Effect of a single air dive on pulmonary diffusing capacity in professional divers

Abstract

The aim of this study was to determine whether venous gas embolism after a single air dive, evaluated using precordial Doppler monitoring, was associated with alterations in spirometry, lung volumes, arterial blood gases, or pulmonary diffusing capacity for carbon monoxide (DLCO). Postdive time course monitoring of pulmonary function was undertaken in 10 professional divers exposed to absolute air pressure of 5.5 bar for 25 min in a dry walk-in chamber. The US Navy decompression table was followed. Venous bubbles were detected by precordial Doppler monitoring. Two types of decompression were used: air and 100% O2 applied for 21 min during decompression stops. Spirometry, flow-volume, and body plethysmography parameters were unchanged after the dive with air decompression (AD) as well as with O2 decompression (OD). A significant reduction in arterial PO2, on average 20 Torr, was found after the dive with AD. DLCO was decreased in all divers 20, 40, 60, and 80 min after diving with AD (P < 0.001), whereas it was not significantly decreased after diving with OD. Maximal DLCO decrease of approximately 15% occurred 20 min postdive. In AD diving, maximum bubble grade for each individual vs. maximum DLCO reduction correlated significantly (r = 0.85, P = 0.002), as well as DLCO vs. arterial PO2 (r = 0.64, P = 0.017). In conclusion, a reduction in pulmonary diffusing capacity is observed in parallel with the appearance of venous bubbles detected by precordial Doppler. We suggest that bubbles cause pulmonary microembolization, triggering a complex sequence of events that remains to be resolved. Measuring DLCO complements Doppler bubble detection in postdiving assessment of pulmonary function.