physical weakness and loss of dexterity• headache

However, remember that spontaneous loss of consciousness can happen rapidly and unexpectedly with hypercapnia. Therefore if you are in a position where you suspect that you are experiencing a hypercapnic event, act early before the debilitating effects of CO2 take effect. Always remember that if something feels wrong then it is highly likely that something is wrong. Immediately reduce your exercise levels, take control of your ventilation and breathe deeply to flush out excessive CO2. Then get out of depth as quickly and safely as is practically possible.

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Assuming your production of CO2 begins to reduce and/or levels of inhaled CO2 do not increase, PaCO2 levels will begin to reduce as you ascend. However, the effects of hypercapnia can be long-lasting so do not expect an immediate positive effect from a reduction in depth alone. Reducing your depth also reduces gas density, thus promoting more efficient ventilation and CO2 elimination, extending your open circuit gas supplies.

In summary, during a hypercapnic event: • reduce your workload• take back control of your breathing• start your ascent at the earliest opportunity

If you are a rebreather diver, the probability of encountering hypercapnia is greatly increased. Therefore as soon as you have

any suspicion of a CO2 is-sue, switch to your open circuit bailout gas and commence an ascent at the earliest opportunity.

Having now looked more closely into the problem, it is hopefully apparent that safe diving requires a greater awareness of the issues surrounding hy-percapnia and the management of the risk it presents. Risk is a function of the effects of a hazard (something that can cause harm) combined with the probability of encountering that effect. Like all gas-related diving maladies, it is about management of the risk. This starts with understanding the hazard of CO2 and effects of that hazard. Through education and good diving practice, we can then reduce the probability of exposing ourselves to the effects of this hazard, thereby reducing and managing risk.

about thE author:Paul Haynes is a mixed gas closed circuit rebreather instructor trainer and deep shipwreck explorer with a 25 year military, occupational and technical diving background. Following early retirement from the British armed forces, for 10 years Paul managed the defence business for Divex Ltd, the world’s largest manufacturer of professional diving equipment. While at Divex, Paul was an integral member of its rebreather design and test team, helping de-velop some of the world’s most advanced military rebreathers and underwater life support equipment. As a founding member of Life Support Investigations Inc, a nonprofit organisation established to support US coastguard and law enforcement rebreather accident investigations, Paul has been involved in the analysis of numerous rebreather fatalities, both civilian and military. Besides technical diving instruction, Paul manages his own specialised defence diving consultancy business, training special operations forces, naval mine clearance diving teams and law enforcement agencies in the safe use of various rebreather technologies and underwater equipment.

www.haynesmarine.comfacebook: haynes Marine ltd

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Where have all the divers gone?

By Walt 'Butch' HendrickPart 3Learning how to dive is a bit like playing with Lego®: it is a process of building blocks, with each block working to support the next. It takes time to learn how to connect the pieces. As we continue to remove windows of time from basic diving courses, we can’t help but reduce many of the building blocks and therefore the chances of strong reflexive skill processing. You can’t remove 12 or more hours from any kind

of training curriculum without losing something at both the instructor and student level.

One of these important building blocks is what we referred to as a “ditch and don” (not to be confused with a NAUI bailout, which was an instructor skill). In speaking with more than a dozen new instructors teaching for thtree to five years with no less than a half a dozen instructor specialties (of which they are no longer required to receive advanced training before being sanctioned to teach) we are discovering that the ditch and don is now considered an unnecessary use of confined water time and is seldom taught at any level of the new diving curriculum.

We have removed one of the most positive confined water skills, where students would come up from a ditch and don exercise so excited and positive about their abilities to combine skills and perform what only a few evenings earlier they believed would be the impossible. This was the summation of a series of individual skills taught as building blocks, each supporting the next skill taught in a process of making the new diver confident, comfortable and eventually reflexive. It was key in building stronger equipment and overall water skills.

