Respiratory electromyographic estimates of ventilatory functions in piglets

The best electromyographic (EMG) predictors of respiratory drive (P100), tidal volume (VT) and ventilation (VE) were determined from diaphragmatic (DI) and posterior cricoarytenoid (PCA) EMG measures in 8-48-day-old, anesthetized piglets. Progressive hypercapnia was employed to obtain a wide range of muscle activity. A custom-designed, microcomputer-based system was employed to measure the duration, peak amplitude, rate of rise (initial slope) as well as the summed total and initial (first 100 ms) EMG activity from the DI and the PCA. For each respiratory function, the following combinations of EMG measures were identified as significant predictors using regression analyses: (1) for P100, DI amplitude, PCA initial area and PCA rate of rise; (2) for VT, DI amplitude, PCA duration and DI duration; (3) for VE, DI amplitude, DI initial area, PCA initial area, PCA rate of rise, PCA duration, DI area and DI rate of rise. Thus, whereas the traditionally employed measure of DI amplitude is an important correlate of P100, VT or VE, a complete estimate of these respiratory functions requires the inclusion of initial EMG measures and duration.