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Flying After Diving
by DAN Medical Team on March 1st, 2016

​I am a dive instructor in Venezuela. First, after making multiday repetitive dives, is an extended surface interval beyond 12 hours before flight considered enough? Second, driving to altitude after diving is one of our peak topics. Since our closest dive training site is a bay surrounded by mountains, after diving we must drive through a mountain pass nearly 1,000 feet / 305 meters above sea level, and then to Caracas, nearly 3,300 feet /1000 meters above sea level. Waiting 12 hours after recreational or training dive activities is not the local practice and, as far as I know, there have not been any reports of decompression sickness (DCS). Is our practice safe?
Revised Flying After Diving Guidelines for Recreational Diving - May 2002

The following guidelines are the consensus of attendees at the 2002 Flying After Diving Workshop. They apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) for divers who do not have symptoms of decompression sickness (DCS). The recommended preflight surface intervals do not guarantee avoidance of DCS. Longer surface intervals will reduce DCS risk further.
  • For a single no-decompression dive, a minimum preflight surface interval of 12 hours is suggested.
  • For multiple dives per day or multiple days of diving, a minimum preflight surface interval of 18 hours is suggested.
  • For dives requiring decompression stops, there is little evidence on which to base a recommendation and a preflight surface interval substantially longer than 18 hours appears prudent.

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Brian Fuller - March 26th, 2016 at 2:52 AM
I have always wondered about driving to altitude after diving as I live in St Helena, I will say in town for an hour or so before going in the country were I live.

R mccrory - March 27th, 2016 at 6:47 AM
We live at 1550 meters and after diving at sea level drive home with no effects.
DAN Medical Team - March 29th, 2016 at 4:23 AM
Thank you for these comments. We truly appreciate our members taking the time to respond, and allowing us to weigh in on the conversation!

The difficulty with DCS probability calculations in terms of flying after diving is that there are so many variables to consider: In addition to the actual dive profiles, and the corresponding residual nitrogen levels prior to making an excursion to altitude, there are many additional inter- and intra-individual variables as well - many of which are largely unquantified. For example, there is very little data on the effect of the rate of ascent to altitude on DCS probability - which may actually be quite relevant when traveling to altitude by car or by aircraft respectively.

For many reasons - many of them being either practically or economically motivated - flying and diving remains subject to controversy. Anthony Almon addresses this in his DAN article: Importantly, however, he describes a dramatic increase in the incidence of so-called "ambiguous" DCS symptoms when the intervals become less than 4 hours. In his words: "The correlation between the percentage of Ambiguous DCS and the surface interval was statistically significant, suggesting that the ambiguous symptoms were a mild form of DCS. At a three-hour surface interval, for example, there was a 10 percent estimated risk of Definite DCS and nearly a 20 percent estimated risk of Ambiguous DCS. The observed DCS percentage at six and nine hours does not follow the estimated trend due to the low number of studies that were conducted. You could decide to wait for 12 hours before your flight, and have an estimated 1 percent risk of Definite DCS and approximately 2 percent risk of Ambiguous DCS. If you want to keep your level of risk at zero, then don't dive or don't fly. Every time you dive, you are subjecting yourself to a risk of DCS. No tables guarantee absolute safety ."

Therefore, we have to be careful about appraising DCS risk with flying after diving. It is so easy to fall into the old "why wear a seat belt" trap: When you drive without a seat belt, and you don't die or get injured as a result, there is a tendency to think it might be safe to do so. However, in truth, you have neither proven that seat belts are unnecessary, nor that driving without them is safe. The true picture of risk only appears when viewed in the light of a larger sampling of the driving population. Unfortunately, this reality may remain invisible until the individual becomes a statistic themselves.
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