Respiratory responses to exercise in divers at 0.4 MPa ambient air pressure.

OBJECT

This study was carried out to evaluate changes in the breathing pattern of divers during exercise at an elevated ambient air pressure equivalent to a depth of 30 m of seawater.

METHODS

A total of 22 healthy male subjects performed graded bicycle exercise in a dry hyperbaric chamber up to a maximum of 3.5 W kg(-1) body weight at normal (0.1 MPa) and at elevated ambient air pressure (0.4 MPa). The exercise ventilation (VE), tidal volume (VT), breathing frequency (BF), oxygen uptake (VO2), carbon dioxide elimination (VCO2), and heart rate (HR) were measured. Perceived dyspnea was assessed by Borg scale ratings.

RESULTS

Comparison of respiratory indices between conditions (0.1 versus 0.4 MPa) revealed a significant reduction in VE, VT, BF, and HR during exercise at 0.4 MPa. VO2 and VCO2 did not differ significantly between conditions. Likewise, no significant difference between conditions emerged in perceived dyspnea.

CONCLUSION

Ventilation is significantly impaired during heavy bicycle exercise at 0.4 MPa. This is obviously not apparent with regard to subjective perception of dyspnea.