EFFECT OF OXYGEN-TENSION AND RATE OF PRESSURE REDUCTION DURING DECOMPRESSION ON CENTRAL GAS-BUBBLES

Reduction in ascent speed and an increase in the O-2 tension in the in spired air have been used to reduce the risk for decompression sicknes s. It has previously been reported that decompression speed and O-2 pa rtial pressure are linearly related for human decompressions from satu ration hyperbaric exposures. The constant of proportionality K (K = ra te/partial pressure of inspired O-2) indicates the incidence of decomp ression sickness. The present study investigated the relationship amon g decompression rate, partial pressure of inspired O-2, and the number of central gas bubbles after a 3-h dive to 500 kPa while breathing ni trox with an O-2 content of 35 kPa. We used transesophageal ultrasonic scanning to determine the number of bubbles in the pulmonary artery o f pigs. The results show that, for a given level of decompression stre ss, decompression rate and O-2 tension in the inspired air can be trad ed off against each other by using pulmonary artery bubbles as an end point. The results also seem to confirm that decompressions that have a high K value are more stressful.