Spatiotemporal regulation of the cough motor pattern

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 (r²>0.8), weakly correlated with CT_I (r²<0.3), and not correlated with CT_E1 (r²<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 (r²<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.