Clinical experience on tcPco2during labor

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Abstract
TcPCO2 measurements in the fetus during labor were evaluated by analysing the clinical experience in 224 cases. This additional mode of supervision was performed in combination with continuous cardiotocography (CTG) and intermittend fetal blood sampling (FBA) in cases with suspect, prepathologic or pathologic heart rate patterns. The prechosen meaasuring temperature was 39.degree. C in 105 and 44.degree. C in 119 cases. The normal range of the tcPCO2 was defined by calculating the mean value and two standard deviations in cases without hypoxic complications. The absolute values of the normal range were different according to the measuring temperature, when no correction factor was used. After adjusting the transcutaneous values to the blood gas level by means of the Severinghaus formular no significant differences in the tcPCO2 values were notified for the two applied temperatures (39.degree. C and 44.degree. C). There is an obvious rise of tcPCO2 with the progress of labor. Comparing the tcPCO2 values with the pH values in the fetal blood we found a statistically significant correlation at either temperatures (p < 0.001). Aiming at an early detection of raising acidity in the fetal blood, an action line of 55 mmHg after correction (80 mmHg at 44.degree. C, 63 mmHg at 39.degree. C) is an adequate basis for clinical intervention as all acidotic (pH < 7.20) and the majority of preacidotic value (pH 7.20-7.24) can be excluded. One clinical benefit that can be expected by the additional use of tcPCO2 is the reduction in the necessity of fetal blood sampling in a number of cases with abnormal heart rate patterns. At a measuring temperature of 44.degree. C FBA becomes superfluous in 90%. While operative delivery for fetal distress was performed in only 13% of cases with abnormal CTG, all basies were born in viguorous state (modified Apgar score .gtoreq. 7). The tcPCO2 measurement seems to be a useful additional tool especially in cases with abnormal heart rate patterns and in fetuses with high risk of hypoxia.