Spatiotemporal regulation of the cough motor pattern.

Abstract

The purpose of this study was to identify the spatiotemporal determinants of the cough motor pattern. We speculated that the spatial and temporal characteristics of the cough motor pattern would be regulated separately. Electromyograms (EMG) of abdominal muscles (ABD, rectus abdominis or transversus abdominis), and parasternal muscles (PS) were recorded in anesthetized cats. Repetitive coughing was produced by mechanical stimulation of the lumen of the intrathoracic trachea. Cough inspiratory (CT(I)) and expiratory (CT(E)) durations were obtained from the PS EMG. The ABD EMG burst was confined to the early part of CT(E )and was followed by a quiescent period of varying duration. As such, CT(E )was divided into two segments with CT(E1 )defined as the duration of the ABD EMG burst and CT(E2 )defined as the period of little or no EMG activity in the ABD EMG. Total cough cycle duration (CT(TOT)) was strongly correlated with CT(E2 )(r(2)>0.8), weakly correlated with CT(I )(r(2)<0.3), and not correlated with CT(E1 )(r(2)<0.2). There was no significant relationship between CT(I )and CT(E1 )or CT(E2). The magnitudes of inspiratory and expiratory motor drive during cough were only weakly correlated with each other (r(2)<0.36) and were not correlated with the duration of any phase of cough. The results support: a) separate regulation of CT(I )and CT(E), b) two distinct subphases of CT(E )(CT(E1 )and CT(E2)), c) the duration of CT(E2 )is a primary determinant of CT(TOT), and d) separate regulation of the magnitude and temporal features of the cough motor pattern.