The ditch and don was not just there for the students, so they would understand how much they had accomplished in their personal water ability and build a positive energy to push them towards the next level of learning. It was also there for the instructor and their assistants, as they knew that each and every student needed to be comfortable and confident with every skill. We knew that it was our absolute responsibility to prepare each student to be ready for the ditch and don. It was a totally positive conclusion to multiple evenings and skills that brought the student to a level of excitement and energy that drives them to say, “Teach me more, make me as capable and ready as possible for a lifetime of continued diving.”

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Weekend dive classes cannot teach you everything you need to know to be a safe, confident, independent diver, let alone show you how to make diving more fun. Simple tricks like how to have a buddy help you don snug gloves can make the difference between entering the water in a relaxed, ready to have a good time state and getting in the water in a stressed, task-loaded mindset.

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Let’s take a look at many of the pieces that the ditch and don brought together.

The first night of confined water training is when most new divers have their first experience of putting their kit together. Simply learning how the tank, tank valve, first stage of the regulator and BCD all properly fit together. It is their first opportunity to understand how to read a submersible pressure gauge and the basics of why they had two separate second stages. They would soon be standing in chest-high water and for the first time awkwardly don their kit. The donning procedure may have begun as a buddy system teams helping each other to properly don their gear and perform gear checks or it may have begun as a solo event with each new diver learning how to properly don their own equipment, followed by performing buddy checks.

More often than not, the next step is for the instructor to check weighting, knowing that new divers breathe heavier, faster and using more of the aspiratory sector of the lungs. Understanding the above allowed the instructor to understand that in a matter of a few hours (and with a little guidance in how to properly breathe) buoyancy would change, thereby reducing the amount of weight a diver would need. When done correctly the above was explained to the new diver hence as a new divers breathing changed to a normal tidal volume, the new diver would more often than not be weighted perfectly for a tank that has been reduced to a third or less of its volume.

New divers have a tendency to exaggerate their inhalation and shortcut their exhalation but this improper breathing style will increase buoyancy as well as CO2 (1 litre of air equals approximately 1kg of buoyancy). Exhalation should be slightly exaggerated so that it is a little longer than inhalation.

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An example of what has been lost in contemporary diving training: monitoring diver breathing rates and quality, whether from topside or underwater, is one of the most critical accident prevention and early recognition procedures. All dive leaders should do this reflexively every time they see divers. All divers should reflexively monitor their own breathing rates and quality and should be aware of their buddy’s.

With proper breathing, scuba diving is more often than not a relaxed event.

When a new diver puts their head underwater for the first time it is the first time they ever really hear themselves breathe, so the tendency is to breathe heavier than normal, automatically increasing buoyancy.

Our job is to be aware of these things, so we can help them fix them and teach them how to breathe properly while manoeuvring and performing skills underwater.

The next few steps are to learn how to turn and stand with the tank and fins on, how to walk backwards and sideways, how to breathe without a mask, how to properly put a mask on, how to clear it underwater and breathe with a flooded mask, how to remove and recover second stage, how to adjust buoyancy. We then teach them how to roll over underwater or corkscrew, how to properly turn around underwater, how to communicate with hand signals and the basics of how to properly equalise. We teach them how to quietly and efficiently change body positions underwater on the bottom and in mid water, how to remove, replace and clear a face mask and adjust their gear efficiently anywhere in the water column. We not only want them to know how to use each and every piece of dive gear efficiently and to have basic buoyancy control, we want them to be confident in the interaction of all their underwater skills and equipment.

I personally always liked having students breathe without a mask on their first dive so that if they were going to

have a difficulty with it then I knew it right from the start and we could refine it immediately. Remember the actual skill as defined is: the diver will remove the mask underwater breathe for approximately one minute without a mask replace the mask and breathe with a flooded mask approximately one minute, then clear the mask while breathing on scuba. But how does all of this affect the use of a ditch and don?

