Dear Doctor Column, May 24, 2004

Scuba Safety: Diving and Flying

Question:

I'm going to a resort in Mexico for a week to scuba dive. I know you're supposed to wait several hours before you get on the plane after your last dive, but how long is a safe interval? The guys at my dive shop say 12 hours, but I've read it should be 24 hours.

Answer:

This has long been a subject of debate and really depends on what type of diving you have been doing. If you dive before you fly, you put yourself at increased risk of decompression sickness. Nitrogen still dissolved in your body at sea level could form bubbles as the airplane ascends: The more nitrogen in your body, the more likely this would happen. Even divers who meticulously adhered to their diving decompression schedules could be at risk for decompression sickness and other complications, if they go from deep sea to sea level to an airplane cabin (which may be at less than one atmosphere of pressure) within a very short span of time. The body simply cannot adjust to all those pressure changes that rapidly, especially if age, volume depletion, or other risk factors are present.

Twelve hours is accepted by many experts as a safe, minimum interval for someone who has made a single dive or one dive per day over several days. The real debate concerns what constitutes an appropriate time to fly for a diver who has made multiple, repetitive dives over several days, as is commonly done at many resorts and liveaboard dive boats.

Until there is hard scientific data to support a 12-hour or 24-hour decision, it may be best to advocate a "better safe than sorry" attitude. Advances, such as dive computers, slow ascents, and the 15-foot, 5-minute safety stop, also have helped eliminate chances of decompression sickness. Many resorts also do not schedule deep dives for guests in the 24 hours prior to their scheduled departure, for added safety.

Bottom line: Given a situation where you have control over the surface interval before flying after completing multiple dives, wait 24 hours. This decision provides the least amount of risk, however, the ultimate decision — and responsibility — is yours.

Additional resources for information are the Federal Aviation Administration, Office of Aerospace Medicine (www.faa.gov/passengers) and "International Travel and Health" (online edition), World Health Organization (www.who.int/ith).