Single-probe spectrophotometry in the assessment of fetal oxygenation

Six sheep fetuses were monitored with a single-probe tissue spectrophotometer. This spectrophotometer provides continuous digital output of the index of hemoglobin that is saturated with oxygen. To vary the fetal pO2, each maternal ewe was given room air, 100% oxygen, 12% oxygen, and 100% nitrogen via rebreathing bag. Fetal venous (N = 4) or arterial (N = 2) blood was analyzed for pO2. There was excellent correlation between the index of hemoglobin saturated with oxygen and the fetal pO2. The single-probe spectrophotometer overcomes two of the technical problems encountered when a double-probe spectrophotometer is used.