Fig. 6.

Incidence of breathing and rapid eye movements in fetal sheep is shown in relation to the calculated mean end-capillary Po₂ of the fetal brain. The incidence of breathing and rapid eye movements declines in dose-dependent manner once the estimated end-capillary Po₂ falls below ∼14 Torr. The incidence of low-voltage electrocortical activity was not significantly reduced over the studied range of fetal Pa_O2. *P < 0.05 compared with normoxia with calculated mean end-capillary Po₂ ∼18 Torr. The corresponding measurements of mean fetal Pa_O2 were ∼25 Torr for normoxia and ∼20, 18, 17 Torr, respectively, for hypoxia. [Modified from Koos et al. (195).]