Diving Medicine

Sgn Cdr John Duncan, RNZN Director of Naval Medicine

Navy Hospital

Slark HBU

HMNZS MANAWANUI

Diving records

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

Caisson Disease

Haldane

• 1905-1907 Haldanes work •Five compartment model •2:1 Ratio •Research with goats •Refined on divers •Ironically a lot of divers today behave like goats •Still basis of tables today

Goat Picture

0 -5 -10 -15 -20 -25 -30 1 2

Dive Profile

3 4 5

Depth

6 7

Diver Numbers

Diver Numbers Slark Hyperbaric Unit

90 80 70 60 50 40 30 20 10 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Number

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

Decompression illness

• Bubbles form in tissue/blood from dissolved N 2 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

DECOMPRESSION ILLNESS - evolution of bubbles from dissolved nitrogen

 Air breathed at greater pressure during dive  Gas solubility increased at greater pressure  N 2  absorbed into blood and tissues Amount of gas depends on time and depth  N 2  solubility declines during ascent (as pressure decreases) Bubble formation - tissues and blood 16

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 17

RISK FACTORS FOR DCI 2

• Inter-current illness, cold, working hard, etc.

• Panic • Gear Failure • Poor planing

Bubbles

tissues  venous blood (some bubble formation)  lungs * off-gas arteries  organs

Tissue bubbles

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

Effects

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

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” 22

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

Current classification

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

Differentiating between pathological processes

• Decompression illness - due to inert gas load and bubble evolution….

• Barotrauma • Other diving-related illness

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

Cerebral emboli - CAGE

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

Symptom frequency

Symptoms after diving are common, DCI is not • Pain 40% • Altered sensation • Dizziness • Fatigue, headache, weakness • Nausea, SOB • Altered LOC • Rash 20% 8% 5% 3% 2% < 1%

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 29

DECOMPRESSION ILLNESS

-

presentation by system Constitutional Musculo Skeletal

Fatigue Malaise “Off colour” Pain - joints - limbs - girdles

Skin

Rash Itch

Heart / Lungs Neurological

“(Anything)” Cough Dyspnoea Chest pain Weakness Sensory change Bladder and bowel 30

Assessing a diver

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

DECOMPRESSION ILLNESS - evaluation in first aid BRIEF HISTORYBRIEF EXAMINATION

Depth(s) / time(s) Number of ascents Vital signs Chest Neurological Nature of ascents Nature of dive Symptoms Temporal relation of symptoms to dive 32

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 (09) 4458454

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

DECOMPRESSION ILLNESS - steps in DCI first aid

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

• Evacuate 35

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 36

DECOMPRESSION ILLNESS - oxygen in first aid

CURRENT ADVICE

 damaged valve; bag/mask/reservoir  Record time on / any time off / clinical effects

RATIONALE

 Promote N 2 outgassing  Promote bubble resolution  Oxygenate ischaemic tissue 37

DECOMPRESSION ILLNESS - IV fluids in first aid CURRENT ADVICE

 0.9% NaCl 1000 ml stat and 100-250 / hr  Titrate against output in long evacuations  Record fluid balance

RATIONALE

 Divers are usually dehydrated  DCI= a compromise of the microcirculation  DCI and dehydration are a bad combination  may need catheter 38

Adjunctive treatments

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

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 <300m) • Maintain oxygen administration • Maintain horizontal posture in acute cases • Avoid pain relief • No entonox 40

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

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

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

Recompression therapy 18m 30min 9m 1hr 2hrs surface (0m) •  = a ir ‘breaks’ to reduce oxygen toxicity (and for convenience, comfort, etc)