You may have heard of divers who fly less than 12-hours after diving with no negative impact and others that wait a longer period who end up with symptoms of DCI and wondered why this happens. Dr John Parker, a Diving physician and Senior Dive Medical Consultant for DAN, discusses this issue.
I can understand the frustration involved in instances of divers who ignore the guidelines for flying after diving and get away with it while others who are cautious and careful may get decompression sickness (DCS).
Why some individuals are more susceptible to DCS we do not know. There may be some genetic factors affecting susceptibility. However, individual susceptibility can also vary from day to day depending on factors such as exercise, hydration, alcohol, smoking and anxiety. The current state of health may also be a factor as a heightened immune response may react more readily to decompression bubbles and cause symptoms. This is one reason we encourage people not to dive if they feel unwell. A diving profile tolerated one day may result in DCS the following week. I cannot explain it all; all I can do is advise you to follow the guidelines and leave others to take their risks. DAN America has conducted extensive research on flying after diving and current recommendations are:
Divers within the No-Decompression Limits
Dives requiring Decompression Stops
There is little experimental or published evidence on which to base a recommendation for decompression dives. A pre-flight surface interval substantially longer than 18 hours appears prudent.
Adding to the above, DAN AP’s Founder and author of DCI: A Simple Guide, John Lippmann, comments further:
There is no magic and safe interval for flying after diving. The risk of DCS precipitated by flying reduces with time, and the longer the surface interval, the lower the risk. We generally encourage divers to wait 24 hours before flying after a dive.
If you have symptoms after diving and you are planning to fly (or drive to altitude), we suggest that you call a DAN-supported diving hotline and seek advice prior to doing so. Sometimes symptoms can worsen significantly during or after being at altitude.
It can often take a long time, and several flights, to get to some dive destinations, and in some cases more than 24 hours. Some divers are known to begin diving immediately when they arrive but does that put them at greater risk for decompression illness? DAN’s Medical Team addresses this issue:
Mild dehydration can occur on long flights, especially when travellers cross several time zones; alcohol consumption can also contribute to dehydration. Generally speaking, dehydration is thought to predispose a diver to decompression illness because the washout of inert gas (nitrogen, in diving) is less effective in a dehydrated individual.
If there were a relationship between diving after flying and DCI, we would expect to see a great deal of decompression illness on the very first day of diving; some data suggests that there are more accidents on the first day of a planned multiday dive trip.
In a study where 88 cases of DCI were reviewed from the Caribbean, 33 or 37.5 percent occurred on the first day. The remainder occurred on days two through seven. Given that there are thousands of tourist divers who fly to Caribbean and Pacific dive sites, these numbers are far too small to establish a cause and effect.
Although no one can insist upon a 24-hour waiting period after flying, such a conservative approach to diving after flying is a reasonable idea as it gives divers an opportunity to rehydrate, adjust to a new climate and time zone, and rest up after a long flight.
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