Very high altitude after diving

[gerryw]

Dr. Deco

Due to a change of job, it appears that I will soon be moving North........ to Peru.

I will be living in Lima which is at sea level and commuting weekly to a mine at 15,000 feet, passing above 16,000 on the way in. I am diving quite actively where I am now in northern Chile, 100 dives in 2002 and well on the way to that number this year. I know that I will be diving less in the future. Unfortunately. ;-0 I am now trying to determine just how much less.

Most information regarding reduced pressure seems to be about flying after diving. Since the cabin pressure in airliners tends to be maintained at about 8,000 feet, my situation will be considerably more extreme than flying and presumably will require a longer interval after diving.

Are there resources available that deal with very low atmospheric pressures after diving so that I can understand what restrictions I will have to set for myself? While I may try high altitude diving at some point, that would be in the future and I only anticipate diving at sea level for now. I am strictly a recreational diver and never exceed the NDLs on my conservative Cobra. (Which you state on another thread does not really matter...) I dive air right now, though nitrox may be available in Lima. I'll know when I get there.

I would generally be going up on Monday morning, therefore diving on Sunday is out as I can't imagine less than a 24 hour interval. What I need to know is if I should wait 48 or more hours, which knocks off Saturday and effectively kills diving most weekends.

Gerry

 

[Dr Deco]

Dear Gerry:

Dive/Travel Interval

I would hazard a guess that 24 hours would be sufficient. Taking six halftimes for essentially a complete reaction, 1/6 of 24 hours is a 240-minute compartment. Most divers will not do much loading in this compartment. Then there is the slow ascent to 16,000 feet at a rather slow drive (assuming this is up a mountain road and not on an airplane).

Others?

I would appreciate what others might think of this diving and ascending. I do not have any experience in this area, and dive/fly research does not cover such altitudes.

Dr Deco :doctor:

 

[MikeFerrara]

W have discussed this before on the board. BRW's book "Technical Diving in Depth" has some good information on calculating SI required to avoid reaching critical tensions in the leading compartment. I haven't tried any actual ascents to see if it really works, though.

 

[gerryw]

Thanks for the thoughts, Dr. Deco. I guess my situation is a bit unusual. I was not really expecting a lot of research on this subject since research on diving and regular flying does not seem to be very rigorous yet. And lots of people fly after diving. But if there were any existing research I figured you would know about it!

By the way, the roads are not all that slow in this part of Peru. Paved from Lima all the way up to where I am going, but very steep in some areas. It is still a slower ascent than in a plane as you point out. After thinking about this a bit, I realize that I will have about 45 hours of low altitude time if I dive on Saturday AMs. Which is quite long in terms of halftimes.

I understand your argument that 24 hours should be enough, but since many agencies recommend (or until recently recommended) 24 hours to fly, it seems logical that a more extreme altitude would require more time to maintain the same safety factor.

I will be going to Lima next week. No diving for a while but I will see if anyone has local experience in this. There is no lack of mountains in the area....

Mike, I have not found any discussions about higher-than-flying altitudes on the board. Quite a lot about flying in airplanes.

I will at some point pick up BRW's book, though I was hoping for the results of some actual tests on people as opposed to calculations that I might get wrong!

Gerry