Flying after diving if computer shows all compartments cleared?

[inquis]

?? Were not these chamber tests done before SurfGF was invented?

Yes, but I'd say calling them chamber tests isn't quite right. The dives were real, [Edit: I checked again, and they were chamber dives. Thanks for the ping, @tursiops. I mistakenly confused the DSAT NDL experiments with the Duke study.] and the "flight" was conducted in a chamber to reduce the ambient pressure to about 0.75 atm (equivalent to 8k ft).

The surfGF values I gave come from running the dive & surface profiles through a planner (Subsurface). ETA: just another way to look at their results through a more current lens.

 

[dmaziuk]

On a normal flight you are pressurized to about 2400m above sea level. Thats about 75% of the pressure at sea level. In this regime there is litte experience to model. You need to offgas to be safe at this pressure (about 0.75 bar), which can be mathematically calculated.

"Can be": yes. However since our decompression models are designed for uncompressible (for our purposes) water, and air is compressible, our models don't work for this. There's math for high altitude pilots and astronauts, all I know about it is it's where bubbles came from.

I assume you can marry them to ZH-L16 and develop a model for diving in the water at altitude X and then ascending/descending to altitude Y in the air... but then you'll have to test it on goats and humans and that's pretty much not happening.

 

[Centrals]

24hrs(multi non decompression dives over multi days) regardless what my three different brands and algorithms dive computers indicated. Planned the last dive accordingly.
Scuba diving is only a recreational sport for me.

 

[justinthedeeps]

Takeoffs can be somewhat rapid--one to two minutes?--plus we are stuck in seats with potentially poor circulation while our ears pop like mad, if even only to a ~2000 metres apparent altitude (80% of surface pressure?)

We *could* play around with this like it's just "another deco stop," as I'm sure most tech divers have, but apparently that's not failsafe.

Have also wondered if driving over a pass is the same as flying; and this may too depend on ascent rate, circulation, duration at reduced pressure etc?

Another take:

Can we calculate no-fly-times? – The Theoretical Diver

thetheoreticaldiver.org

 

[Alekseolsen]

OSTC already have a "No fly time" on their computers, calcluated with a flight as 0.6 Bar(A)

I guess nobody know the validity, but they have at least had the function for quite some years!

 

[Edward3c]

Have also wondered if driving over a pass is the same as flying; and this may too depend on ascent rate, circulation, duration at reduced pressure etc?

The training for using the BSAC 88 Altitude Crossover Table covers both driving to/from hight and flying.

 

[inquis]

Have also wondered if driving over a pass is the same as flying; and this may too depend on ascent rate,

Yes, because ambient pressure is reduced. I don't consider the rate to be an issue -- even in an airplane -- as it's well below the pressure equivalent of 10 msw/min or 30 fsw/min. Granted, there is additional time for off-gassing during a slow ascent (as when driving), but that's a race condition that could easily go wrong. The biggest potential difference when driving is you often don't ascend 8000 ft higher than the dive site.

For the curious, the US Navy Ascent to Altitude table is the best source I know of for a dive-specific guidance. Be aware that it may be shorter or longer than DAN's guidance, but it's on you to compute it correctly. (FYI: nitrox and altitude complicate the calculations.)

 

[inquis]

Another take:

Can we calculate no-fly-times? – The Theoretical Diver

thetheoreticaldiver.org

The Duke study negates this argument, as people were still getting bent with a surfGF(8k) of a mere 20% -- far below what we believe to be safe enough when exciting the water. There is clearly something else at play. My opinion is it's due to the asymptomatic bubbling that we now know is very common and the expansion thereof with the post-dive ascent.

 

[lowwall]

The Duke study negates this argument, as people were still getting bent with a surfGF(8k) of a mere 20% -- far below what we believe to be safe enough when exciting the water. There is clearly something else at play. My opinion is it's due to the asymptomatic bubbling that we now know is very common and the expansion thereof with the post-dive ascent.

Have you seen the 2 Cialoni studies? They each examined a group of vacationing divers for bubbles after every dive for a week and on the flight home. Both studies found that there's a personal susceptibility to post dive bubbling. Most divers had no detectable bubbles after dives or on the flight. But about a quarter of the divers had bubbles after every dive. About half of the bubbling group also developed bubbles during the flight.

For the second study (2015), they advised the 2 divers with the highest post-dive bubble scores to skip the last dive, which left a 36 hour gap instead of 24 for all the other dives. These 2 did not bubble during the flight.

They recorded everything about the dives and divers. The only physical attribute that was correlated with bubbling is age. Older divers were more likely to exhibit bubbles. But bubblers did appear across the age spectrum. Dive profiles did not matter, but all dives were within no deco limits and all divers followed the same ascent rate (between 9 and 18 mpm aka 30 and 60 fpm) and safety stop (5 minutes at 5m) protocols.

I should note that none of the subjects were diagnosed with DCS at any time during the studies.

 

[NDonahue]

the US Navy Ascent to Altitude table is the best source I know of for a dive-specific guidance. Be aware that it may be shorter or longer than DAN's guidance, but it's on you to compute it correctly. (FYI: nitrox and altitude complicate the calculations.)

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.