Second Place—Resident Clinical Science Award 1999 Laryngeal Chemoreflex Severity and End-Apnea Pao 2 and Paco 2

Abstract

OBJECTIVE: The laryngeal chemoreflex (LCR) is a model for investigating the sudden infant death syndrome. The severity of the LCR-induced response may vary. This study examines the conditions under which recovery from the LCR-induced apnea occurs.

METHODS: Twenty-five piglets underwent normoxic laryngeal stimulation (Pao₂ > 70 mm Hg); 11 then underwent hypoxic stimulation (Pao₂ 50–65 mm Hg). Cardiovascular and respiratory responses were recorded.

RESULTS: Recovery Pao₂ was lower during profound responses (Pao₂ = 45.9 ± 12.8 mm Hg) than during moderate (Pao₂ = 54.9 ± 7.5 mm Hg) and mild (Pao₂ = 60.6 ± 10.3 mm Hg) responses (analysis of variance [ANOVA], P = 0.05). Recovery Paco₂ did not vary (ANOVA, P > 0.05). Blood pressure and O₂ saturation declined at faster rates with increasing severity of response (ANOVA, P < 0.05 for both).

CONCLUSIONS: Resumption of respiration after LCR-induced apnea is associated with a consistent level of Paco₂. The severity of the response is associated with recovery Pao₂ levels.