When a new student diver had become proficient with many new skills, they were asked to connect all the skills in a series of underwater exercises. The ditch and don normally began with a buddy team donning equipment by the side of the pool. The instructor would observe the students dressing and monitor a proper buddy check. Each diver would then enter the deep end of the pool with an entry of their choice. At the surface a buddy pair would perform in water surface gear checks, just as they should perform on an open water dive prior to descent. The instructor would monitor a totally controlled descent to the bottom of the pool with equalising and descent rates performed properly. Upon arrival on the bottom both divers would do air checks and use proper hand signals to communicate, the same as a buddy team in open water. With the instructor immediately in front of them, he would issue a hand signal as to which of the buddy team would be the first to perform a slow and controlled demonstration of their ability to comfortably remove and replace the majority of their dive gear. With the instructor at less than a hands

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reach away, each diver would demonstrate their ability to comfortably remove and breathe without a mask, their ability to replace and clear it, and their ability to remove and recover their mouthpiece.

While demonstrating reasonable control at the bottom, without being over-weighted, the diver would slowly remove the BCD. As each student completed the skills they would perform an air check followed by an okay with their buddy. When both divers of the team were finished, they would demonstrate a controlled ascent of 10 metres per minute, at which point the buddy team would demonstrate a proper exit from the water.

When completed, the diver would still be in the same basic position as they were when they began, but this time having demonstrated they know how to move underwater, change balance within and without the BCD on their body and without thrashing their hands, arms, legs and fins in every direction.

Ditch and don was a eureka moment for many students.

After teaching diving for close to 50 years, and having been part of hundreds of meetings and discussions about what should or should not be taught at entry level courses, I’ve found that more often than not, pieces are not removed because they are unnecessary but rather because those pushing for that goal either cannot perform the skills themselves or cannot properly teach the skill.

Teaching often comes down, not to what’s really best for the student, but rather what is easier for the instructor and for those who are certifying new instructors. It seems we no longer take the time to teach new instructors how to teach or how to connect a series of positive building blocks in order to create comfortable, confident, reasonably reflexive students, but rather we give them tools that dictate what they teach and time restraints that restrict their ability to explore new teaching frontiers.

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Through my eyes

I recently spoke to a young instructor who asked if I could tell him what I would do in several situations. The conversation went something like this:

Him: “I am sure this has happened to you over the years: What do you do when you are taking a new diver to open water for the first time and you are extremely concerned that they are going to bolt?”

Me: “Why are you taking them open water if you were not 98% sure they are ready?”

Him: “The confined water part of the course is over and the standards say I am supposed to.”

This young instructor told me that he is so nervous before his students’ open water dives he does not sleep the night before.

Have I ever had a student attempt to bolt during an open water training dive? I’d be lying if I said no. Have I ever taken a student into open water if I thought for even a moment there was a good chance they were going to attempt to bolt? No, but I try to always plan for the unexpected.

Even when we have trained and rehearsed the open water training exercises in a confined water a dozen times my hands are still on the student, not only because the standards dictate this, but because it is part of my contingency plan – expect the unexpected.

We use the term “teach” so freely and yet often we discover that while we have told them what was needed to perform the skill correctly, we did not actually teach.

Let us examine one simple example. We are told to teach divers an ascent rate of 3-6 metres per minute and yet many divers of all different levels around the world ascend at much faster rates – commonly is fast as 20 metres per minute. Did we not tell them to move more slowly? We could tell them a dozen times, but each time we tell, we miss the opportunity to teach and we leave the student with no real understanding. How fast do you think the student is allowed to ascend or descend during the confined water training sessions, whether gradually following the bottom of the pool or making a straight ascent/descent? And do we, as instructors, set a good example of this?

Often students are simply chasing the instructor or assistant.

Basic confined water training is the time when students must learn to never move faster than their instructor. So it follows that instructors and assistants need to ensure they are never changing depth faster than 3-6 metres per minute.

Confined water dives are the perfect opportunity for us to teach a student to look at their submersible pressure gauge and make a mental note of every time they touch the bottom. Teach your students to make note of the time it takes to reach the surface prior to any kind of ascent. And lead by example. By doing this, the instructor will know that they have taught their students how to properly move, ascend and descend in the water column by the end of the pool sessions.

