Lung function before and after oxygen diving: a randomized crossover study

Breathing oxygen with a partial pressure of > 50 kPa can cause pulmonary oxygen toxicity (POT). Diffusing capacity for carbon monoxide (DL(CO)) is thought to be a more sensitive indicator of POT than vital capacity (VC). Because diffusing capacity can be measured more specifically using nitric oxide (DL(NO)), we hypothesized that DL(NO) is better able to monitor and exclude POT than DL(CO). To compare changes in lung function after oxygen and air dives which include measurement of DL(NO) and DL(CO). Eleven healthy male divers (mean age 27.5 +/- 3.1 years) made two immersed dives to 150 kPa for three hours on two separate days, during which they randomly breathed 100% oxygen or air. VC, DL(NO) and DL(CO) were measured six times during a 26-hour period on both days and on a third non-diving day. There were no significant changes in DL(CO), DL(NO) or other diffusing capacity or spirometric parameters after either type of dive. Lung function after a single three-hour oxygen dive at a pO2 of approximately 150 kPa is comparable to that after an air dive at the same depth and duration. This suggests that such an oxygen dive does not induce detectable signs of POT. Our hypothesis that DL(NO) is more sensitive than DL(CO) for detection of POT could not be tested because the oxygen exposure did not affect either parameter