Fig. (6). Relationship between fetal brachial artery PO₂ and oxyhemoglobin saturation (HbO₂) from fetal sheep.

Blood samples were collected from chronically instrumented fetuses while the ewe was breathing an FiO₂ of 0.12 to 0.21, or within three hours after cesarean section followed by mechanical ventilation with FiO₂ adjusted to achieve PaO₂ ranging between 25 and 50 mmHg. All lambs had PaCO₂ and pH within normal range. Dashed lines denote brachial PaO₂ and HbO₂ levels for fetal lambs near sea level (Loma Linda) or at high altitude (Barcroft facilities at the White Mountain Research Station [WMRS]). Measurements were made in fetal lambs that were 127 to 130 days gestation.