Some time ago, I wrote about the effect of flying on pneumothorax (PTX). It was more of a hypothetical treatise, discussing Boyle’s law and such. I also cited a practice guideline and another empiric guideline from the Aerospace Medical Association. But there was little, if any, real data to base recommendations on.
A recent study has tried to rectify this. They performed a prospective, observational study of 20 patients with traumatic pneumothorax. All were treated with either a chest tube (70%) or high flow oxygen therapy (30%) (they must not have read my many posts on the futility of this; see the links below). If a chest tube had been inserted, it had to have been removed for 4 to 48 hours before enrollment in this study, and the PTX had to be resolved to the satisfaction of the surgeon. This did not necessarily mean complete resolution.
Here are the factoids:
- A hyperbaric chamber was used to simulated the cabin altitudes of commercial jetliners
- 10 patients were taken up to 8400 feet, the typical cabin altitude when a jet flies at 40000 feet
- 10 patients were taken up to 12650 feet to compensate for the fact that the altitude of the medical center conducting the study was already 4500 feet (Murray, UT). This simulated an 8400 foot altitude increase for ground dwellers in Murray.
- Results were measured using portable chest x-ray (!??)
- PTX etiology was 90% blunt, 10% penetrating
- At 8400 feet, average PTX size doubled from 4.5mm to 10mm
- At 12650 feet, average PTX size nearly tripled from 3.2 to 8.7mm. Three of 4 patients without a baseline PTX developed one at this altitude.
- Some patients in each group required supplemental O2 to maintain normal oxygen saturation readings
Based on these results, the authors believe that patients who had a PTX might be able to fly sooner than 2 weeks. But there are many problems with this study. First, using a chest x-ray to monitor increases in size (or judge pre-flight size) is notoriously inaccurate. Next, the statistical methods and sample size are just not adequate. And finally, the fact that PTX size increases predicted by Boyle’s law and O2 sat changes occurred is very worrisome.
Bottom line: This study was a nice try, but not robust enough to change anything. Yes, there is little data to support the 2 week no-fly rule after pneumothorax. But the size increases of the PTX in this study were worrisome, particularly because they used a diagnostic test that notoriously underestimates their size. I recommend sticking with the current recommendations and constructing a much better study.
Reference: Cleared for takeoff: The effects of hypobaric conditions on traumatic pneumothoraces. J Trauma 77(5):729-733, 2014.