SAQ 86 – Environmental Medicine – decompression illness

Question 1. decompression illness.

a. Historical features

• Large joint pain, often a single large joint.
• Vestibular symptoms: tinnitus, hearing loss, dizziness, or unsteady gait.
• Pulmonary symptoms: chest pain, dyspnoea, or cough.
• Headache, loss of consciousness, behavioural or mood change.
• High-risk dive profile: deep or long dive, rapid ascent, short surface interval, repeated dives.
• Prior decompression illness.

b. Examination findings

• Central neurological signs, including cerebellar signs, nystagmus, ataxia, or hearing loss.
• Peripheral neurological signs: patchy motor or sensory deficits at multiple sites.
• Balance disturbance, including abnormal sharpened Romberg testing.
• Severe joint pain with normal-appearing joints.
• Cyanosis, haemodynamic instability, or pruritic erythematous rash.

c. Investigations

• Decompression illness is primarily a clinical diagnosis.
• Investigations should not delay hyperbaric consultation or transfer when the diagnosis is likely.
• Investigations may help exclude alternatives, such as CT brain for another neurological diagnosis.
• CXR or Doppler may demonstrate gas emboli or microbubbles, but findings may be absent or nonspecific.

d-e. Consultation threshold and rationale

• Use a low threshold: discuss any suspected decompression illness with a hyperbaric specialist, even if symptoms appear mild.
• Symptoms and signs may be subtle but still indicate need for recompression.
• Specialist advice guides triage, transfer, and recompression decisions.
• Earlier treatment is associated with better outcomes, especially when started within about 12 hours.
• Benefit may still exist after delayed presentation.

f. Hyperbaric oxygen benefits

• Reduces bubble volume.
• Improves oxygen delivery to ischaemic tissue.
• May reduce intracranial pressure.
• Limits secondary inflammatory and reperfusion injury.
• May improve cerebral metabolism.