Dear Ralph:
There are several problems with Doppler bubble detection and decompression.
[sp][1.] The early (1970s) use of Doppler bubble detection to monitor the ascent for a diver was unsuccessful. It was initially believed that bubbles would appear just prior to DCS. This was in accordance with the Haldane concept of DCS. In actuality it was found that many divers on US Navy tables demonstrated gas bubbles in the venous system and never got the bends. It became clear that venous bubbles and DCS were not related (ie, "silent bubbles"), and this type of deco monitor was not operationally feasible.
[sp][2.] The current idea of DCS is that bubbles that form in a
localized area of the body sre the cause. Circulating gas bubbles have little to do with the joint-pain process.
[sp][3.] The bubbles detected with the Doppler devices arise primarily in the muscle and adipose (= fat) tissues. These tissues are not responsible for joint-pain DCS. There is therefore a disconnect between the bubbles in muscles and those in tendon and ligaments (the latter probably are related to DCS).
[sp][4.] In recreational diving, the incidence of DCS is very low and likewise the Spencer-Johanson bubble grades are low, or zero (mostly). It is therefore difficult to titrated the biomarker when there is not biomarker. This is different from altitude decompression where the incidence of venous (Doppler) bubbles is appreciable.
[sp][5.] The divers who use oxygen in their decompression find that they are less lethargic and feel better. This is an actual (apparently) improvement and results in what would presumably be a better decompression. I can imagine that the bubble grades would change in these two situations (with and without more oxygen, or deep stops). This is by no means certain however, and I would be very curious, if someone were to actually test it (Doppler monitoring), what were the results.
[sp] This is a variety of information that I would not be able to obtain in my present work situation (at NASA), since we do not deal with scuba diving.
If I think of something else, I will add to the posting.
Dr Deco:doctor: