DCS9

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DCS9

  1. 1. Sgn Cdr John Duncan, RNZN Director of Naval Medicine Diving Medicine
  2. 2. Navy Hospital
  3. 3. Slark HBU
  4. 5. HMNZS MANAWANUI
  5. 6. Diving records <ul><li>7200 ft and submerged for two hours </li></ul><ul><li>2000ft and submerged for an hour </li></ul><ul><li>Free diving ~100m </li></ul><ul><li>No limits 214 Meters </li></ul>
  6. 7. Caisson Disease
  7. 9. Haldane <ul><li>1905-1907 Haldanes work </li></ul><ul><li>Five compartment model </li></ul><ul><li>2:1 Ratio </li></ul><ul><li>Research with goats </li></ul><ul><li>Refined on divers </li></ul><ul><li>Ironically a lot of divers today behave like goats </li></ul><ul><li>Still basis of tables today </li></ul>
  8. 10. Goat Picture
  9. 13. Diver Numbers
  10. 14. CAGE - cerebral arterial gas embolism <ul><li>Air trapped in lung may expand and burst into arterial system via pulmonary veins – goes to brain </li></ul><ul><li>Massive bubble load may cross to pulmonary veins through lungs – goes to brain </li></ul><ul><li>Presents with rapid onset neurological symptoms </li></ul><ul><li>Patients often recover, then deteriorate </li></ul>
  11. 15. Decompression illness <ul><li>Bubbles form in tissue/blood from dissolved N 2 on ascent if time / depth of dive was too great, and ascent is too fast </li></ul><ul><li>DCI can be avoided by very slow ascent (but this is sometimes too slow to be practical) </li></ul><ul><li>Bubbles damage vessels and tissue </li></ul><ul><li>Variable presentation - pain, weakness, feeling ‘off colour’, breathlessness </li></ul>
  12. 16. DECOMPRESSION ILLNESS - evolution of bubbles from dissolved nitrogen <ul><li>Air breathed at greater pressure during dive </li></ul><ul><li>Gas solubility increased at greater pressure </li></ul><ul><li>N 2 absorbed into blood and tissues </li></ul><ul><li>Amount of gas depends on time and depth </li></ul><ul><li>N 2 solubility declines during ascent (as pressure decreases) </li></ul><ul><li>Bubble formation - tissues and blood </li></ul>
  13. 17. RISK FACTORS FOR DCI <ul><ul><ul><li>Too deep / too long – exceed table limits </li></ul></ul></ul><ul><ul><ul><li>Rapid ascent </li></ul></ul></ul><ul><ul><ul><li>Omitted decompression </li></ul></ul></ul><ul><ul><ul><li>Repetitive diving (multiple ascents) </li></ul></ul></ul><ul><ul><ul><li>“ Bounce dives” </li></ul></ul></ul><ul><ul><ul><li>Flying after diving – no flying for 24 hours </li></ul></ul></ul><ul><ul><ul><li>Age </li></ul></ul></ul>
  14. 18. RISK FACTORS FOR DCI 2 <ul><ul><ul><li>Inter-current illness, cold, working hard, etc. </li></ul></ul></ul><ul><ul><ul><li>Panic </li></ul></ul></ul><ul><ul><ul><li>Gear Failure </li></ul></ul></ul><ul><ul><ul><li>Poor planing </li></ul></ul></ul>
  15. 19. Bubbles <ul><li>tissues </li></ul><ul><li>  </li></ul><ul><li> venous blood (some bubble formation) </li></ul><ul><li> </li></ul><ul><li> lungs </li></ul><ul><li> * </li></ul><ul><li>off-gas arteries  organs </li></ul>
  16. 20. Tissue bubbles <ul><li>Mechanical effects </li></ul><ul><ul><li>compression </li></ul></ul><ul><ul><li>stretch </li></ul></ul><ul><ul><ul><li>myelin sheaths, bone, spinal cord, tendon, etc </li></ul></ul></ul><ul><li>Biochemical </li></ul><ul><ul><li>activation of complement </li></ul></ul><ul><ul><li>coagulation </li></ul></ul><ul><ul><li>kinins </li></ul></ul>
  17. 21. Effects <ul><li>Reduced microcirculation </li></ul><ul><ul><li>ischaemia (haemorrhagic or thrombotic) </li></ul></ul><ul><ul><li>vessel permeability </li></ul></ul><ul><ul><li>oedema </li></ul></ul><ul><ul><li>inflammation </li></ul></ul>
