Transcutaneous and Arterial Carbon Dioxide Tension during Intermittent Umbilical Cord Occlusion in Fetal Sheep

To study the relationship between arterial PCO2 (PaCO2) and transcutaneous PCO2 (tcPCO2) intermittent 2-min total umbilical cord occlusions were performed with a 3-min interval (n = 12) in 5 fetal sheep, tcPCO2 was measured continuously. Arterial acid-base balance was analyzed at the end of occlusion periods and at the end of occlusion intervals. During each occlusion, PaCO2 increased 1.9 kPa (p0.001) and pH decreased 0.07 units (p0.001). Partial recovery occurred between occlusion intervals resulting in development of mild fetal acidemia. The quick fluctuations in PaCO2 during occlusions were not followed by tcPCO2, but tcPCO2 was capable following the trend in PaCO2. Measurement of tcPCO2 may therefore be an additional tool in the detection of the development of fetal acidemia.