Gas laws dictate the relationship between pressure and volume. As pressure decreases, the volume of a gas increases. If that volume of gas is a pneumothorax … the Aerospace Medical Association and the British Thoracic Society feel such hypobaric conditions, e.g., commercial air travel, are absolutely contraindicated.
But, does the small difference in atmospheric pressure – ~550mmHg versus 760mmHg – truly induce clinically important changes, such as tension physiology?
These clinicians in Salt Lake City enrolled patients with recently-treated traumatic or iatrogenic pneumothorax and subjected them to 2-hours of simulated air travel using a hyperbaric and hypobaric chamber. Twenty patients were included, 14 of whom received tube thoracostomy for their pneumothorax, with 11 still having residual pneumothorax visible on chest x-ray. Two types of simulated flights were performed – an initial 554mmHg phase intended to simulate aircraft cabin pressure, and a second phase using 471 mmHg, intended to compensate for the low baseline barometric pressure of 645 mmHg present in Murray, UT.
Did the volume of pneumothoracies increase as atmospheric pressure decreased? Yes. Did lungs explode? No. Did patients require emergency needle decompression? No. Did patients have any change in vital signs? No. And, all pneumothoracies returned to their baseline size following return to baseline atmospheric pressure.
Is this durable, generalizable, slam-dunk data regarding prospective guidance for air travel following small pneumothoracies? No. But, it’s a lovely bit of dogmalysis demonstrating an unnecessarily absolutist approach certainly is inappropriate, and doesn’t accurately describe the true individualized risks.
“Cleared for takeoff: The effects of hypobaric conditions on traumatic pneumothoraces”