Residual nitrogen-based flying-after-diving rules.
Dear readers,
Happy Sunday, especially for those not working (like me)!
With more and more destinations opening and, or, relaxation of rules, I am pretty sure many of you are travelling or plan to. Ok the picture probably doesn't reflect he kind of plane you will board but hey, I am selling the dream here!
What do I want to discuss today?
Residual nitrogen-based flying-after-diving rules.
Please keep in mind to observe the minimum surface interval. In other words, don't fly right away after your last dive. It could be life threatening. Instead, do wait a minimum of 12h for a single day of no decompression dive or at least 18h in case of multi-day or repetitive no decompression dives.
I know many people debate this, and argue that different people have different reactions. Still, don't try your luck and play by the book please.
If the rules are too complicated to remember, take the simple approach: do wait 24h after your last dive before boarding a plane. Nothing is ever guaranteed in life, but this is a common practice backed by studies and experiments.
A bit of history
For those interested, these researches were primarily conducted by the U.S Navy and the U.S. Air Force, as well as by associations like the Undersea and Hyperbaric Medical Society (UHMS) or Divers Alert Network (DAN). All had different standards, the Navy having the most agressive one with a two-hour (only) surface interval time while the the Air Force recommended 24h. Where was the truth? Well, DAN recommended 12h. I am not sure it is very (or was very) reassuring to have up to 22h delta between the most conservative and the most agressive suggestion (so much for sience...).
So in 1991 DAN launched experiments (I am glad I didn't do it, imagine being the one experiencing unchartered territories, might not be your typical easy Sunday beach dive).
How? Well I am not a doc so I won't pretend to teach you anything for here is the idea: estimate the relationship between preflight surface interval and decompression illness (DCI). Simply, the tested interval (or waiting time if you prefer) was approved or rejected based on the number of DCI incident for that interval. As always in life, there is not perfect solution. So the acceptance- rejection dilemna took into consideration to allow for mild DCI but limit serious DCI.
DAN laid the foundation for current standards for recreational diving, and we thank them for that.
Disclaimer: I know we are not talking about financial products here but still, allow me an additional note. DNA guidelines certainly reduce the risk of decompression sickness, it dosn't remove it completely.
A cheat sheet
If you need a pocket card to remember that, take that image below. DAN put it on a table for us.
Image credit: DAN - Divers Alert Network (dan.org)
Sincerely yours.
The Diving Bear
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