Effects of respirator dead space, inspiratory resistance, and expiratory resistance ventilatory loads

The effects of respiratorlike inspiratory resistance (IR), expiratory resistance (ER), and dead space (DS) were assessed in a group of 11 normal volunteers during moderate steady-state (SS) and rapidly incremented (RI) exercise. The physiologic effects of IR were predominant, increasing inspiratory time, duty cycle, and several measures of ventilatory work. Effects of DS appear related to increased minute ventilation and include increasing flow rates and duty cycle and requiring greater ventilatory work; during RI exercise, the DS effect became relatively smaller at higher exercise levels. ER compressed expiratory time. These results characterize the response to IR, ER, and DS loads and suggest that DS may be relatively less physiologically significant than IR.