Shallowest case of DCS?

[bluebanded goby]

Forgive me if this has been addressed elsewhere here, but I wasn't sure what search terminology to use to try to find it.

Is there a clearcut answer to the question: What is the shallowest depth at which a diver has ever experienced a documented case of DCS? I'd think it would be difficult to answer, because the mildest forms of DCS are so subtle that they might be glossed over.

I'd be curious about any responses, though, as the other day I got into a conversation with another diver on whether or not there was a depth or shallowness at which one is essentially absolutely safe from DCS. From what I've read I would think that you can never categorically say that any depth however shallow is absolutely 100% safe -- although certainly as you get shallower the risk gets to be pretty negligible. Thanks for any input on this!

 

[Dr Deco]

Dear Goby:


The shallowest depth depends on time at depth since gas loading is dependent on gas loading time (bottom time). When one is diving on a scuba bottle, this time is limited only at deep depths.

At shallow depths, more and more time is needed to achieve a good gas load. If you are a deep-sea diver with a surface supply (hose), you could stay at a shallow depth for quite a few hours since the gas supply is unlimited. You endurance is not, however. For long exposures, it necessary that one be in an underwater habitat or a hyperbaric chamber in a laboratory.

It appears that the shallowest depth from which one can ascend and still get the bends is about 25 feet. That is after an exposure of 48 hours.
[sp](Eckenhoff RG, Osborne SF, Parker JW, Bondi KR. Direct ascent from shallow air saturation exposures. Undersea Biomed Res 1986 Sep;13(3):305-16;
[sp]Ikeda T, Okamoto Y, Hashimoto A. Bubble formation and decompression sickness on direct ascent from shallow air saturation diving. Aviat Space Environ Med 1993 Feb;64(2):121-5) Doppler bubble have been found from shallower exposures.

The problem is true that as DCS becomes milder and milder, it passes completely into the “subclinical” range. This is then the realm of Doppler Bubbles. The minimum is probably determined by the largest microbubbles (“seeds” or micronuclei) that are present in large numbers.

One must always remember that pulmonary overpressure accidents can occur with very small pressure overloads to the lungs. The record is about 4 feet by children playing with an inverted tub in a swimming pool. This is a form of decompression sickness, although it is not “the bends.”

Never hold you breath – no matter how shallow. :nono:

Dr Deco