Computer Behavior - Diving after Flying

[Papa Steve]

I have a Zeagle N2ition. It stays on all the time. After we landed for our vacation last week and unpacked our gear I noticed my computer showed I had some residual nitrogen time showing. (I had not been diving for several weeks). I pulled out the manual and this is what I found . . .

Status: Although you are not diving, the computer goes into time mode and desaturation time is displayed.

Cause: This is caused by a change in altitude rank. When there has been a change in air pressure, the computer automatically calculates residual nitrogen. You should use this information in your diving plan.

I found that last sentence to be an interesting one. It would lead one to believe that flying before diving could impact your diving.

The residual nitrogen was pretty minimal but I found the discovery interesting none the less.

Thoughts and opinions????

 

[kadleck]

Interesting! I guess conservatism is a good thing anyway. I looked up what DAN has to say. It's more to do with the dehydration effects of flying, though DCI is mentioned (and pretty much dismissed). This was in the Q&A, in response to a Diving after Flying question:

Mild dehydration can occur on long flights, especially when travelers 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 -- indeed, some data suggests that there are more accidents on the first day of a planned multiday dive trip. Of the 88 cases reviewed from the Caribbean for 1994, 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 -- it gives divers an opportunity to rehydrate, adjust to a new climate and time zone, and rest up after a long flight.

 

[salth2owannabe]

This computer must automatically adjust for altitude dives and displays a residual nitrogen even prior to the dive, I guess just displaying that it has gone into a more conservative mode prior to the dive. The change in elavation during the flight makes the computer assume an altitude dive. I would think that after a short period of time it would revert back to a sea level dive.

I live in Idaho, but at a very low elavation, and many dives out here are affected by altitude even if your dive location isn't. We have a number of passes to drive over before or after the dive that may get to 6k or 8k feet or higher.

 

[don Francisco]

I hate psychoanalyzing computers, but just a guess.

It might have begun showing residual nitrogen when your plane gained altitude, and after descent the pressure wasn't great enough for dive mode, so it's still showing the desat time.

 

[Mr Carcharodon]

I have a Zeagle N2ition. It stays on all the time. After we landed for our vacation last week and unpacked our gear I noticed my computer showed I had some residual nitrogen time showing. (I had not been diving for several weeks). I pulled out the manual and this is what I found . . .

Status: Although you are not diving, the computer goes into time mode and desaturation time is displayed.

Cause: This is caused by a change in altitude rank. When there has been a change in air pressure, the computer automatically calculates residual nitrogen. You should use this information in your diving plan.

I found that last sentence to be an interesting one. It would lead one to believe that flying before diving could impact your diving.

The residual nitrogen was pretty minimal but I found the discovery interesting none the less.

Thoughts and opinions????

So did you fly to a higher altitude than your home? It would seem if you travel to altitude you would have residual nitrogen. I suppose if you flew from a sea level location to an other sea level location you would actually desaturate some during the flight. So you could actually start out with negative nitrogen time, or a credit if you will.

 

[SkipperJohn]

If there are some affects of flying before diving, your computer would probably be wrong anyway unless you had it in your carry-on. The luggage compartments of an aircraft are not pressurized. The passenger compartments are. So a computer stored with your luggage would be adjusting RN for a stow-away in the luggage compartment... I guess.

 

[kadleck]

The luggage compartments of an aircraft are not pressurized.

Not true! At least for all scheduled passenger airliners. The luggage compartments are pressurised just the same as the passenger cabin (equiv of 5000 to 8000 ft altitude, regardless of actual altitude), though they may not be climate controlled in the same way (quite often, the luggage area is cooler). Think about it - do you think they would be able to transport horses, dogs, and other animals (a very frequent cargo) if they did not pressurise the whole plane? Anyway, it would be a lot more complex, and probably even dangerously stressful on the airframe, to have two areas of the same aluminium tube (apologies for British spellings!) at different pressures.

 

[anzac65]

Not true! At least for all scheduled passenger airliners. The luggage compartments are pressurised just the same as the passenger cabin (equiv of 5000 to 8000 ft altitude, regardless of actual altitude), though they may not be climate controlled in the same way (quite often, the luggage area is cooler). Think about it - do you think they would be able to transport horses, dogs, and other animals (a very frequent cargo) if they did not pressurise the whole plane? Anyway, it would be a lot more complex, and probably even dangerously stressful on the airframe, to have two areas of the same aluminium tube (apologies for British spellings!) at different pressures.

Correct Mr Kadleck. And please don't apologise for using the Queen's english.

 

[Roko]

I've got the same computer, and I notice that it occasionally has a desat time when I'm not diving as well, probably from changing air pressure. I haven't been flying with it yet. Gotta love living and diving at altitude.

 

[SkipperJohn]

Not true! At least for all scheduled passenger airliners. The luggage compartments are pressurised just the same as the passenger cabin (equiv of 5000 to 8000 ft altitude, regardless of actual altitude), though they may not be climate controlled in the same way (quite often, the luggage area is cooler). Think about it - do you think they would be able to transport horses, dogs, and other animals (a very frequent cargo) if they did not pressurise the whole plane? Anyway, it would be a lot more complex, and probably even dangerously stressful on the airframe, to have two areas of the same aluminium tube (apologies for British spellings!) at different pressures.

good point. I myself have transported my dog a few times and the only concern was temperature. I learned something today.