Reduced inspiratory drive following laryngeal chemoreflex apnea during hypoxia

Respiratory inhibition following laryngeal water administration was investi gated by breath-by-breath analysis of inspiratory ventilation ((V)over dot I) and central inspiratory drive (P-0.1) in 15 unanesthetized lambs studied in 0.21 FIO2 (Pa-O2: 82-92 torr, Pa-CO2 41-43 torr) and in 0.1 FIO2 (Pa-O2 30-34 torr, Pa-CO2 32-33 torr). During the 30 sec period after stimulation , VI decreased significantly compared to prestimulation levels both in 0.21 FIO2 (- 22, - 21 and - 18%) and in 0.1 FIO2 (- 16, - 23 and - 19%) at 5, 1 6 and 29 days, respectively. In contrast, P-0.1 remained at prestimulation levels during normoxia in all age groups (1, 10 and 9%, NS), but decreased significantly during hypoxia (- 11 and - 13%, P < 0.05) at 16 and 29 days, respectively. Poststimulation apnea duration was significantly related to t he decrease in (V)over dot I (P ( 0.001) but not to the change in P-0.1. La ryngeal stimulation during hypoxemia/ hypocapnia induces a prolonged decrea se of central inspiratory drive in postneonatal lambs, a finding of potenti al significance for the mechanisms of sudden infant death syndrome. (C) 199 9 Elsevier Science B.V. All rights reserved.