Exercise tolerance and pulmonary gas exchange after deep saturation dives

Abstract

Pulmonary function and exercise tolerance were measured before and after three saturation dives to a pressure of 3.7 MPa. The atmospheres were heliox with partial pressures of oxygen of 40 kPa during the bottom phase and 50 kPa during the compression and decompression phase. The bottom times were 3, 10, and 13 days. Decompression time was 13 days. Precordial Doppler monitoring was done daily during the decompression, and an estimate of the total bubble load on the pulmonary circulation was calculated as the accumulated sum of bubble scores recorded for each diver. Nine of the 18 divers had chest symptoms with retrosternal discomfort or nonproductive cough after the dive. There were no changes in dynamic lung volumes. Transfer factor for carbon monoxide was significantly reduced from 12.3 +/- 1.2 to 10.9 +/- 1.3 mmol.kPa-1.min-1 (P less than 0.01), and maximum oxygen uptake was reduced from 3.98 +/- 0.36 to 3.42 +/- 0.37 l/min STPD (P less than 0.01) after the dives. Resting heart rate was increased from 64 +/- 6 to 75 +/- 8 min-1 (P less than 0.01). The ventilatory requirements in relation to oxygen uptake and carbon dioxide elimination were significantly increased (P less than 0.01) after the dives. The physiological dead space fraction of tidal volume was significantly higher and showed an increase with larger tidal volumes (P less than 0.05). Anaerobic threshold estimated from gas exchange data decreased from an oxygen uptake of 2.30 +/- 0.25 to 1.95 +/- 0.28 l/min STPD (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)