Work performance when breathing through different respirator exhalation resistances

This study evaluated performance of individuals exercising at a fixed workl oad and wearing full-facepiece respirators modified to provide expiratory r esistances of 0.27, 0.47, 1.81, 4.43, and 12.27 cmH(2)O . s . L-1. On five separate occasions, 15 volunteers exercised to voluntary endpoint on a trea dmill at fixed speeds and grades chosen to elicit 85% of maximal aerobic ca pacity for an unencumbered condition. Exercise performance time was recorde d at the cessation of each test. Results showed that performance time decre ased linearly (R-2 = 0.79; p <0.001) with increased resistances, and no thr eshold value below which expiratory resistance has no impact on performance was found. Average oxygen consumption rates and minute ventilation also de creased linearly with increased expiratory resistances, indicating that inc reases in expiratory resistance result in a considerable level of hypoventi lation. From the perspective of respirator design, the results of this stud y suggest that the only practical expiratory resistance level limitation is the reduction in performance that will be acceptable to the end users.