Dive Medicine and Hyperbaric Therapy

ObjectivesReview physics of compressed air divingComplications during descentMedical problems at depthComplications during ascentPrevention of complicationsPrehospital care of dive injuriesHyperbaric therapy for dive injuriesCase ReportVeteran police diver is pulled from the water with no vital signs during a training exerciseThe 50-year-old diver signalled her partner that she had encountered some sort of difficultyThe partner pulled the officer back into the boat and began administering CPR enroute back to landOn arrival, paramedics encounter a female police officer with no vital signsThe partner, a 48 year old male officer is short of breath and complaining of back pain Your next steps?What do you want to know?What do you want to do?What triage decisions do you make?What resources do you need?

A brief history of divingBreath-hold diving for food and resources for thousands of yearsEvidence of Neanderthal divers 40,000 years agoFires built by Fuegian Indian divers in Straits of Magellan to warm themselves (hence Tierra del Fuego)Ancient Greece and Persia recorded military use of diving bells (e.g. to cut anchor cables, bore holes in ships)

Compressed air divingMid-1800s first practical surface-supplied diving suitFrench engineers pioneer compressed air to keep underwater chambers dry for work on bridge footings1943 Cousteau and Gagnon invent SCUBAPresently has recreational, scientific commercial, and military applicationsEnhancements: rebreather systems, mixed gas diving...A word from our sponsor

PhysicsResistance is Futile.

Sea level1 ATM10 m2 ATM20 m3 ATM30 m4 ATMEffects of ambient pressure

Boyles Law:As ambient pressure increases,volume decreases

SCUBA delivers increasing amounts of gas to maintain normal volume against ambient pressureDive Medicine and Hyperbaric TherapyDr. Michael FeldmanSunnybrook-Osler Centre for Prehospital CareHenrys Law

Descent

Increased pressure increases dissolvedgasAscent

Dissolved gas comesout of solution andis exhaledDescentAmbient pressure increases tremendouslyBody tissues act as a non-compressible fluid and the force is not perceptibleGas-filled spaces (sinuses, middle ear, lung, gastrointestinal tract) are compressibleLung is filled with SCUBA-supplied gas at increased pressures, which resists the compressive force of waterIncreased partial pressures in lungs responsible for increased dissolved gases in the bloodstreamBarotrauma of DescentMask barotraumaSinus barotraumaExternal ear barotrauma (if air is trapped by hood)Barotitis mediaInner ear barotrauma (round or oval window can be ruptured by either increased pressure in middle ear or forceful Valsalva maneuver)Suit squeezeDental barotraumaLung squeeze (breath-hold divers, >30 m depth)Mask BarotraumaAs diver descends, air must be added toairspace between mask and faceIf the diver forgets, periorbital edema,ecchymosis, and subconjunctivalhemorrhage may resultThis is usually benign despite the dramatic appearance

Sinus barotraumaIf any of the sinuses are blocked, a relative vaccuum developsPatient presents with severe pain in the affected sinus (usually frontal sinus)On ascent, the expanding gas may result in expulsion of blood and mucous into the nose and maskBarotitis MediaDuring descent, pressure in the middle ear must be equalized at regular intervalsDiver may experience ear pain as water pressure distorts the tympanic membraneRupture of tympanic membrane will relieve the pain, but may be accompanied by severe vertigo as cold water enters the middle ear

Lung SqueezeRare complication in breath hold divingNo limits diving mens world record 172 m; womens record 160 mWell-documented dive in which a Belgian diver flooded his sinuses and eustachian tubes during descent; reached 210 mLungs get compressed to very small volumes, causing pulmonary edema

