Dive Medicine and Hyperbaric Therapy

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Dive Medicine and Hyperbaric Therapy

• Dr. Michael Feldman
• Sunnybrook-Osler Centre for Prehospital Care

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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

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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

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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?

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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)

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Compressed air diving

• Mid-1800s 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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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
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Henrys Law
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Ascent Dissolved gas comesout of solution
andis exhaled
Descent Increased pressure increases
dissolvedgas
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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

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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 Valsalva maneuver)
• Suit squeeze
• Dental barotrauma
• Lung squeeze (breath-hold divers, gt30 m depth)

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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

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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

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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

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Lung Squeeze

• Rare complication in breath hold diving
• No limits diving mens world record 172 m
  womens 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

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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

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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

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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

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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

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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

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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

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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

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Cerebral Arterial Gas Embolism
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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

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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

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Prevention of Decompression Sickness

• Limit time spent at depth
• Slow and staged ascents (decompression stops) so
  that bodys 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

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USN Navy Dive Table
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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

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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

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HBOT - Indications

• Air or gas embolism
• Carbon monoxide poisoning cyanide
• Clostridal myositis (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

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Recompression Treatment
O2
Air breathing
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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

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Questions?