Correlation of laryngeal chemoreflex severity with laryngeal muscle response.

Abstract

To examine the relationship between the severity of the laryngeal chemoreflex (LCR) and the pattern of laryngeal muscle activity during an LCR-induced apnea. The laryngeal mucosa of 20 piglets aged 17 to 20 days was stimulated under both hypoxic and normoxic conditions. Respiration, blood pressure, and activity of the thyroarytenoid (TA) and posterior cricoarytenoid (PCA) muscles were monitored during the LCR-induced apnea. Hypoxemia resulted in a shorter average apnea duration but a greater degree of hypotension. All piglets recovered spontaneously following normoxic LCR stimulation. Hypoxic stimulation resulted in two divergent apneic responses: transient with a spontaneous recovery (17 piglets) or profound requiring resuscitation (three piglets). An increase in TA muscle activity and a decrease in PCA muscle activity was the most common response to LCR stimulation. The response of the TA and PCA muscles was maintained in piglets destined for spontaneous recovery. Decreasing TA activity and increasing PCA activity correlated with the development of a profound response. The piglet demonstrates two distinct responses to hypoxic laryngeal chemostimulation that correlate with the activity of the intrinsic laryngeal muscles. Failure to maintain the activity of the TA and PCA muscles during a profound response is associated with the development of severe cardiovascular instability. This study suggests that the critical event involving the LCR is the development of complications secondary to hypoxia.