Peak Acceleration of Respiratory Waveforms at Onset of Inspiration: A New Noninvasive Measure of Respiratory Drive. † 1490

Abstract

Respiratory center drive is most accurately reflected from the steepest rise of the diaphragmatic EMG (Edi) at inspiratory onset. This parameter equates to peak acceleration of diaphragmatic activation (PaEdi) and reflects diaphragmatic recruitment whereas further rise of Edi amplitude (EdiA) signifies continued neuronal discharge. Calibrated respiratory inductive plethysmography (RIP) provides rib cage (RC), abdominal (AB) and their sum(Vt) waveforms noninvasively. We therefore tested the hypothesis that RIP derived acceleration signals (PaRC, PaAB or PaVt) could be used as measures of respiratory drive by validation with PaEdi during unimpeded breathing and obstructed efforts. Five newborn piglets were lightly anesthetized and allowed to breathe spontaneously through cuffed endotracheal tubes. A wire electrode was inserted into the diaphragm using a percutaneous, subcostal approach and RIP transducers applied to the RC and AB compartments. Peak acceleration from RIP waveforms was measured as the highest value in a window range of±300 msec around the mechanical onset of inspiration. The same window was used for PaEdi. Data were displayed and stored on a Respitrace PT16 recorder (Nims, Miami Beach, FL) for subsequent analysis with RespiEvents software. Interventions included 7% CO2 rebreathing and end expiratory obstruction of the endotracheal tube over 2-4 efforts. For CO2 rebreathing, a correlation matrix was calculated for each animal and the means(SD) are listed below; *indicates r with p<.05 in all 5 piglets.Table