THE EFFECTS OF ESOPHAGEAL DISTENSION ON DIAPHRAGM AND LARYNGEAL MUSCLE-ACTIVITY IN THE ANESTHETIZED CAT

The electromyographic (EMG) activities of diaphragm and laryngeal musc les were recorded during oesophageal distension in anaesthetized cats. The responses to distension of the thoracic oesophagus differed from those evoked by distension of the cervical oesophagus. The crural comp onent of the diaphragm (CD) was inhibited by distension of the thoraci c oesophagus; distension of the cervical oesophagus did not affect CD EMG. Thyroarytenoid (TA) muscle EMG increased markedly and consistentl y in response to distension of the cervical oesophagus. Distension of the thoracic oesophagus only produced statistically significant increa ses in TA EMG with high distending volume (10 ml) at the level of the gastro-oesophageal junction. The main abductor of the vocal cords, the posterior cricoarytenoid (PCA) was either unchanged or decreased by o esophageal distension. The electrical activities of left paratendinous diaphragm, left costal diaphragm, internal intercostal and external i ntercostal muscles remained unchanged. The entire pattern would appear to constitute a means to aid passage of a bolus into the stomach, and simultaneously guard the respiratory tract from reflux or aspiration.