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Altitude gas expansion in flight — DIPIMC MCQ

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HardRetrieval and TransportAltitude gas expansion in flightDIPIMCDipIMC

A patient with a traumatic pneumothorax has had a finger thoracostomy and is being transferred by helicopter to a major trauma centre. During the ascent the aircraft climbs to several thousand feet and the patient becomes more breathless with rising airway pressures. What is the most appropriate explanation and action?

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Correct answer: C — Trapped gas expands at altitude, so recheck the chest decompression

As ambient pressure falls with altitude, trapped gas in body cavities expands in accordance with Boyle's law, so a pneumothorax can enlarge and a simple thoracostomy may need rechecking, with conversion to a chest drain or repeat decompression if tension features develop. Endotracheal tube cuffs and air-filled splints likewise expand and should be monitored. Rotary-wing aircraft are often unpressurised, and even modest climbs are significant in a patient with trapped air, so increasing oxygen does not address the underlying problem. Pearl: convert a thoracostomy to a formal chest drain and check cuff pressures before and during flight to pre-empt altitude-related expansion.

Reference: ATACC; Faculty of Pre-Hospital Care (RCSEd)