Ventilatory interaction between oxygen and carbon dioxide in the preterm primate

Abstract

The steady state ventilatory response to inhaled CO2 was measured in eleven unanesthetized premature Macaca nemestrina during the first 3 wk of life in different steady state background O2 mixtures hypoxia (Fio2 = 0.08 or 0.12), normoxia (Fio2 = 0.21) and hyperoxia (Fio2 = 0.96). Hyperoxic ΔV1/ΔPaco2 and Δ P0.2/ ΔPaco2 were significantly greater than hypoxic ΔV1\ ΔPaco2 and ΔP0.2/ΔPaco2, respectively, at both 2 and 21 days postnatal age by the Mann Whitney test of nonparametric ranking (2 days: 89.6 and 80.2° versus 88.7 and 56.4°, respectively; 21 days: 89.3 and 76.6° versus 50.2 and 57.1°, respectively; p < 0.05). Hypoxic ΔV1/ΔPaco2 was significantly depressed compared to normoxic ΔV1/ΔPaco2 only at 21 days of age (50.2 versus 89.4°, respectively; p < 0.05); hyperoxic CO2 sensitivity and normoxic CO2 sensitivity did not differ at either age. The ventilatory interaction between O2-CO2 in the neonatal primate appears to be the inverse of the typical adult ventilatory interaction. It is hypothesized that differential changes in brain stem blood flow between neonates and adults might explain this difference in O2-CO2 ventilatory interaction. © 1985 International Pediatric Research Foundation, Inc.