Respiratory function in the upright, working diver at 6.8 ATA (190 fsw)

The influence of static lung loading on a number of respiratory parameters was investigated in subjects performing graded leg exercise in an upright posture while submerged and breathing air at ambient pressures up to 6.76 ATA. In comparison with a previous investigation of the prone posture, a lesser tendency to dyspnea was observed. Neutral and moderately positive static lung loads were associated with less dyspnea than were negative loads. Several indices of respiratory function remained relatively normal during exercise and exposure to varying static lung loads. However, there was a tendency for hypoventilation and CO2 accumulation during heavy exercise at 190 fsw; this was not strictly correlated with dyspnea or static lung load. We conclude that, if a full face mask is used, breathing gear for divers should provide a static lung load of approximately 0 to +10 cmH2O regardless of the diver's orientation in the water. When possible, divers should assume an upright posture while engaged in strenuous work.