Objectives

1. Objectives • Review physics of compressed air diving • Complications during descent • Medical problems at depth • Complications during ascent • Prevention of complications • Prehospital care of dive injuries • Hyperbaric therapy for dive injuries

2. Case Report • Veteran police diver is pulled from the water with no vital signs during a training exercise • The 50-year-old diver signalled her partner that she had encountered some sort of difficulty • The partner pulled the officer back into the boat and began administering CPR enroute back to land • On arrival, paramedics encounter a female police officer with no vital signs • The partner, a 48 year old male officer is short of breath and complaining of back pain

3. 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?

5. A brief history of diving • Breath-hold diving for food and resources for thousands of years • Evidence of Neanderthal divers 40,000 years ago • Fires 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)

6. Compressed air diving • Mid-1800’s – first practical surface-supplied diving suit • French engineers pioneer compressed air to keep underwater chambers dry for work on bridge footings • 1943 – Cousteau and Gagnon invent SCUBA • Presently has recreational, scientific commercial, and military applications • Enhancements: rebreather systems, mixed gas diving

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8. Sea level 1 ATM Effects of ambient pressure Boyles Law: As ambient pressure increases, volume decreases SCUBA delivers increasing amounts of gas to maintain normal volume against ambient pressure 10 m 2 ATM 20 m 3 ATM 30 m 4 ATM

9. Dive Medicine and Hyperbaric Therapy Dr. Michael Feldman Sunnybrook-Osler Centre for Prehospital Care

10. Henry’s Law

11. Ascent Dissolved gas comesout of solution andis exhaled Descent Increased pressure increases dissolvedgas

12. Descent • Ambient pressure increases tremendously • Body tissues act as a non-compressible fluid and the force is not perceptible • Gas-filled spaces (sinuses, middle ear, lung, gastrointestinal tract) are compressible • Lung is filled with SCUBA-supplied gas at increased pressures, which resists the compressive force of water • Increased partial pressures in lungs responsible for increased dissolved gases in the bloodstream

13. Barotrauma of Descent • Mask barotrauma • Sinus barotrauma • External ear barotrauma (if air is trapped by hood) • Barotitis media • Inner ear barotrauma (round or oval window can be ruptured by either increased pressure in middle ear or forceful Valsalvamaneuver) • Suit squeeze • Dental barotrauma • Lung squeeze (breath-hold divers, >30 m depth)

14. Mask Barotrauma • As diver descends, air must be added toairspace between mask and face • If the diver forgets, periorbital edema,ecchymosis, and subconjunctivalhemorrhage may result • This is usually benign despite the dramatic appearance

15. Sinus barotrauma • If any of the sinuses are blocked, a relative vaccuum develops • Patient 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 mask

16. Barotitis Media • During descent, pressure in the middle ear must be equalized at regular intervals • Diver may experience ear pain as water pressure distorts the tympanic membrane • Rupture of tympanic membrane will relieve the pain, but may be accompanied by severe vertigo as cold water enters the middle ear

17. Lung Squeeze • Rare complication in breath hold diving • “No limits” diving – men’s world record 172 m; women’s record 160 m • Well-documented dive in which a Belgian diver flooded his sinuses and eustachian tubes during descent; reached 210 m • Lungs get compressed to very small volumes, causing pulmonary edema

18. Complications at Depth • Nitrogen narcosis – increased dissolved nitrogen acts as an intoxicant, possibly by altering electical properties of excitable membranes • Begins at 20-30 m: euphoria, deterioration in judgment • 70-90 m: auditory and visual hallucinations • 120 m: loss of consciousness • Treated by ascent • Prevented by heliox commercial diving gas mixtures

19. Oxygen Toxicity • Pulmonary toxicity • Can cause alveolar damage and pulmonary edema • Not a problem in diving (but a consideration in hyperbaric chambers – breathing 100% O2 at 3 ATM) • CNS toxicity • Occurs when breathing 100% O2 at high ambient pressures • Causes oxygen-induced seizures in hyperbaric chambers • Treatment: removal of supplemental O2

