Persistent small-airways dysfunction after exposure to hyperoxia.

To assess the contribution of hyperoxia to reduced pulmonary function after a deep saturation dive, a shallow saturation dive to a pressure of 0.25 MPa with the same profile of hyperoxic exposure as in a deep saturation dive to 3.7 MPa was conducted. The PO2 was 40 kPa, with periods of 75 kPa for 2 h every 2nd day during the first 14 days, 50 kPa the next 12 days, and a gradual fall to 21 kPa over the last 2 days in decompression. Seven submariners and one professional diver aged 22-27 yr participated. Pulmonary function, including static and dynamic lung volumes and flows and transfer factor for carbon monoxide (TLCO), were measured twice before, immediately after, 1 mo after, and 1 and 3 yr after the dive. As reported previously, there was a significant reduction in TLCO and in maximal expiratory flow rates at low lung volumes immediately after the dive. At the follow-up examinations 1 and 3 yr after, there was no recovery of the maximal expiratory flow rates. Forced midexpiratory flow rate was still reduced by 8.7 +/- 5.6% (P < 0.05) and 9.3 +/- 7.1% (P < 0.01), respectively. Forced expired volume in 1 s and forced vital capacity were not significantly reduced. There was a complete recovery of the TLCO. The findings are consistent with the studies indicating development of airway obstruction in divers, and the findings indicate that exposure to hyperoxia contributes to this effect.