Don’t just tell your students that learning took place, teach them and show them. This way they have a far better chance of avoiding bolting for the surface and you can sleep at night before the open water dives!


By Walt 'Butch' Hendrick

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Contemporary instructors might tell you to always dive with a cutting tool to manage entanglements, but how many actually make sure you are physically able to cut fishing line and other items prior to certifying you as a diver? And of those very few instructors who do entanglement management hands-on training in entry level or any level of training – how many ensure that divers can use their cutting tools while wearing winter gloves in water with little to know visibility?

Severe barracuda bite during a night dive


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Warning: graphic images, reader discretion advised.


the aqua Med Emergency hotline received a call on the 21st July 2012 at 8:57pm. Christine l, an experienced scuba diver, had

been involved in a serious accident during a night dive in Egypt.

diagnosis: extended bite wound in the right knee joint and vascular injury caused by a barracuda. Ph

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Christine's logbook shows more than 650 dives and, up until now, no accidents. at the end of July 2012 she is on holiday in southern Egypt, on a safari boat.

On the 21st of July, a night dive is scheduled at one of the most remote locations of the tour, Saint John’s reef.

During the dive, a large and lone barracuda (Sphyraena barracuda) with a prey fish in its mouth suddenly swims at the edge of her light cone. Possibly irritated by the light, the barracuda lets go of its prey, a parrotfish, which swims towards Christine. The barracuda follows the fish, resulting in a huge bite. The bite causes three gaping wounds: two from the upper jaw on the ventral side of the knee and one from the lower jaw on the dorsal side in the popliteal fossa (knee pit). The quadriceps and distal patellar tendons are cut, the kneecap disintegrated and, from the dorsal wound, it is unclear which blood vessels have been injured. From the size of the jaw mark and wound, the length of the barracuda is estimated to be at least 1.5 metres.

“I only saw those big teeth coming towards me and I pushed the barracuda away with my torch. All of a sudden it came back from the left side and bit me on the right knee. I screamed in pain underwater and I do not know how I got out of there.”

Green fluid spreads through the water as blood pours from the wound. Christine's buddy quickly surfaces, calling the zodiac captain for help and Christine is pulled onto the boat, bleeding heavily. Luckily, the dive was kept shallow so there is little risk of decompression sickness from the rapid ascent.

As an Aqua Med client, Christine has the red dive card and emergency number attached and visible on her jacket. Because of this, the dive guides are able to quickly contact the Aqua Med Emergency Hotline via satellite phone. While the boat navigates towards the harbour, the Aqua Med doctor is able to support the local team and crew by giving important first aid instructions over the phone. And he is kept busy: How to apply a tourniquet correctly? How to position the patient? How to take her vital signs? What to do in case of a blackout? Although Christine is still conscious, she has lost a lot of blood, especially from the dorsal wound in the popliteal fossa.

In the meantime, the regional Aqua Med manager for Egypt has been contacted and is asked to organise medical care on land. This is a challenge in one of the most remote areas of Egypt, with few medical sites available, in the month of Ramadan. In this situation, time is precious so everything must be coordinated and planned speedily.

A non-stop bombardment of questions: What is the exact position of the boat? Which harbour is the closest? Where is the nearest

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'I only saw those big teeth coming towards me and I pushed the barracuda away with my torch. All of a sudden it came back from

the left side and bit me on the right knee. I screamed in pain underwater and I do

not know how I got out of there.'

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ground ambulance located? How well is it equipped and staffed? Is there an intensive care doctor we can send with the ambulance? Which is the closest and best-equipped hospital? Are there specialists in orthopaedic and vascular surgery available? Continual phone calls, coordination, consultations and organisation.

Travel time to the nearest harbour in Marsa Alam will take 3 hours, this is too long. The Aqua Med doctors and the captain decide to try the military harbour of Ras Banas (Port Berenice), which is considerably nearer. No stone is left unturned as they attempt to obtain authorisation for the safari boat and ambulance to enter the military zone.

Then, suddenly, the satellite phone connection fails.

Several anxious moments pass before the connection crackles back to life – it is not good news.

