Pulmonary gas exchange and urinary electrolyte excretion during saturation-excursion diving to pressure equivalent to 800 and 1000 feet of seawater.

Two subjects carried out a saturation dive to 600 FSW with excursions to 800 feet of seawater (FSW). Two other subjects performed a saturation dive to 800 FSW. Both divers carried out two short excursion dives to 1050 and 1112 FSW followed later by an excursion dive to 1000 FSW lasting for 2-3/4 hours. All four divers noted helium tremors during their first excursion dive at depth exceeding 600 FSW and at very rapid compression rates ranging from 27-40 feet/min. The helium tremors were not observed during the second excursion dive at similar compression rates. In rest and exercise, PA^Q did not change significantly at depth, but showed considerable individual variations. Pulmonary gas exchange at rest remained within normal limits at depths of 800 and 1000 FSW. Exercise performed by two subjects at a moderate work load (100 watts) at 800 and 1000 FSW resulted in an increase of Cv> consumption, whereas CO« excretion tended to decrease. Tidal volume increased and respiratory rate decreased with increasing pressure in rest and exercise. A pronounced reduction in heart rate was observed under both conditions, which was attributed primarily to the effect of inert gas pressure, rather than to the effects of elevated PA . 2 Urinary COg excretion was significantly elevated during the saturation-excursion and decompression periods. The two subjects who complained about muscle pains in the leg, which did not respond immediately to recompression, showed peak urinary C02 excretion at the time the symptoms occurred. Hyperventilation and fluid shifts due to osmotic gradients of dissolved gases have been implicated as the most likely causes of the observed pattern of urinary electrolyte excretion during the saturation-excursion period and the decompression period.