Diving Injuries

1. Diving Injuries Department of Diving and Hyperbaric Medicine Prince of Wales Hospital

2. Not All Diving Injuries Are Due to Decompression Illness Most diving injuries are not due to decompression illness There are many other causes of symptoms after diving: • Environmental • Sea sickness • Sunburn • Hypothermia • Near drowning • Disembarkation syndrome • Barotraumas • Middle ear • Sinuses • Pulmonary

3. Not All Diving Injuries Are Due to Decompression Illness • Gas toxicity • N2 narcosis • O2 toxicity • Gas contamination eg CO • Trauma • Envenomation • Non - diving related ie usual medical issues • ACS • Asthma • Anxiety • Malaria

4. Decompression Illness • Is due to bubble injury to the tissues • Bubbles may injure tissues by: • Obstruction • Disruption • Compression • Inflammation • There are two sources of bubbles: • Venous/tissue bubbles (=decompression sickness) • Arterial bubbles (=arterial gas embolus)

5. Pathophysiology of Decompression Sickness There are TWO prerequisites: • Need to breathe an inert gas under pressure eg N2, He, H2 • THEN need to return to a lesser pressure Increased absorption of inert gas occurs with: • Depth • Duration • Exercise • Cold Increased bubble formation occurs with: • Rapid reduction of depth/pressure • Exercise • Altitude • Heat Venous/tissue bubbles are often benign & filtered out by the lungs

6. Pathophysiology of Arterial Gas Embolus Due to air bubbles in the arterial circulation • Diving related: • Pulmonary barotrauma • Venous bubbles & PFO (or other left→right shunt) • Venous bubbles & overwhelm pulmonary filter • Non-diving related: • Invasive lines eg CVC, intracerebral arterial catheters • Anaesthesia/surgery eg cardiac surgery • Other Arterial bubbles are never benign Arterial bubbles are also buoyant, so float to the highest point =CNS when erect, elsewhere when not

7. Symptoms of Decompression Illness The symptoms of decompression illness are: • Non specific • Onset immediate-delayed • May be very minor to immediately life threatening • May be constant, or improve or worsen with time

8. Symptoms of Decompression Illness Systems involved: • Constitutional • Musculoskeletal • Neurological • Cardiorespiratory • Cutaneous • Lymphatic

9. Symptoms of Decompression Illness The possible symptoms include: • Constitutional • Fatigue • Headache • Nausea • Flu like illness • Musculoskeletal • Pain- arthralgia and myalgia • Weakness

10. Symptoms of Decompression Illness • Neurological • Peripheral including • Local weakness • Numbness, paresthesia • Central including • Visual change, diplopia • True vertigo • Paralysis including hemiplegia and paraplegia • Cardiorespiratory • The “chokes”, a PE like syndrome • Cutaneous • Lymphatic

11. Symptoms of Decompression Illness Clinical Pearl #1 To have decompression illness, you must have: • Been breathing an inert gas under pressure • Then return to a lesser pressure Clinical Pearl #2 Decompression illness symptoms MUST onset between leaving the bottom and 12-24 hours after leaving the water

12. Diagnosis of Decompression Illness • Diagnosis is made almost entirely on history and examination • There are no specific investigations • Further investigation at presentation only really required if patient critically ill, or to rule out other causes • History focusses especially on: • Past diving history • Diving profile & any missed decompression • Nature & time course of symptoms • Examination focusses especially on: • Musculoskeletal • ENT • Neurological • Sharpened Rombergs

13. Some Risk Factors for Decompression Illness • Multiple dives • Deeper dives >30m • Missed decompression • Altitude • Dehydration • Alcohol • Exertion • Fatigue

14. Treatment of Decompression Illness • Remove from water • Lie flat • 100% oxygen • Intravenous fluids • Early hyperbaric consultation THEN, once diagnosis confirmed/others excluded • Hyperbaric oxygen therapy • Non steroidal antiinflammatory • ??Lignocaine

15. Hyperbaric Treatment of Decompression Illness Hyperbaric oxygen treatment has two components: • Pressure to squash bubbles • High dose oxygen to: • Facilitate diffusion of inert gas (usually N2) out of the patient • Act as anti-inflammatory Treatment options include: • RN 62 or USN 6 • RN 61 • Comex • 14:90:20

16. Outcome of Treatment of Decompression Illness • Most patients require 2-5 daily hyperbaric oxygen treatments & many make a full recovery • The vast majority safely return to diving • Determinants of outcome include: • Depth of dive • Time to recompression • Severity of symptoms • Number of insults • 30% have some recurrence of symptoms

17. Other Hyperbaric Oxygen Emergency Indications • Acute carbon monoxide poisoning • Necrotising fasciitis/gas gangrene NB This is a surgical emergency, and should be referred direct to your local surgeons. They can come to us after initial debridement and antibiotics

18. Acute Carbon Monoxide Poisoning Clinical Pearls • Acute carbon monoxide poisoning can still be rapidly lethal • Not all exposures are intentional self harm • Usually a polyoverdose, so consider other toxins • Immediate 100%O2 is highly therapeutic • Whilst diagnosis is often made on COHb level, this is highly influenced by background exposure and time & O2 treatment since exposure • The goal of hyperbaric oxygen treatment is rarely to treat the acute poisoning, but to prevent delayed neuropsychiatric sequelae

19. Current Indications for Hyperbaric Oxygen Treatment of Acute CO Poisoning • Sustained LOC or • Hard neurological signs or • Cardiovascular compromise or • COHb level >30% or • Pregnant AND able to be safely compressed within 6-12 hours of exposure The goal is to pick the more severe poisonings, as they are the ones more prone to delayed neuropsychiatric sequelae