From the emergency protocol – 21st July 2012 – 23:07: “patient is unconscious and still bleeding, what should we do?”

Due to massive blood loss, Christine is in shock and has lost consciousness. Time is slipping away. Finally, they receive the

news they were hoping for: confirmed authorisation to enter Ras Banas!

It is vital to ensure professional medical stabilisation of the patient throughout the journey to the hospital. With the help of a well-established network built during many years of regional management in Egypt, a doctor is found in one of the hotels. He is picked up by the ground ambulance and they race to meet the boat in Ras Banas harbour, where yet another permission has to be obtained allowing the ambulance and medics into the harbour. During this time, another doctor specialising in knee surgery is recruited from Hurghada and begins the trip south to Port Ghalib Hospital.

Christine remembers, “I didn't feel any pain, the shock had been too big. I was not conscious of the seriousness of my injury. I thought it best not to look at it. I just wondered why everyone asked me whether I felt cold.”

The rendezvous between the safari boat and ambulance goes as smoothly as possible. Together with her dive buddy, Christine is taken to the hospital in Port Ghalib, located 200 kilometres north.

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A full cost breakdown is given to all medical practitioners involved in order to avoid time-consuming bureaucratic questions. Though requiring complex knee reconstruction and vascular surgery, thankfully the operation is a success. During her time in hospital, an Aqua Med doctor is in contact with both Egyptian colleagues and Christine by telephone on a daily basis to follow up on treatment and the rehabilitation. For her support, Christine’s dive buddy and partner is given accommodation at a nearby hotel. there an intensive care doctor we can send with the ambulance? Which is the closest and best-equipped hospital? Are there specialists in orthopaedic and vascular surgery available? Continual phone calls, coordination, consultations and organisation. Then, suddenly, the satellite phone connection fails.

Several anxious moments pass before the connection crackles back to life – it is not good news.

From the emergency protocol – 21st July 2012 – 23:07: “patient is unconscious and still bleeding, what should we do?”

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Due to massive blood loss, Christine is in shock and has lost consciousness. Time is slipping away. Finally, they receive the news they were hoping for: confirmed authorisation to enter Ras Banas!

It is vital to ensure professional medical stabilisation of the patient throughout the journey to the hospital. With the help of a well-established network built during many years of regional management in Egypt, a doctor is found in one of the hotels. He is picked up by the ground ambulance and they race to meet the boat in Ras Banas harbour, where yet another permission has to be obtained allowing the ambulance and medics into the harbour. During this time, another doctor specialising in knee surgery is recruited from Hurghada and begins the trip south to Port Ghalib Hospital.

Christine remembers, “I didn't feel any pain, the shock had been too big. I was not conscious of the seriousness of my injury. I thought it best not to look at it. I just wondered why everyone asked me whether I felt cold.”

The rendezvous between the safari boat and ambulance goes as smoothly as possible. Together with her dive buddy, Christine is

taken to the hospital in Port Ghalib, located 200 kilometres north. A full cost breakdown is given to all medical practitioners involved in order to avoid time-consuming bureaucratic questions. Though requiring complex knee reconstruction and vascular surgery, thankfully the operation is a success. During her time in hospital, an Aqua Med doctor is in contact with both Egyptian colleagues and Christine by telephone on a daily basis to follow up on treatment and the rehabilitation. For her support, Christine’s dive buddy and partner is given accommodation at a nearby hotel.

One week later, Christine gets the okay to fly from Egyptian doctors and repatriation to Germany is organised. In the company of her partner – and with the help of a ground ambulance and wheelchair service – the journey is made as easy and comfortable as possible. She is brought to the Sportklinik at Markgröningen near her hometown in Stuttgart. Prior to her arrival, the hospital was contacted and all necessary medical notes were transferred to ensure that follow-up treatment and rehabilitation run smoothly. As the infection risk after a maritime bite is usually high, Christine is hospitalised for a couple of days and given additional antibiotics through an IV. Further diagnostics (MRI, CT and X-rays), as well as the clinical findings in Germany, show that the performance of the Egyptian doctors was top-notch.