20. Ascent • Decreased ambient pressure allows gas-filled spaces to expand • Decreased partial pressure of gases in lungs allows dissolved gases to come out solution • Bubbles form in tissues • Pressure in lungs forces air across alveolar membrane • Alveolar rupture

21. Pulmonary Barotrauma • Expansion 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 system • May result in pneumothorax, pneumomediastinum, pneumoperitoneum, or arterial gas embolism

22. Pulmonary Overpressurization • 26 year old naval seaman • One hour dive between 3 and 10 m depths • Chest pain, neck swelling, hoarse voice immediately on surfacing • Treated with 100% O2; resolved within 2 days without sequelae

23. Arterial Gas Embolism • The most dramatic injury associated with compressed air diving • Air bubbles forced into pulmonary microcirculation and through to left atrium, where they are dispersed to arterial circulation • Result in mechanical occlusion of small arteries and disruption of BBB resulting in cerebral edema • Clinical presentation is usually sudden and dramatic • Anyone who has neurologic symptoms or loss of consciousness within 5 minutes of surfacing should be presumed to have AGE

24. Cerebral Arterial Gas Embolism • 42 year old recreational diver with 2 years experience • Seen to have suddenly surfaced • When reached by the boat, he had no vital signs. His air tank was empty and his buoyancy compensator fully inflated • CPR started immediately, with return of circulation 12 minutes later • Seizures and decorticate posturing in ED • Hyperbaric treatment (USN table 6A) for 7 hours • Now confined to wheelchair; able to carry out most ADLs

25. Cerebral Arterial Gas Embolism

26. Decompression Sickness I • Pain 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 overexertion • Skin bends: rashes, mottling, itching and lymphatic swelling

27. Decompression Sickness II • CNS, pulmonary, or circulatory involvement • Spinal cord is the most common site for Type II DCS • Low back pain may start within minutes and may progress to paresis, paralysis, paresthesias, and loss of sphincter control • Other symptoms may include headaches, visual disturbances, dizziness, and changes in mental status or cognition • Labyrinthine DCS (the staggers) causes nausea, vomiting, vertigo, nystagmus, tinnitus and hearing loss. Labyrinthine disturbances not associated with other symptoms of DCS likely due to barotrauma • Pulmonary DCS (the chokes) causes (1) substernal discomfort, (2) non-productive cough, and (3) respiratory distress • Hypovolaemic shock – fluid shifts from intravascular to extravascular space

28. Prevention of Decompression Sickness • Limit time spent at depth • Slow and staged ascents (decompression stops) so that body’s burden of nitrogen is eliminated without forming bubbles • USN and commercial dive tables • Dive computers to track dive profile and calculate decompression requirements • Avoidance of flight for 24 hours after last dive • Protective effect of vigourous exercise

29. USN Navy Dive Table

30. Prehospital Care of Diving Injuries • 100% O2 to facilitate washout of N2 • Crystalloid infusion – maintains capillary perfusion for elimination of bubbles • Diazepam 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 facility

31. Hyperbaric Oxygen Therapy • Toronto hyperbaric chamber at UHN General site • Multiplace chamber can dive to 2 to 5 ATM • Other Ontario chambers in Hamilton, Ottawa, Tobermory • Access via DAN or Criticall

32. HBOT - Indications • Air or gas embolism • Carbon monoxide poisoning ± cyanide • Clostridalmyositis (gas gangrene) and necrotizing soft tissue infection • Crush 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

33. Recompression Treatment O2 Air breathing

34. Objectives • Review physics of compressed air diving • Complications during descent • Medical problems at depth • Complications during ascent • Prevention of complications • Prehospital care of dive injuries • Hyperbaric therapy for dive injuries

35. Questions?