EFFECTS ON PULMONARY-FUNCTION OF DAILY EXPOSURE TO DRY OR HUMIDIFIED HYPERBARIC-OXYGEN

The purpose of this study was to examine the effects of breathing dry or humidified hyperbaric oxygen on pulmonary function. Pulmonary funct ion tests were performed before and after each of 10 hyperbaric oxygen exposures at 2.5 atmospheres absolute (ATA) for 95 min in a group of 13 patients treated daily by hyperbaric oxygen for problem wounds. Pat ients breathed dry oxygen during five successive sessions and humidifi ed oxygen during the remaining five. No differences were found between forced vital capacities (FVC) and maximal expiratory flows before and after hyperbaric oxygen exposure while breathing dry or humidified ox ygen. Significant differences were found for the changes in the percen tage of FVC expired in 1 s (FEV1%) and mean forced mid-expiratory flow rate during the middle half of the FVC (FEF25-75%) on day 1 alone: de crements of 1.42 and 2.96%, respectively, under dry oxygen, vs. increm ents of 3.93 and 34.4%, respectively, for humidified oxygen. Day-to-da y decrements in the percent changes in FEV1% and FEF25-75% were observ ed while breathing humidified hyperbaric oxygen. These results demonst rate that repeated daily exposure to humidified hyperbaric oxygen abol ishes the initial beneficial effect of humidification on peripheral ai rways flow characteristics. (C) 1997 Elsevier Science B.V.