Diving Medicine

Sgn Cdr John Duncan, RNZN

Director of Naval Medicine

Navy Hospital

Slark HBU

HMNZS MANAWANUI

Diving records• 7200 ft and submerged for

two hours

• 2000ft and submerged for an hour

• Free diving ~100m

• No limits 214 Meters

Caisson Disease

Haldane

• 1905-1907 Haldanes work

•Five compartment model•2:1 Ratio•Research with goats•Refined on divers•Ironically a lot of divers today behave like goats•Still basis of tables today

Goat Picture

http://www.scubadiverinfo.com/images/dive_tables_PADI_front.jpg

Dive Profile

-30

-25

-20

-15

-10

-5

0

1 2 3 4 5 6 7

Depth

Tim

e

Diver Numbers

Diver Numbers Slark Hyperbaric Unit

0102030405060708090

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Number

Ye

ar

CAGE - cerebral arterial gas embolism

• Air trapped in lung may expand and burst into arterial system via pulmonary veins – goes to brain

• Massive bubble load may cross to pulmonary veins through lungs – goes to brain

• Presents with rapid onset neurological symptoms

• Patients often recover, then deteriorate

Decompression illness

• Bubbles form in tissue/blood from dissolved N2

on ascent if time / depth of dive was too great, and ascent is too fast

• DCI can be avoided by very slow ascent (but this is sometimes too slow to be practical)

• Bubbles damage vessels and tissue• Variable presentation - pain, weakness, feeling

‘off colour’, breathlessness

16

DECOMPRESSION ILLNESS- evolution of bubbles from dissolved nitrogen

Air breathed at greater pressure during dive Gas solubility increased at greater pressure N2 absorbed into blood and tissues

Amount of gas depends on time and depth N2 solubility declines during ascent (as pressure decreases)

Bubble formation - tissues and blood

17

RISK FACTORS FOR DCI

Too deep / too long – exceed table limits• Rapid ascent• Omitted decompression• Repetitive diving (multiple ascents)• “Bounce dives”• Flying after diving – no flying for 24 hours• Age

RISK FACTORS FOR DCI 2

• Inter-current illness, cold, working hard, etc.• Panic• Gear Failure• Poor planing

Bubbles

tissues

venous blood (some bubble formation)

lungs

*

off-gas arteries organs

Tissue bubbles

• Mechanical effects– compression– stretch

• myelin sheaths, bone, spinal cord, tendon, etc

• Biochemical– activation of complement– coagulation– kinins

Effects

• Reduced microcirculation– ischaemia (haemorrhagic or thrombotic)

– vessel permeability– oedema– inflammation

22

DECOMPRESSION ILLNESS - presentation of disease• Marked variation, from mild constitutional

symptoms to paralysis• Most cases apparent within 24 hours• Only 50% have objective signs• Worst cases are early onset with

progressive neurological symptoms• Diving may not reflect severity• Neurology may not “make sense”

Classification

• Decompression sickness– Type I - musculoskeletal, skin, lymphatic,

constitutional

– Type II - neurological, cardiorespiratory, vestibular

• Arterial gas embolism• Barotrauma

Little diagnostic or prognostic significance

Current classification

• Decompression illness– acute or chronic– static, progressive, relapsing, spontaneously

resolving– organ system involved (cutaneous, cerebral,

spinal, musculoskeletal, lymphatic, etc)– +/- barotrauma

Differentiating between pathological processes

• Decompression illness - due to inert gas load and bubble evolution….

• Barotrauma

• Other diving-related illness

• Depth-time profile gives indication of inert gas load

• Pattern of dive - no. and speed of ascents, etc

• Time of onset of symptoms

• Symptom evolution

• Signs

Making a diagnosis

Cerebral emboli - CAGE

• Usually rapid onset on surfacing

• Loss of consciousness or fitting

• Victims may drown

• Spontaneous recovery of consciousness

• Apparent resolution, then deterioration

Symptom frequencySymptoms after diving are common, DCI is

not• Pain 40%

• Altered sensation 20%

• Dizziness 8%

• Fatigue, headache, weakness 5%

• Nausea, SOB 3%

• Altered LOC 2%

• Rash < 1%

29

DECOMPRESSION ILLNESS classical vs typical patients

THE ‘CLASSICAL’

