Abstract
The laryngeal protective reflex during deglutition is one of the most important functions of the larynx, in addition to phonation and respiration. Clinicaly, aspiration occurs in the lesion of the neuromuscular system including recurrent laryngeal nerve (RLN) paralysis. In this investigation, particular attention was paid to elucidate the mechanism of aspiration in RLN paralysis. For this purpose, three different experimental procedures were adopted: 1) In the first series of the experiments, electrical activities of the intrinsic and extrinsic laryngeal muscles and subglottal pressure with up and down movements of the larynx were recorded simultaneously during deglutition, using felines with a polygraph unit. 2) In the second series of the experiments, afferent discharge from superior laryngeal nerve (SLN) and RLN were also recorded as same manner as mentioned in the first series. 3) In the third series of the experiments, measurement of subglottal pressure in normal adults and RLN paralysis patients during deglutition was performed. On the basis of the results of the experiments, the following conclusions appear justified; 1) The activities of the intrinsic and extrinsic laryngeal muscles in the feline are highly constant in each deglutition. The result of other investigators have demonstrated that this is also the case for man as well as canine. 2) Subglottal pressure in the feline during deglutition shows the following pattern; the pressure rises with the start of deglutition, temporarily drops during laryngeal elevation and rises again during the downward movement of the larynx, and drops at the end of deglutition. This pattern is not affected by resection of the unilateral RLN. 3) The SLN is involved with the sensory function of the pharynx, larynx and trachea. At least two types of afferent discharge, perhaps from superficial and profound sensory nerves, are suspected. 4) The afferent discharge from the RLN in the larynx and trachea is not as distinct as that from the SLN, and this seems to cor-respond with some various change in thorax. 5) The pattern of subglottal pressure in man during deglutition is the same as that of the patient with RLN paralysis, and also the same as that of the feline.