Complications at DepthNitrogen narcosis increased dissolved nitrogen acts as an intoxicant, possibly by altering electical properties of excitable membranesBegins at 20-30 m: euphoria, deterioration in judgment70-90 m: auditory and visual hallucinations120 m: loss of consciousnessTreated by ascentPrevented by heliox commercial diving gas mixturesOxygen ToxicityPulmonary toxicityCan cause alveolar damage and pulmonary edemaNot a problem in diving (but a consideration in hyperbaric chambers breathing 100% O2 at 3 ATM)CNS toxicityOccurs when breathing 100% O2 at high ambient pressuresCauses oxygen-induced seizures in hyperbaric chambersTreatment: removal of supplemental O2AscentDecreased ambient pressure allows gas-filled spaces to expandDecreased partial pressure of gases in lungs allows dissolved gases to come out solutionBubbles form in tissuesPressure in lungs forces air across alveolar membraneAlveolar rupturePulmonary BarotraumaExpansion of trapped alveolar gas (e.g. against a closed glottis)Divers usually have a history of rapid or uncontrolled ascent (out of air, uncontrolled positive buoyancy)A pressure difference of 80 mmHg (1 m ascent) is sufficient to force air across pulmonary alveolar membrane into interstitial space or vascular systemMay result in pneumothorax, pneumomediastinum, pneumoperitoneum, or arterial gas embolismPulmonary Overpressurization26 year old naval seamanOne hour dive between 3 and 10 m depthsChest pain, neck swelling, hoarse voice immediately on surfacingTreated with 100% O2; resolved within 2 days without sequelae

Arterial Gas EmbolismThe most dramatic injury associated with compressed air divingAir bubbles forced into pulmonary microcirculation and through to left atrium, where they are dispersed to arterial circulationResult in mechanical occlusion of small arteries and disruption of BBB resulting in cerebral edemaClinical presentation is usually sudden and dramaticAnyone who has neurologic symptoms or loss of consciousness within 5 minutes of surfacing should be presumed to have AGECerebral Arterial Gas Embolism42 year old recreational diver with 2 years experienceSeen to have suddenly surfacedWhen reached by the boat, he had no vital signs. His air tank was empty and his buoyancy compensator fully inflatedCPR started immediately, with return of circulation 12 minutes laterSeizures and decorticate posturing in EDHyperbaric treatment (USN table 6A) for 7 hoursNow confined to wheelchair; able to carry out most ADLsCerebral Arterial Gas Embolism

Decompression Sickness IPain in joints with the consequent loss of function The pain often described as a dull ache, most common in shoulders or knees The pain is initially mild and divers may attribute early DCS symptoms to overexertionSkin bends: rashes, mottling, itching and lymphatic swelling

Decompression Sickness IICNS, pulmonary, or circulatory involvementSpinal cord is the most common site for Type II DCSLow back pain may start within minutes and may progress to paresis, paralysis, paresthesias, and loss of sphincter controlOther symptoms may include headaches, visual disturbances, dizziness, and changes in mental status or cognitionLabyrinthine DCS (the staggers) causes nausea, vomiting, vertigo, nystagmus, tinnitus and hearing loss. Labyrinthine disturbances not associated with other symptoms of DCS likely due to barotraumaPulmonary DCS (the chokes) causes (1) substernal discomfort, (2) non-productive cough, and (3) respiratory distressHypovolaemic shock fluid shifts from intravascular to extravascular space

Prevention of Decompression SicknessLimit time spent at depthSlow and staged ascents (decompression stops) so that bodys burden of nitrogen is eliminated without forming bubblesUSN and commercial dive tablesDive computers to track dive profile and calculate decompression requirementsAvoidance of flight for 24 hours after last diveProtective effect of vigourous exercise USN Navy Dive Table

Prehospital Care of Diving Injuries100% O2 to facilitate washout of N2Crystalloid infusion maintains capillary perfusion for elimination of bubblesDiazepam may relieve labyrinthine vertigo (if not responsive to dimenhydrinate)ASA (bubbles may cause platelet aggregation)ALS procedures as appropriate (e.g. needle decompression)Transport to hyperbaric facilityHyperbaric Oxygen TherapyToronto hyperbaric chamber at UHN General siteMultiplace chamber can dive to 2 to 5 ATMOther Ontario chambers in Hamilton, Ottawa, TobermoryAccess via DAN or Criticall

HBOT - IndicationsAir or gas embolism Carbon monoxide poisoning cyanideClostridal myositis (gas gangrene) and necrotizing soft tissue infectionCrush injury, compartment syndrome (acute traumatic ischemia) Decompression sickness Problem wound healing Exceptional blood loss (anemia) Intracranial abscess Osteomyelitis (refractory) Delayed radiation injury (soft tissue and bony necrosis) Compromised skin grafts and flaps Thermal burns and frostbite

Recompression Treatment

Air breathingO2ObjectivesReview physics of compressed air divingComplications during descentMedical problems at depthComplications during ascentPrevention of complicationsPrehospital care of dive injuriesHyperbaric therapy for dive injuriesQuestions?