RESPIRATORY RESPONSES TO EXERCISE IN DIVERS AT 0.4 MPA AMBIENT AIR-PRESSURE

Object: This study was carried out to evaluate changes in the breathin g pattern of divers during exercise at an elevated ambient air pressur e equivalent to a depth of 30 m of seawater. Methods: A total of 22 he althy male subjects performed graded bicycle exercise in a dry hyperba ric 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 ven tilation (VE), tidal volume (VT), breathing frequency (BF), oxygen upt ake (VO2), carbon dioxide elimination (VCO2), and heart rate (HR) were measured. Perceived dyspnea was assessed by Borg scale ratings. Resul ts: 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 em erged in perceived dyspnea. Conclusion: Ventilation is significantly i mpaired during heavy bicycle exercise at 0.4 MPa. This is obviously no t apparent with regard to subjective perception of dyspnea.