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 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

Diver Numbers

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

16 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

17 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

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-gasarteries  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

22 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”

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

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 Making a diagnosis

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 20% Dizziness8% Fatigue, headache, weakness5% Nausea, SOB3% Altered LOC2% Rash< 1%

29 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

30 DECOMPRESSION ILLNESS - presentation by system

Assessing a diver A, B, C and if conscious and talking – start 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?

32 DECOMPRESSION ILLNESS - evaluation in first aid BRIEF HISTORYBRIEF EXAMINATION Depth(s) / time(s)Vital signs Number of ascentsChest Nature of ascentsNeurological Nature of dive Symptoms Temporal relation of symptoms to dive

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)

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

35 DECOMPRESSION ILLNESS - steps in DCI first aid ABCs Position Oxygen Fluids Evaluate Contact D.E.S. Evacuate

36 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

37 DECOMPRESSION ILLNESS - oxygen in first aid

38 DECOMPRESSION ILLNESS - IV fluids in first aid

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

40 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

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)  = air ‘breaks’ to reduce oxygen toxicity (and for convenience, comfort, etc)