Fig. 3

Post-inspiratory loading during reverse triggering and premature cycling. A Post-inspiratory loading during reverse triggering. Persistent mechanical effort during the “post-inspiratory” period is evident from the flow tracings, which reveal an attenuated expiratory flow signal indicative of continued diaphragmatic contractile effort. The Pmus waveform is estimated from the Edi waveform and measurement of respiratory neuromuscular coupling (see text for details). The area subtended by the Pmus waveform during the post-inspiratory period (ventilator has cycled off, patient persists with inspiratory effort) is taken as the post-inspiratory effort. In this case, the post-inspiratory loading is attributable to reverse triggering of the patient by the ventilator. B In these tracings, the ventilator cycles off at approximately the peak of diaphragm electrical activity, more than 200 ms prior to the end of neural inspiration in most breaths (red vertical lines). Evidence of persistent mechanical effort during this “post-inspiratory” period is evident from the flow tracings, which reveal an attenuated expiratory flow signal indicative of continued diaphragmatic contractile effort. In this case, the post-inspiratory loading is attributable to premature cycling of the ventilator