Volume 28, Number 4 - Wilderness Medical Society

Flying after diving, however, increases decompression stress since
ambient pressure is reduced below that experienced by the nonflying
diver. A typical commercial aircraft cabin altitude of 8,000 ft
(2,438 m) provides a pressure of approximately 0.76 atmospheres
absolute (ATA). Consider a diver completing a dive to 66 ft (20
m; 3 ATA). Returning to the surface at sea level pressure involves
a three-fold pressure reduction (3.0:1.0) from the maximum
depth of the dive. An 8,000 ft cabin pressure would generate a
greater decompression stress because of the four-fold pressure
reduction (3.0:0.76). As an additional hazard, unexpected cabin
depressurization, while unlikely, would generate even greater
decompression stress on any fliers having dived recently.
Divers Alert Network (DAN) and Undersea and Hyperbaric
Medical Society (UHMS) held a workshop in 2002 to review
the available data addressing flying after diving (FAD) and
decompression stress. Consensus guidelines were produced. The
guidelines apply to flight at cabin altitudes of 2,000 to 8,000 ft
(610 to 2,438 m) and to divers who do not have symptoms of
decompression sickness (DCS). Altitude excursions to less than
2,000 ft are considered mild enough to not warrant inclusion
(providing some wiggle room for moderate post-dive travel,
generally ground-based or possibly short, low altitude interisland
flights). Any diver with symptoms should seek treatment
prior to flight. Symptoms may include pain in joints or muscles,
numbness, tingling, paralysis, or compromised senses.
The explanatory text of the guidelines stipulates that the
recommended preflight surface intervals do not guarantee
avoidance of DCS. It is important to appreciate that longer
surface intervals will reduce DCS risk further 1 .
6 WILDERNESS MEDICINE // Fall 2011