Respiratory Drive and Timing during Assisted Ventilation in Dogs

Abstract
In 8 anesthetized dogs, during isocapnic hyperoxia we studied the effect of assisted ventilation (AV) on ventilatory drive, inspiratory off-switch volume (Voff) and duration of inspiratory diaphragmatic activity (Tdi)· Tidal volumes (Vt) during AV were double spontaneous Vt. Two electrodes were inserted in the diaphragm to obtain the electromyogram (EMG). The index of ventilatory drive was the EMG0.3 – i.e., the amplitude of the moving average EMG 300 ms after the onset of inspiratory activity. AV decreased EMG0.3 but had no effect on Voff and Tdi. Vagotomy not only abolished the reduction in drive, but may have increased drive during AV.