Determinants of Fatal Apnea Responses to Acid Stimulation of the Larynx in Piglets

Abstract

Objectives:

This study explores the physiological determinants of laryngeal chemoreflex (LCR) response severity under hypoxic conditions.

Methods:

Thirty-four piglets underwent hypoxic laryngeal stimulation. Physiologic data were collected, and responses were graded as mild, moderate, or profound.

Results:

Prestimulation hypoxia caused respiratory depression and carbon dioxide retention in profound responders and respiratory stimulation in mild and moderate responders (p < .05). Resumption of respiration occurred in all animals when the Paco2 rose by a mean ± SD of 15.1 ± 6.5 mm Hg (p > .05). There was a significant difference between mild, moderate, and severe responders in change in arterial Pao2 and hydrogenated hemoglobin saturation during the LCR-induced response (p < .001 for both).

Conclusions:

Resumption of respiration is associated with accumulation of arterial Paco2. The respiratory response to hypoxia predicts the severity of the LCR response. The severity of the LCR-induced response is associated with changes in arterial Pao2 and hydrogenated hemoglobin saturation during the LCR-inducedapnea.