Air vs. He-O2 recompression treatment of decompression sickness in guinea pigs.

Air vs. He-O2 (20.9% O2) recompression treatment was examined in a model of severe decompression sickness (DCS) using male albino guinea pigs (Cavia porcellus, 500-600 g). Following decompression to the surface from simulated air dives at 200 or 250 fsw, both anesthetized and unanesthetized animals often exhibited responses indicative of a fatal bout of DCS (including hypotension, cardiac arrhythmia, and tachypnea). Upon recompression with air back to depth, good recovery of animals with DCS was observed. Comparison of air vs. He-O2 recompression responses of unanesthetized animals with recompression back to initial depth (200 fsw) revealed a slower recovery from tachypnea with He-O2. Recompression partially back to depth following 200-fsw air dives produced significant differences in the breathing recovery vs. recompression depth relationship between air and He-O2. Treatment effectiveness improved with increasing depth with air, but not with He-O2. These data indicate potential differences in recompression response to air vs. He-O2 when using ventilatory recovery as a measure of effectiveness in treatment of DCS in guinea pigs following air dives.