Responses of the anterolateral abdominal muscles during cough and expiratory threshold loading in the cat

The present study was conducted to determine the pattern of activation of t he anterolateral abdominal muscles during the cough reflex. Electromyograms (EMGs) of the rectus abdominis, external oblique, internal oblique, transv ersus abdominis, and parasternal muscles were recorded along with gastric p ressure in anesthetized cats. Cough was produced by mechanical stimulation of the lumen of the intrathoracic trachea or larynx. The pattern of EMG act ivation of these muscles during cough was compared with that during graded expiratory threshold loading(ETL; 1-30 cmH(2)O). ETL elicited differential recruitment of abdominal muscle EMG activity (transversus abdominis > inter nal oblique > rectus abdominis congruent to external oblique). In contrast, both laryngeal and tracheobronchial cough resulted in simultaneous activat ion of all four anterolateral abdominal muscles with peak EMG amplitudes 3- to 10-fold greater than those observed during the largest ETL. Gastric pre ssures during laryngeal and tracheobronchial cough were at least eightfold greater than those produced by the largest ETL. These results suggest that, unlike their behavior during expiratory loading, the anterolateral abdomin al muscles act as a unit during cough.