Second place-resident clinical science award 1999: laryngeal chemoreflex severity and end-apnea PaO(2) and PaCO(2)

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. Twenty-five piglets underwent normoxic laryngeal stimulation (Pao(2) > 70 mm Hg); 11 then underwent hypoxic stimulation (Pao(2) 50-65 mm Hg). Cardiovascular and respiratory responses were recorded. Recovery Pao(2) was lower during profound responses (Pao(2) = 45.9 +/- 12.8 mm Hg) than during moderate (Pao(2) = 54.9 +/- 7.5 mm Hg) and mild (Pao(2) = 60.6 +/- 10.3 mm Hg) responses (analysis of variance [ANOVA], P = 0.05). Recovery PaCO(2) did not vary (ANOVA, P > 0.05). Blood pressure and O(2) saturation declined at faster rates with increasing severity of response (ANOVA, P < 0.05 for both). Resumption of respiration after LCR-induced apnea is associated with a consistent level of PaCO(2). The severity of the response is associated with recovery PaO(2) levels.