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Dive Medicine and Hyperbaric Therapy

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Air bubbles forced into pulmonary microcirculation and through to left atrium, ... Pulmonary DCS (the chokes) causes (1) substernal discomfort, (2) non-productive ... – PowerPoint PPT presentation

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Title: Dive Medicine and Hyperbaric Therapy


1
Dive Medicine and Hyperbaric Therapy
  • Dr. Michael Feldman
  • Sunnybrook-Osler Centre for Prehospital Care

2
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

3
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

4
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
(No Transcript)
6
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)

7
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

8
...A word from our sponsor
Physics Resistance is Futile.
9
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
10
Henrys 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 Valsalva maneuver)
  • Suit squeeze
  • Dental barotrauma
  • Lung squeeze (breath-hold divers, gt30 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 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

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 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

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
  • 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

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
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