  18. 22. DECOMPRESSION ILLNESS - presentation of disease <ul><ul><ul><li>Marked variation, from mild constitutional symptoms to paralysis </li></ul></ul></ul><ul><ul><ul><li>Most cases apparent within 24 hours </li></ul></ul></ul><ul><ul><ul><li>Only 50% have objective signs </li></ul></ul></ul><ul><ul><ul><li>Worst cases are early onset with progressive neurological symptoms </li></ul></ul></ul><ul><ul><ul><li>Diving may not reflect severity </li></ul></ul></ul><ul><ul><ul><li>Neurology may not “make sense” </li></ul></ul></ul>
  19. 23. Classification <ul><li>Decompression sickness </li></ul><ul><ul><li>Type I - musculoskeletal, skin, lymphatic, constitutional </li></ul></ul><ul><ul><li>Type II - neurological, cardiorespiratory, vestibular </li></ul></ul><ul><li>Arterial gas embolism </li></ul><ul><li>Barotrauma </li></ul><ul><ul><li>Little diagnostic or prognostic significance </li></ul></ul>
  20. 24. Current classification <ul><li>Decompression illness </li></ul><ul><ul><li>acute or chronic </li></ul></ul><ul><ul><li>static, progressive, relapsing, spontaneously resolving </li></ul></ul><ul><ul><li>organ system involved (cutaneous, cerebral, spinal, musculoskeletal, lymphatic, etc) </li></ul></ul><ul><ul><li>+/- barotrauma </li></ul></ul>
  21. 25. Differentiating between pathological processes <ul><li>Decompression illness - due to inert gas load and bubble evolution…. </li></ul><ul><li>Barotrauma </li></ul><ul><li>Other diving-related illness </li></ul>
  22. 26. <ul><li>Depth-time profile gives indication of inert gas load </li></ul><ul><li>Pattern of dive - no. and speed of ascents, etc </li></ul><ul><li>Time of onset of symptoms </li></ul><ul><li>Symptom evolution </li></ul><ul><li>Signs </li></ul>Making a diagnosis
  23. 27. Cerebral emboli - CAGE <ul><li>Usually rapid onset on surfacing </li></ul><ul><li>Loss of consciousness or fitting </li></ul><ul><li>Victims may drown </li></ul><ul><li>Spontaneous recovery of consciousness </li></ul><ul><li>Apparent resolution, then deterioration </li></ul>
  24. 28. Symptom frequency Symptoms after diving are common, DCI is not <ul><li>Pain 40% </li></ul><ul><li>Altered sensation 20% </li></ul><ul><li>Dizziness 8% </li></ul><ul><li>Fatigue, headache, weakness 5% </li></ul><ul><li>Nausea, SOB 3% </li></ul><ul><li>Altered LOC 2% </li></ul><ul><li>Rash < 1% </li></ul>
  25. 29. DECOMPRESSION ILLNESS classical vs typical patients <ul><li>THE ‘CLASSICAL’ </li></ul><ul><li>PATIENT </li></ul><ul><li>Exceeds time / depth </li></ul><ul><li>Rapid onset of pain </li></ul><ul><li>Followed soon after by weakness and sensory changes </li></ul><ul><li>Presents early </li></ul><ul><li>THE ‘TYPICAL’ </li></ul><ul><li>PATIENT </li></ul><ul><li>Borderline time / depth </li></ul><ul><li>Initially well </li></ul><ul><li>Later, migratory aches, feels “off colour” and tired </li></ul><ul><li>Seeks help several days after diving </li></ul>
  26. 30. DECOMPRESSION ILLNESS - presentation by system
  27. 31. Assessing a diver <ul><li>A, B, C and if conscious and talking – start oxygen @ 4L/minute, take blood pressure and pulse </li></ul><ul><li>RECORD EVERYTHING – TIME, etc </li></ul><ul><li>Dive profile – depth, time, gas, any events </li></ul><ul><li>When did they first notice symptoms? </li></ul><ul><li>What were they? </li></ul><ul><li>What has happened to the symptoms since? </li></ul><ul><li>How do they feel now? </li></ul><ul><li>When did they last pass urine? </li></ul>
  28. 32. DECOMPRESSION ILLNESS - evaluation in first aid <ul><li>BRIEF HISTORY BRIEF EXAMINATION </li></ul><ul><li>Depth(s) / time(s) Vital signs </li></ul><ul><li>Number of ascents Chest </li></ul><ul><li>Nature of ascents Neurological </li></ul><ul><li>Nature of dive </li></ul><ul><li>Symptoms </li></ul><ul><li>Temporal relation of </li></ul><ul><li>symptoms to dive </li></ul>
  29. 33. 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
