Decompression sickness — DTM&H MCQ

Correct answer: C — Immediate recompression in a hyperbaric chamber with high-flow oxygen

The correct answer is C, immediate recompression in a hyperbaric chamber with high-flow oxygen. The stem describes decompression sickness (the bends) with type II (neurological) features: musculoskeletal pain, cutis marmorata (skin mottling), and paraesthesia occurring shortly after surfacing from a deep dive. This is caused by nitrogen bubbles forming in tissues and blood as ambient pressure falls faster than dissolved gas can be off-loaded; recompression physically reduces bubble volume and hyperbaric oxygen improves gas gradients for nitrogen elimination and tissue oxygenation. NHS England commissions hyperbaric oxygen therapy specifically for decompression illness, reflecting this as the definitive, guideline-endorsed treatment rather than an adjunct. Delay increases the risk of permanent neurological injury, so evacuation to the nearest chamber must not be deferred for symptom resolution on surface oxygen alone. Why the other options are wrong: E. High-flow oxygen and oral analgesia only: surface oxygen is correct first aid while arranging transfer but is inadequate definitive treatment for a case with neurological and dermal features; it does not reverse bubble formation. B. IV heparin and bed rest: anticoagulation has no established role in decompression sickness; bed rest alone does not eliminate nitrogen bubbles and risks progression of neurological injury. D. IV dexamethasone and bed rest: corticosteroids have no proven benefit in decompression sickness and are not part of recognised management; they do not address the underlying bubble pathology. A. Gradual decompression over 24 hours: this describes a slow staged ascent, the opposite of what is required; the emergency is treated with recompression to reduce bubble size, not further slow decompression. Key point: Any diver with neurological or dermal decompression sickness symptoms needs urgent transfer for hyperbaric recompression with 100 percent oxygen, not simply surface oxygen or supportive drug therapy.

Reference: NHS England, Clinical Commissioning Policy: Hyperbaric Oxygen Therapy for Decompression Illness/Gas Embolism, 2018, https://www.england.nhs.uk/wp-content/uploads/2018/07/hbot-for-decompression-illness-gas-embolism-v2.pdf