Effect of midline laparotomy on the cough reflex in dogs

The present studies were designed to test the hypothesis that midline laparotomy promotes selective inhibition of the transversus abdominis muscle during cough as it does during expiratory threshold loading. Anesthetized dogs were studied in the supine posture, and cough was induced by mechanical stimulation of the airways. Midline laparotomy had virtually no effect on the cough-induced activation of the triangularis sterni or the external oblique. On the other hand, the activation of the transversus abdominis was markedly reduced in all animals. Despite this marked inhibition, however, peak pleural pressure and expiratory flow were preserved. This suggests that this inhibition does not play a significant role in determining the occurrence of bronchopulmonary infection after abdominal surgery.