Laryngeal reflex apnea in the chemodenervated newborn piglet

Abstract

Effects of peripheral arterial chemodenervation on laryngeal reflex apnea were studied in 18 piglets of either sex varying in age from 4-63 days. The distal trachea was cannulated with a cuffed endotracheal tube to secure a free airway and permit ventilatory measurements with a pneumotachograph. The proximal trachea was used to introduce fluids into the larynx. Water elicited apnea, bradycardia and arterial hypertension; saline caused only transient disturbances. Electrical stimulation of the superior laryngeal nerves reproduced, and conduction anesthesia ablated, the effects of water in the larynx. Carotid body contribution to respiratory drive was assessed by the ventilatory responses to increased (100%) and decreased (10%) ambient O2 concentration. These indicated significant peripheral chemoreceptor ventilatory activity from birth with little change in the neonatal period. Ventilatory responses to O2 were ablated by carotid chemodenervation, but there was no change in the duration of laryngeal reflex apnea. Attenuation of laryngeal-induced apnea during postnatal development is independent of peripheral chemoreceptor activity. This may be relevant to the clinical problem of sudden infant death syndrome, in which there are carotid body abnormalities.