Flying after diving if computer shows all compartments cleared?

[NDonahue]

When I lived in Jordan and had to climb to 1600m each time when leaving Aqaba, I hacked together a model in Excel that converts my DC data to square tables and then applies the Navy ascent to altitude tables. For nitrox I just converted max depth of dive to equivalent air depth of the breathed gas. If I can find it and clean it up a bit I’ll post it here for anyone interested to check my math.

Attached is an updated model that applies dive computer data to NOAA no-deco air tables and the NOAA Ascent table to show you NOAA’s recommended surface interval before ascending to altitude (1k-10k). As one would expect, the model works best with as “square” a dive profile as possible. It is extremely conservative when a diver follows a “V” profile.

Per usual, this is for educational / discussion purposes only. You are responsible for your choices. When in doubt, wait 48 hours.

I’d appreciate thoughts on how this compares to other’s experiences.

 

[NothingClever]

A pilot shared with me he dives rich and shallow on his final dive when he has a compressed timeline before cockpit duty. Of course, the topography and sealife have a lot to do with making that final dive worthwhile.

I wouldn’t put too much faith in the tissue graphs - they’re just a theoretical indication. I would, however, listen to my ears at an extended SS.

 

[inquis]

Attached is an updated model that applies dive computer data to NOAA no-deco air tables

Minor nit: "bottom time" for the NOAA/Navy tables is from leaving the surface to leaving the bottom (i.e., including the descent).

A potentially very useful improvement would be to incorporate the dive site elevation. I have seen various threads in the past from folks wondering about wait time until they can drive over a mountain pass after diving.

(FWIW, you might lengthen the dive table. I can see people trying to put in 20 dives for their vacation trip, not understanding the relative unimportance of the earliest days.)

Overall, I'd say it's a very useful and easy to use tool, especially for multiple dives. Nicely done!

 

[Nick_Radov]

The first symptom of DCS is denial. The main reason for the flying after diving time limit is to give you time to admit to yourself that you're bent and need to go to the chamber instead of flying home. I very much doubt that divers are actually getting bent on commercial airline flights: more likely they were already bent when they boarded and the reduction in ambient pressure just made the symptoms that much worse.

 

[Duke Dive Medicine]

The first symptom of DCS is denial. The main reason for the flying after diving time limit is to give you time to admit to yourself that you're bent and need to go to the chamber instead of flying home. I very much doubt that divers are actually getting bent on commercial airline flights: more likely they were already bent when they boarded and the reduction in ambient pressure just made the symptoms that much worse.

Though the DAN page linked below does call out that it's more common for existing DCS symptoms to get worse in flight than for asymptomatic divers to develop DCS symptoms, it's not unheard of. Also including @Dr Simon Mitchell 's article from 2024 (see risk factors for decompression sickness).

Flying After Diving

Pressure changes while flying after diving increase the risk of decompression sickness. Find out what you can do to help lower your likelihood of DCS.

dan.org

Decompression illness: a comprehensive overview - PMC

Decompression illness is a collective term for two maladies (decompression sickness [DCS] and arterial gas embolism [AGE]) that may arise during or after surfacing from compressed gas diving. Bubbles are the presumed primary vector of injury in both ...

pmc.ncbi.nlm.nih.gov

Best regards,
DDM

 

[boulderjohn]

Have you seen the 2 Cialoni studies?

The maddening thing about these studies is that after testing the individuals regularly while they were diving, they waited 24 hours to do the testing before flying. they found all of them to be bubble free at 24 hours. Why didn't they test them at the 18 hour mark, which is when DAN Americas usually says it is safe to fly? Is it possible they were already bubble-free at that point?

 

[Nick_Radov]

Though the DAN page linked below does call out that it's more common for existing DCS symptoms to get worse in flight than for asymptomatic divers to develop DCS symptoms, it's not unheard of.

Perhaps so, but my assertion is that almost all of those "asymptomatic divers" who developed DCS during a flight were actually ignoring minor symptoms prior to flying — or lying about them. I have no real proof of this, but I think that's generally what's going on based on anecdotal stories from other divers. Obviously it's impossible to study this in any definitive way.

 

[Duke Dive Medicine]

Perhaps so, but my assertion is that almost all of those "asymptomatic divers" who developed DCS during a flight were actually ignoring minor symptoms prior to flying — or lying about them. I have no real proof of this, but I think that's generally what's going on based on anecdotal stories from other divers. Obviously it's impossible to study this in any definitive way.

There is a mechanism of injury for initial symptom presentation during an ascent to altitude so it's reasonable to conclude that that does happen, though as you said the actual incidence would be hard to study. Of course the treatment would be the same regardless so this is moot except for the lesson of following established FAD guidelines and being mindful of symptoms of DCS.

Best regards,
DDM

 

[Altamira]

Being an old man and retired military and airline pilot, I am continually astounded there are apparently so many divers that are continually searching for that "study" that supports their willingness to risk DCS because of "get home-itis." From my perspective, a possible chamber ride or worse, is never going to be worth the cost of an extra night in a hotel and a nice relaxing dinner.

 

[inquis]

It is extremely conservative when a diver follows a “V” profile.

Just noticed that longer dives yield a "Danger" group identifier. While that's unsurprising when pretending a multi-level dive occurred at max depth, the estimated flight time seems to ignore that dive (and is dangerously early). In such cases, it's probably best to punt and just return 18 hours (DAN's repetitive dive guideline).