Re: [[PSUBS-MAILIST] Undersea Habitats]

[Subscuba@aol.com]

John, 

I have written a number of programs that calculate decompression problems and 
I would not make the statement about 30 feet.

I believe that dates from the turn of the century when a 50% reduction in 
ambient pressure was considered "Bend Proof" (pressure at 33 feet is two 
atmospheres while the surface it is 1 atmosphere). This was based largely on 
tests made with goats (Dr. Haldane). Unfortunately ( or perhaps fortunately) 
humans are not goats or perhaps not far removed from goats. (I'm not too sure 
about some of the people I've met.)

The math models usually assume various tissue time constants which is a gross 
oversimplification of the human body. There does not appear to be a tissue 
that corresponds to a fast tissue such as the lungs as Haldane assumed. The 
best that can be said is that the models seem to fit what happens.

I found that a lot of "common knowledge" was/is based on opinion and not 
facts such as you become more susceptible as you age. Or that the Navy dive 
tables are based on a 5% incident rate.

Exhaustive studies have not been done except empirically by tech divers. Some 
pearl/sponge divers blow the hell out of the Navy dive tables and live to 
tell about it. The Navy dive tables also have errors in the Tables with very 
little testing performed for the various dive profiles, especially the 100 
foot for 25 minutes.

I do not claim absolute numbers as 30 feet as absolute criteria nor do I 
think absolute numbers exist. The best I've seen is based on statistical 
predictions for decompression sickness which suggest that any dive carries a 
risk of decompression sickness. It has been rumored that one of the test 
subjects Dr. Spencer used in his testing program for silent bubbles (1976) 
would experience the symptoms of decompression sickness when he took a 
commercial air flight.

Anyway, for what it's worth, the reason I have looked into the problem is 
that I have been a witness and more to several Decompression sickness 
incidents. I have also written about these incidents which I can send you, 
but I don't think they are pertinent to this website.

That's what neat about 1 ATM subs.

Have fun,

Ken Martindale

PS I've never been Bent, luck?