A new instrument for the measurement of tissue pO2 of human fetal scalp

Abstract

Measurement of fetal scalp tissue pO2 may be a way of monitoring fetal oxygenation continuously. A membrane-covered flush-type oxygen electrode was developed for this purpose. This electrode measured qualitative changes in tissue pO2. Movement artifacts were reduced by the membrane coating and by the matching of electrode diameter to mean intercapillary distance, the electrode then monitoring mean tissue pO2. Maternal inhalation of 50 per cent oxygen increased scalp tissue pO2. Following normal birth the scalp tissue pO2 increased. Neonatal inspiration of 100 per cent oxygen produced a marked increase in scalp tissue pO2. In one baby born in a poor clinical condition, recovery was mirrored by changes in scalp tissue pO2. In 2 patients with slowing of the fetal heart rate during contractions, scalp tissue pO2 decerased simultaneously. Because the electrode cannot be considered accurately quantitative the information obtained has only been useful in elucidating fetal oxygenation in relation to particular events. At present it has no use in clinical obstetrics.