Respirator inspiratory and
expiratory breathing resistances impact
ventilation and performance when studied independently. However, it is less clear as to how various combinations of
inhalation and exhalation resistance affect user performance. The present study investigated the performance of 11 individuals during constant
load, demanding work to exhaustion while wearing respirators with eight different combinations of
inhalation and exhalation resistance.
Exercise performance time, performance rating, minute volume, and peak inspiratory and
expiratory airflow were recorded at the end of each test trial, and independent
correlations with
inhalation resistance and exhalation resistance were assessed. The combined impacts of
respirator inhalation and exhalation resistances were quantified as the total external
work of breathing (WOB(tot)) and
correlations between the test variables and WOB(tot) were also examined. Significantly linear decreases in performance were found with increased
inhalation resistances independent of exhalation resistance (R(2) = 0.99;
p < 0.001) and with increased WOB(tot) (R(2) = 0.92;
p < 0.001). Performance also decreased with increased exhalation resistance but
no significant relationships were found. Minute volume decreased linearly with increased
inhalation resistance independent of exhalation resistance (R(2) = 0.99;
p < 0.001), but the linear decrease observed between minute volume and WOB(tot) was weak (R(2) = 0.36;
p < 0.05). These findings suggest that WOB(tot) serves as a reliable estimate of the combined impacts of
respirator inhalation and exhalation resistances on user performance during hard work, but that
inhalation resistance alone serves as a better predictor of
ventilation during
respirator wear.