[External respiration and gas exchange in man exposed to simulated diving at 350 M].

Nine test subjects performed 4 dives in a He-O2 atmosphere at 3.5 MPa for 3-21 days. Their external respiration and gas exchange were measured at rest and maximum physical load. At rest the basic respiratory parameters remained unaltered. However respiratory reserves decreased under the influence of increased gas density. At a maximum workload the power of which proved lowered the ventilation gain was inadequate. This led to CO2 retention in the body and, consequently, to subjects' refusal to continue physical work. Prolonged exposure to 3.5 MPa caused the most significant respiratory changes during the first 3 days and their slight normalization and constancy during subsequent 2.5 weeks. This was, probably, associated with a slight pO2 increase in the breathing gas.