Discontinuity between inspiratory and postinspiratory diaphragm activity in man and rabbit

Diaphragm activity (Edi, 20 Hz low cutoff) was recorded with great time resolution to ascertain whether there is a discontinuity between its inspiratory and postinspiratory periods in humans. We first determined in anesthetized rabbits that gaps or notches in Edi occurred within 80 msec before and after the end of mechanical inspiration in 70% of the analysable breaths in the esophageal lead and in 77% in direct leads. We then determined from the esophageal lead of 4 conscious subjects that gaps or notches in Edi occurred during the above-defined period in 45% of 682 analysable breaths. In each subject mean of moving average Edi (12 msec averaging interval) was computed out of 14-24 breaths, free of ECG artifacts within 200-250 msec before and after end inspiration. A deep indentation occurred near end-inspiration despite the lack of gaps or notches in 1/2 to 4/5 of these breaths. These results suggest that also in humans postinspiratory diaphragm activity does not represent the decay of inspiratory ramp.