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.
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