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However, such was the severity of the injury, that it would take months of tiring physiotherapy and personal training to achieve a sufficient range of movement, muscular function and a normal physiological gait pattern. Also, during the rehabilitation process, a small granuloma caused by a tiny remaining stitch would have to be removed.

Beyond the physical impact, Christine has also had to overcome the psychological trauma of such an accident and I am pleased to say that she has – Christine is once again diving in the Red Sea!

Christine has been diving since 1992, most of the time without any diving insurance. This accident clearly demonstrates the importance of good medical coverage and effective assistance in case of an emergency.

Christine agrees, “I was really positively surprised by the benefits included in this small red card. The assistance of the hotline doctors from the first call until the last operation here in Germany was overwhelming. I hadn't expected such absolute commitment. That gave both my buddy and I a feeling of great security the whole time.”

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Learning from Experience :

this incident involved an experienced diver having an issue on descent to a deep wreck due to running out of diluent, this is despite them using a checklist." (note: the images in this article are not of the diver involved!). The dive was to take place 25 miles off shore from a hard-deck boat and was the first boat dive in more than six months, although it is assumed that shore dives on the CCR had taken place during that period.

The diver had personally filled, analysed and marked their cylinders two days prior to the event and the pressure of both cylinders at that time was 230 bar. The CCR was assembled using the unit specific checklist provided by the manufacturer.

On the day of the dive, the unit was placed on the boat and strapped down as per their normal practice. On arriving in the site area, the diver got kitted up with two Aluminium 11 litre bailout cylinders that were rigged as per their normal practice.

The diver then opened the Diver Supply Valve (DSV) to start their pre-breathe sequence and noticed that the counter-lungs were overly full. The diver exhaled to vent the lungs. They also noticed that the solenoid was continually firing to reach a Set Point (SP) of 0.7. This behaviour was unusual for the unit, although it settled down after a little while.

The diver then carried on through their pre-dive checks, the unit worked so the divers entered the water to start the dive. They did a bubble check at six metres and all appeared to be fine. The diver added diluent at six metres and the unit still appeared to be working normally. They then started their descent and, as they passed 15 metres, experienced difficulty breathing. Their immediate reaction was to add diluent, which they did before continuing to descend.

At 25 metres the diver stopped on the shotline, finding themselves unable to breathe. They pressed the Manual Add Valve (MAV) and no diluent was added. They then checked the diluent cylinder contents gauge and it was empty. They rapidly plugged in their deep bailout cylinder to the MAV, which immediately resolved the issue and

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By Gareth Lock

Closed Circuit Rebreather unit out of diluent at depth

"They then started their descent and, as they passed 15

metres, experienced difficulty breathing"

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everything returned to normal. Assessing the rest of the unit functionality (five good cells, good scrubber, plenty of O2 and plenty of diluent in the bailout), they continued the dive without event.

The diver described the dive as unenjoyable because they had lost a full cylinder of diluent somewhere between kitting up and jumping in and this played on their mind, potentially causing a distraction.

They spent the next two weeks not diving the CCR and trying to break down the incident until they were happy they understood what had happened. This is their technical analysis, my analysis of human factors follows. diver’s analysis

“When I built the unit the previous day I forgot to turn off the diluent cylinder. Fast forward to the day of the dive when I am strapping the unit onto the seat of the boat. The diluent MAV button was being pressed under the strap but, beneath the roar of the boat’s diesel engines, I never heard my unit’s OPV (Over Pressure Valve) continually firing. When we got to the site there was still about 10-15 bar of diluent left in the cylinder, which is why when I tested the MAV and wing inflate both worked fine and why when I added diluent at six metres they also worked fine. It was not until I passed 15 metres, when the absolute pressure was 2.5 bar, did the internal remaining pressure balance against the external pressure causing no supply of diluent. “A deep dive 25 miles off shore is not a good first boat dive of the year. Why did I not check my diluent contents when I put the unit on my back? Complacency because I had filled the cylinder 48 hours previously and marked it up as 230 BAR OF 12/60. I then assumed it was still full, especially when it delivered diluent to the MAV and wing at the start of the dive.

