咳反射における喉頭の役割

Abstract

In this study, we tried to analyze the role of the larynx during coughing. To do this, the activities of the intrinsic laryngeal and major respiratory muscles and the changes in intratracheal pressure were recorded during coughing in both nontracheotomized and tracheotomized conditions.Experiments were carried out using non-anesthetized decerebrate cats. EMGs were recorded by means of bipolar electrodes made from thin (50μm) stainless steel wires implanted into the diaphragm (DIA), the rectus abdominis muscle (RA), the thyroarytenoid muscle (TA) and the posterior cricoarytenoid muscle (PCA). The intratracheal pressure was recorded using a micro-tip catheter pressure transducer. To evoke coughing, a stainless steel wire was inserted through a pin-hole in the trachea, and mechanical stimuli were applied at the tracheobronchial mucosa.The mechanical stimuli consistently evoked a series of coughs. During coughing in both the non-tracheotomized and tracheotomized conditions, the TA, PCA, DIA and RA muscles exhibited burst discharges with a fixed pattern and intratracheal pressure increased up to 80cmH2O. However, the onset of the discharge of the RA muscle during coughing in the tracheotomized condition was significantly earlier than that in the non-tracheotomized condition. These results suggest that the function of the larynx during coughing is not only to ensure the closure of the airway, but also to modulate the phases of the respiratory muscle activity.