Posted by RaiderKarl on April 30, 2001 at 13:31:56:
In Reply to: Doppler Testing? posted by Steve on April 29, 2001 at 10:41:03:
Steve, you "see it mentioned more often" because PADI used it to determine its own 130 ft max recommended/required depth for recreational nondecompression diving, and the max NDLs at all depths within 130 ft. The other scuba agencies followed along in tandem very soon afterwards.
The Doppler Ultrasound Bubble Detector used by PADI and DSAT (Diving Science And Tech Corp.) identifies small bubble formation even below the U.S. Navy decompression limits. Therefore PADI reasoned within itself and with its insurance affiliates that no diving should occur beyond the levels where these bubbles are detected, even though there is no sign of DCS in the overwhelming majority of cases under these diving restraints.
130 feet is a fairly rigorous contraint, especially when you compare it with the popular European constraint of 150 feet on a similar basis, or the U.S. Navy / NOAA limit of 190 feet for 5 minutes.
We, the scientific and nonscientific world, still do not know exactly why, when, and how DCS is caused, and what if anything "small bubbles" has to do with it. Presumably the small bubbles may be the "seeds" upon which the bigger bubbles grow that are fairly universally believed to cause DCS.
And thats the current state of the science, and moreover the lawsuits and insurance claims, such that you see and hear "mentioned more often" about doppler now.
/s/ RaiderKarl
PADI D/M