To conclude: complacency and diver error”

Expert analysis

A number of errors and mistakes took place on this dive, but there was also some great work to try and minimise potential failures. Here is my analysis of the situation and what can be done to improve things further.

1. Building the unit with a checklist is a great idea and should be something everyone does. However, the unit checklist requires the dil cylinder to be shut off prior to a negative check. Using a checklist is great, but you need to follow all of the steps otherwise you may place yourself in an unstable state, assuming that the unit is in one configuration when it is not. The pre-jump checks then start with “dil open, pressure check” which would have also picked up a different configuration to expected. Humans make many errors where we think, sometimes convincing ourselves, that we have done something. It is only when something else is triggered that we recognise the error.

2. Situational awareness is defined as the ability to notice something, think about its impact or consequences, then anticipate what might go wrong.

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While the diver did recognise that the lungs were full, they did not think why this could be the case or what the potential implications were. If something is out of the ordinary or has changed, try to think why this changed state has happened. In addition, had they started the pre-jump check of opening the dil they would have noticed it was already open. On the descent, it was hard to breathe – why? Was the ADV not firing properly? You have noticed something so think about what it might mean. Anticipate the future.

3. During the pre-breathe I personally go through the items on a handwritten checklist in my wetnotes, items that I am going to brief my teammate as part of the pre-dive brief. This starts on the bottom right for my JJ unit, working through cylinder valves, pressures, inlet valves and dumps, and then moves to the bottom left and back up, with gases set in the controller, set points set in the controller and whether it is tracking with high and low SP, making sure the HUD (Heads-Up Display) matches the controller, and again ensuring dumps and inlet valves all work. At this stage a problem with low diluent pressure would have also been noticed. At the briefing stage, I go through these items but do not check them, just read through the pre-dive brief. Having a structured brief that is followed every time allows my teammate to check whether I have missed something I did not mention. This takes discipline, obviously a teammate to dive with, and courage because you will be different.

4. It is good to be diving with a buddy and using them for the bubble check on descent, however, it is not clear whether that buddy remained for the duration of the dive. As shown here (https://cognitasresearch.wordpress.com/2014/06/17/tying-a-bow-to-manage-risk/), a buddy can help spot and resolve issues prior to the event, as well as help out if or when things do go wrong.

5. The internal critical analysis is great to see. Too many divers just leave it at that and do not try to analyse what went wrong, why it went wrong and what could be improved, with a view to preventing the same thing from happening. It is also great to see that the diver reported the incident to DISMS (www.divingincidents.org) so that others could learn from the event.

6. Complacency is a catch-all phrase for when the mental models we hold about the world do not match the reality of what is in happening in front of us. We use heuristics (mental shortcuts) all the time to allow us to be efficient in time, but maybe not so thorough. This means sometimes we miss vital cues about what is really happening, with an increased risk of an adverse event occurring as a consequence.

Summary The ability to anticipate within situational awareness is normally developed through direct or indirect learning, and no doubt this diver will not make this same mistake again. Now that you have read this, my hope is that you will make a mental note to follow a structure and if something is out of the ordinary, you will then notice, think, anticipate and resolve the minor issue before it becomes a major one. This is not just about CCR diving, it is about any activity in life. Small changes are hard to spot, but they can easily snowball into unmanageable, life-threatening situations.

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Unexpected air pockets: The importance of good oral health for divers

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the diverA 40 year old male with more than 1500 dives, no known medical conditions and a healthy lifestyle.

In the months before this incident, the diver had multiple root canal treatments and other major dental work. In the week preceding the incident he made several decompression dives on a rebreather using a scooter without any problems.

the incident On his last dive of a week-long series, the diver felt a momentary dull pressure and pain in his lower teeth during descent; he dismissed it since the pain seemed to vanish as he continued descending to a maximum depth of 47 metres. When he started to ascend after spending 30 minutes at 41 metres, he experienced sharp and severe pain in the same teeth. After ascending an additional two metres, the diver became aware that several dental fillings had come loose. As he continued his ascent, two fillings fell apart and came out of his teeth. He halted the ascent for a few minutes to compose himself and assess how to reach the surface safely.

