Effects of industrial respirators on respiratory timing and psychophysiologic load sensitivity.
Loads imposed by industrial respirators include inspiratory flow resistance and dead space. Eleven normal subjects were studied at five levels of treadmill exercise (from resting to peak) with and without a respirator surrogate load (single air-purifying cartridge plus 300 ml dead space). Analysis of variance with linear contrasts was used to separate interpersonal from respirator effects. The respiratory pattern was significantly affected, prolonging inspiration, decreasing peak inspiratory flow rates, and increasing tidal volume. Sensitivity to respiratory loads was measured by the magnitude estimation method; the respirator load, but not exercise, decreased load sensitivity. Interpersonal differences in load sensitivity were relatively large. This study suggests that tolerance to respiratory loads similar to those of respirators may be significantly affected by respiratory timing and load sensitivity adaptation. Poor tolerance by some workers might be related to abnormal psychophysiologic load sensitivity.