  30. 34. D.E.S. service <ul><li>Available 24/7 </li></ul><ul><li>Call will be answered by Navy Hospital staff - get basic details </li></ul><ul><li>Give contact number </li></ul><ul><li>Experienced doctor & consultant on call </li></ul><ul><li>Response: </li></ul><ul><ul><li>advice on initial management </li></ul></ul><ul><ul><li>transfer immediately (St John coordinate) OR </li></ul></ul><ul><ul><li>assess at local hospital OR </li></ul></ul><ul><ul><li>review next day </li></ul></ul>
  31. 35. DECOMPRESSION ILLNESS - steps in DCI first aid <ul><li>ABCs </li></ul><ul><li>Position </li></ul><ul><li>Oxygen </li></ul><ul><li>Fluids </li></ul><ul><li>Evaluate </li></ul><ul><li>Contact D.E.S. </li></ul><ul><li>Evacuate </li></ul>
  32. 36. DECOMPRESSION ILLNESS - positioning in first aid <ul><li>CURRENT ADVICE </li></ul><ul><li>Horizontal </li></ul><ul><li>Recovery position if LOC is decreased </li></ul><ul><li>Previous advice was head down </li></ul><ul><li>THE CASE AGAINST </li></ul><ul><li>HEAD DOWN </li></ul><ul><li>Difficulty </li></ul><ul><li>Oral fluid administration </li></ul><ul><li>Increase ICP and cerebral oedema </li></ul><ul><li>Arterialisation of venous bubbles </li></ul>
  33. 37. DECOMPRESSION ILLNESS - oxygen in first aid
  34. 38. DECOMPRESSION ILLNESS - IV fluids in first aid
  35. 39. Adjunctive treatments <ul><li>Possible benefit: </li></ul><ul><ul><li>NSAIDs (oral, IM) </li></ul></ul><ul><ul><li>lignocaine (IV infusion) </li></ul></ul><ul><li>Of no benefit: </li></ul><ul><ul><li>heparin or other anticoagulants </li></ul></ul><ul><ul><li>steroids </li></ul></ul>
  36. 40. DECOMPRESSION ILLNESS - evacuation in first aid <ul><ul><ul><li>Not always necessary </li></ul></ul></ul><ul><ul><ul><li>Advice from D.E.S. is usually sought first </li></ul></ul></ul><ul><ul><ul><li>Minimise altitude – either road, or fixed wing at normal atmospheric pressure (1 ATA), or rotary (but <300m) </li></ul></ul></ul><ul><ul><ul><li>Maintain oxygen administration </li></ul></ul></ul><ul><ul><ul><li>Maintain horizontal posture in acute cases </li></ul></ul></ul><ul><ul><ul><li>Avoid pain relief </li></ul></ul></ul><ul><ul><ul><li>No entonox </li></ul></ul></ul>
  37. 41. Helicopter vs fixed wing <ul><li>HELICOPTER </li></ul><ul><li>Noisy </li></ul><ul><li>Poor access to patient </li></ul><ul><li>Unpressurised </li></ul><ul><li>Ideal for short coastal distances </li></ul><ul><li>Good for isolated areas, boats </li></ul><ul><li>FIXED WING </li></ul><ul><li>Quieter </li></ul><ul><li>Better access </li></ul><ul><li>May be pressurised </li></ul><ul><li>Ideal for long haul over high country </li></ul><ul><li>Limited if no strip </li></ul>
  38. 42. Summary: initial management <ul><li>CPR if necessary </li></ul><ul><li>Oxygen - 100% if possible (need rebreather) </li></ul><ul><li>Lie flat </li></ul><ul><li>Get advice </li></ul><ul><li>Rehydration (fluid balance) </li></ul><ul><ul><li>oral or IV crystalloid </li></ul></ul><ul><ul><li>1L stat, 1L 4-6 hrly </li></ul></ul><ul><li>Evacuate for recompression </li></ul><ul><li>NSAIDs if needed </li></ul>
  39. 43. Recompression treatment <ul><li>Recompress diver to depth </li></ul><ul><ul><li>can use oxygen or oxygen-helium </li></ul></ul><ul><ul><ul><li>bubble compression </li></ul></ul></ul><ul><ul><ul><li>increase diffusion gradient so gas leaves bubble </li></ul></ul></ul><ul><ul><ul><li>counter effects of pulmonary AV shunting </li></ul></ul></ul><ul><ul><ul><li>deliver high oxygen tensions to damaged tissue </li></ul></ul></ul>
  40. 44. <ul><li>Recompression therapy </li></ul><ul><li>18m </li></ul><ul><li>30min </li></ul><ul><li>9m </li></ul><ul><li>1hr </li></ul><ul><li>2hrs surface (0m) </li></ul><ul><li> = air ‘breaks’ to reduce oxygen toxicity </li></ul><ul><li>(and for convenience, comfort, etc) </li></ul>

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