To avoid further complications and prevent the dental-filling debris from damaging the bailout valve of his rebreather, he switched to his backup open circuit unit and spat out the filling fragments. He then returned to the closed circuit loop to conserve gas. His dive buddy was attentive and assisted him with his scooter and reel throughout the ascent. The diver stayed at 29 metres for 10 minutes to deal with the excruciating pain he felt throughout his lower teeth before continuing a safe ascent to the surface.

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the diagnosisSeveral days after the incident the diver went to his dentist, who suggested that biting too hard on the regulator mouthpiece had generated pain similar to that caused by a grinding or clenching of the teeth. However, diagnostic X-rays showed the amalgam fillings in five of the diver’s teeth were either damaged or missing entirely. Defective fillings may have allowed air to enter between the filling and the tooth and become trapped. During ascent the trapped air expanded and created pressure against the internal structures of the tooth, which triggered the tooth pain and caused two of the fillings to fall out.The dentist replaced the damaged fillings, but the diver continued to experience tooth pain when diving. He sought a second opinion from another dentist, who identified through further X-rays that there were problems with the fillings of four teeth and recommended replacement. The diver had the fillings replaced and returned to diving without experiencing further pain.

This was a case of barodontalgia (tooth pain caused by change in ambient pressure), also known as dental barotrauma.

"Diagnostic X-rays showed the amalgam fillings in five of the diver’s teeth were either damaged or missing entirely"

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Phot

o by

Rad

u Be

rcan

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discussionAs a diver descends into the water, the ambient pressure increases by one atmosphere every 10 metres. This pressure change affects body cavities such as the ears and sinuses by creating unequal pressures between the cavity and the ambient environment. This is relieved by equalising the pressure. When a tooth is damaged, restored defectively or has a loose crown, an opening may allow air to enter into the space and become trapped during a dive with no way for the diver to equalise it. The diver may experience tooth pain during descent, when pockets of air that exist under defective fillings are compressed, or during ascent as the trapped air expands. This expansion may loosen or expel fillings and crack teeth.

In this case, the diver had tooth pain on ascent due to defective fillings, which subsequent dental diagnostics confirmed. The unusual aspect of this case was that a total of five teeth appeared to have been affected on the same dive, two of which expelled their fillings during the dive. Barodontalgia generally originates with poor oral health, neglected dental maintenance and/or ineffective dental treatments. Of the 347 total cases of barotrauma reported in the 2008 edition of the DAN Annual Diving Report, two cases were categorised as barodontalgia. Although considered a rare occurrence, barodontalgia should not be dismissed; the severe pain can lead to potential safety risks such as rapid ascents and impaired judgement. This case may be extreme, but it serves as a reminder that being fit to dive requires a holistic approach that includes dental health. It is not necessary to seek a dentist specifically trained in dive medicine for dental checkups; rather it is important to routinely visit a dentist that provides quality care so you can be confident your dental health is maintained. The FDI World Dental Federation advises that divers have regular dental checkups, refrain from diving (or flying in non-pressurised cabins) within 24 hours of any dental treatment that requires anaesthetic and within seven days of an oral surgical procedure.Fillings are prone to deterioration over time. Semi-annual dental checkups allow your dentist to inspect existing fillings for damage and to detect and treat tooth decay quickly. By maintaining good oral health, divers can avoid barodontalgia and keep their post-dive smile.

AlertDiver.eu, 2014; 56

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"Barodontalgia generally originates

with poor oral health, neglected dental

maintenance and/or ineffective dental

treatments"

Phot

o by

Yan

Lev

Diver Medic and Aquatic Safety Issue 5 Aug 2015

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Transcript of Diver Medic and Aquatic Safety Issue 5 Aug 2015