PATIENT• Exceeds time / depth• Rapid onset of pain• Followed soon after by

weakness and sensory changes

• Presents early

THE ‘TYPICAL’

PATIENT• Borderline time / depth• Initially well• Later, migratory aches,

feels “off colour” and tired• Seeks help several days

after diving

30

DECOMPRESSION ILLNESS - presentation by system

Constitutional Musculo-Skeletal

Skin Heart / Lungs Neurological

“(Anything)”

Fatigue Pain Rash Cough Weakness

Malaise - joints Itch Dyspnoea Sensory change

“Off colour” - limbs Chest pain Bladder and bowel

- girdles

Assessing a diver• A, B, C and if conscious and talking – start

oxygen @ 4L/minute, take blood pressure and pulse

• RECORD EVERYTHING – TIME, etc• Dive profile – depth, time, gas, any events• When did they first notice symptoms?• What were they?• What has happened to the symptoms since?• How do they feel now?• When did they last pass urine?

32

DECOMPRESSION ILLNESS- evaluation in first aid

BRIEF HISTORY BRIEF EXAMINATION

Depth(s) / time(s) Vital signs

Number of ascents Chest

Nature of ascents Neurological

Nature of dive

Symptoms

Temporal relation of

symptoms to dive

Be suspicious if there is any history of altered consciousness, even if transient –

this might be CAGE, which is serious

Refer for treatment

diving emergency services

D.E.S. number (09) 4458454

D.E.S. service• Available 24/7• Call will be answered by Navy Hospital staff -

get basic details• Give contact number• Experienced doctor & consultant on call• Response:

– advice on initial management– transfer immediately (St John coordinate) OR – assess at local hospital OR– review next day

35

DECOMPRESSION ILLNESS - steps in DCI first aid

• ABCs• Position• Oxygen• Fluids• Evaluate• Contact D.E.S.• Evacuate

36

DECOMPRESSION ILLNESS - positioning in first aid

CURRENT ADVICE

• Horizontal• Recovery position if LOC

is decreased• Previous advice was

head down

THE CASE AGAINST

HEAD DOWN• Difficulty• Oral fluid administration

• Increase ICP and cerebral oedema

• Arterialisation of venous bubbles

37

DECOMPRESSION ILLNESS - oxygen in first aid

CURRENT ADVICE RATIONALE

100% Oxygen: damaged valve;

bag/mask/reservoir

Promote N2 outgassing

Record time on / any time off / clinical effects

Promote bubble resolution

Oxygenate ischaemictissue

38

DECOMPRESSION ILLNESS - IV fluids in first aid

CURRENT ADVICE

RATIONALE

0.9% NaCl 1000 ml stat and 100-250 / hr

Divers are usually dehydrated

Titrate against output in long evacuations

DCI= a compromise of the microcirculation

Record fluid balance DCI and dehydration are a bad combination

may need catheter

Adjunctive treatments

• Possible benefit:– NSAIDs (oral, IM)– lignocaine (IV infusion)

• Of no benefit:– heparin or other anticoagulants– steroids

40

DECOMPRESSION ILLNESS- evacuation in first aid

• Not always necessary• Advice from D.E.S. is usually sought first• Minimise altitude – either road, or fixed wing at

normal atmospheric pressure (1 ATA), or rotary (but <300m)

• Maintain oxygen administration• Maintain horizontal posture in acute cases• Avoid pain relief• No entonox

Helicopter vs fixed wing

HELICOPTER• Noisy• Poor access to

patient• Unpressurised• Ideal for short coastal

distances• Good for isolated

areas, boats

FIXED WING• Quieter• Better access

• May be pressurised• Ideal for long haul

over high country• Limited if no strip

Summary: initial management• CPR if necessary• Oxygen - 100% if possible (need rebreather)

• Lie flat• Get advice• Rehydration (fluid balance)

– oral or IV crystalloid– 1L stat, 1L 4-6 hrly

• Evacuate for recompression• NSAIDs if needed

Recompression treatment

• Recompress diver to depth – can use oxygen or oxygen-helium

• bubble compression• increase diffusion gradient so gas leaves

bubble• counter effects of pulmonary AV shunting• deliver high oxygen tensions to damaged

tissue

Recompression therapy

18m

30min

9m

1hr

2hrs surface (0m)

= air ‘breaks’ to reduce oxygen toxicity

(and for convenience, comfort, etc)