Sgn Cdr John Duncan, RNZN

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Diving Medicine

• Sgn Cdr John Duncan, RNZN
• Director of Naval Medicine

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Navy Hospital
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Slark HBU
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HMNZS MANAWANUI
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Diving records

• 7200 ft and submerged for two hours
• 2000ft and submerged for an hour
• Free diving 100m
• No limits 214 Meters

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Caisson Disease
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Haldane

• 1905-1907 Haldanes work

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

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Goat Picture
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Diver Numbers
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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

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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

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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

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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

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RISK FACTORS FOR DCI 2

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

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Bubbles

• tissues
• ?
• venous blood (some bubble
  formation)
• ?
• lungs
• off-gas arteries ? organs

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Tissue bubbles

• Mechanical effects
• compression
• stretch
• myelin sheaths, bone, spinal cord, tendon, etc
• Biochemical
• activation of complement
• coagulation
• kinins

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Effects

• Reduced microcirculation
• ischaemia (haemorrhagic or thrombotic)
• vessel permeability
• oedema
• inflammation

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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

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Classification

• Decompression sickness
• Type I - musculoskeletal, skin, lymphatic,
  constitutional
• Type II - neurological, cardiorespiratory,
  vestibular
• Arterial gas embolism
• Barotrauma
• Little diagnostic or prognostic significance

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Current classification

• Decompression illness
• acute or chronic
• static, progressive, relapsing, spontaneously
  resolving
• organ system involved (cutaneous, cerebral,
  spinal, musculoskeletal, lymphatic, etc)
• /- barotrauma

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Differentiating between pathological processes

• Decompression illness - due to inert gas load and
  bubble evolution.
• Barotrauma
• Other diving-related illness

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Making a diagnosis

• 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

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Cerebral emboli - CAGE

• Usually rapid onset on surfacing
• Loss of consciousness or fitting
• Victims may drown
• Spontaneous recovery of consciousness
• Apparent resolution, then deterioration

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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 lt 1

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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

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DECOMPRESSION ILLNESS - presentation by system
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Assessing a diver

• A, B, C and if conscious and talking start
  oxygen _at_ 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?

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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

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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 [phone]

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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

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DECOMPRESSION ILLNESS - steps in DCI first aid

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

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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

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DECOMPRESSION ILLNESS - oxygen in first aid
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DECOMPRESSION ILLNESS - IV fluids in first aid
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Adjunctive treatments

• Possible benefit
• NSAIDs (oral, IM)
• lignocaine (IV infusion)
• Of no benefit
• heparin or other anticoagulants
• steroids

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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 lt300m)
• Maintain oxygen administration
• Maintain horizontal posture in acute cases
• Avoid pain relief
• No entonox

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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

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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

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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

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• Recompression therapy
• 18m
• 30min
• 
  9m
• 1hr
  
• 2hrs
  surface (0m)
• ? air breaks to reduce oxygen toxicity
• (and for convenience, comfort, etc)