Laryngeal paralysis on receptor and reflex responses to negative pressure in the upper airway.

Mechanoreceptors affected by changes in transmural pressure and/or contraction of intrinsic muscles are present in the larynx. This study is designed to test the hypothesis that laryngeal paralysis alters laryngeal mechanoreceptor and reflex responses to collapsing pressure. Experiments were carried out on anesthetized, spontaneously breathing dogs. The activity of 65 mechanoreceptors was recorded from the superior laryngeal nerve during upper airway occlusion before and during laryngeal paralysis induced by cold block of both recurrent laryngeal nerves (RLN). Esophageal and upper airway pressures were also recorded. Thirty-three laryngeal mechanoreceptors stimulated by negative pressure decreased their inspiratory activity during upper airway occlusion from 48.1 to 30.4 imp/sec when the RLNs were blocked. In contrast, 21 inspiratory modulated mechanoreceptors inhibited by negative pressure and 11 responding only to negative pressure did not change their activity during RLN block. The effect of laryngeal paralysis on the cricothyroid muscle response to negative pressure was assessed in 7 dogs and found to be minimal. These results suggest that 'drive' receptors stimulated by negative pressure do not play a significant role in the reflex activation of upper airway dilating muscles.