Maternal, fetal, and newborn tissue PO2 in sheep measured with galvanic oxygen electrodes

Tissue PO₂ was measured with galvanic oxygen electrodes chronically implanted in maternal and fetal tissues of two pregnant ewes. Labor commenced after 3 days in one ewe and after 11 days in the other. Tissue PO₂ was measured in both newborn lambs. Fetal tissue PO₂ during labor was less than 3 mm Hg but rose to values similar to those found in adult tissues in the newborn period. Function of the electrode and response of the tissue to change in oxygenation was challenged by administration of 100% oxygen to the pregnant ewe or newborn lamb, and by administration of intravenous epinephrine to the ewe. These tests suggested that all electrodes were functioning satisfactorily in vivo and that tissue PO₂ was responding as anticipated. Recalibration of electrodes after removal from the tissues confirmed that their response in vitro was similar to that obtained before implantation.