Trimble, a journalist, makes HBO seem like the most miraculous remedy -- for cancer, heart attack, burns, stroke, senility and aging, etc., with a possible side effect of increased sexual drive -- to come along since Dr. Carter's Little Liver Pills. The treatment -- which has been in and out of vogue since the '20's -- works very much on the principle of a decompression chamber by drenching the body with massive doses of oxygen. (Mightn't cancer, runaway cell growth, actually thrive on such a procedure?) The tank at Harvard, for example, which was acquired in 1928 and was much publicized when it was used in a last-ditch effort to save Patrick Kennedy's life, has been idle for the past five years. Citing cases of dramatic successes and heartbreaking disappointments, Trimble calls for more research -- and one can only agree, and the sooner the better if we're to head off more faddish hard sells like this. Not likely to win over skeptics or influence the AMA.