Dear Scuba-Alan and Readers:
This is an interesting story and, when I web the description on the website, it was not evident that anything had been out of the ordinary. Your comment about weakness does indeed suggest neurological involvement. A paper publish in 1985 indicated that about one half of the divers experiencing CNS problems did so in the absence of any particularly difficult dives.
[Dick AP, Massey EW. Neurologic presentation of decompression sickness and air embolism in sport divers. Neurology 1985 May;35(5):667-71].
It is the Haldane concept of decompression sickness, with its
critical supersaturation limit that produces this almost metaphysical concept. Decompression sickness requires the presence of two factors. These are:
- [1.] An amount of dissolved gas in excess of what can be held in solution, at equilibrium, at that pressure, and
[2.] The presence of minute gas bubbles that can grow when the supersaturation exceeds the Laplace pressure (= contracting pressure resulting from surface tension).
If either is missing, growth of a decompression gas phase is not possible. The gas phase cannot form
de novo (= from nothing) from supersaturation alone unless it is hundreds of atmospheres. In fact, no one has been able to really test the tensile strength of water because of impurities present in the liquids. The theoretical limit of water, predicted by Fisher in 1948, is about 1300 atmospheres
(Fisher, J.C. (1948). The tensile strength of liquids. J. Appl. Phys. 19, 1062 - 1067.)
When some one gets the bends, they had too much gas in the tissues in addition to too many micronuclei. The tables and deco meters will only tell the former. Each diver must protect himself or herself against the latter. This is done by the avoidance of heavy musculoskeletal exercise.
In addition, there is the problem of arterialization of venous gas bubbles. This can result from a reversal of the left to right gradient in the atria of the heart. The most common way is by increasing the right atrial preload secondary to rebound flow. Ugh! That means, one performs a Valsalva-like maneuver (a true Valsalva maneuver, coughing, holding the breathe while climbing a ladder and then releasing it, etc.)
Without actually being present, I could not say what caused this undeserved hit. Suffice it to say that it was not engendered by the wrath of the gods on Mount Olympus. A physiological answer surely is at the basis. I wish that a more complete answer were possible.
In short, yes. You can do all the right deco procedures and still acquire decompression sickness.
Dr Deco:doctor:
, but seriousely- the fact that he had a chamber ride, dosent nessaserily mean he had a DCS (it means it was suspected he had it). If you can get any more details about the incident I would really apreciate it.
