Measurement and processing of fetal transcutaneous Pco2 levels

Because asphyxia is not the only factor influencing fetal heart rhythm, a non-optimal cardiotachogram is not necessarily a sign of fetal distress. It makes further evaluation of the fetal condition advisable, especially determination of the acid-base equilibrium. The method of fetal blood sampling, introduced by Saling, has a number of disadvantages for mother and fetus, because of the invasiveness for both. Further, the measured acid-base equilibrium is only representative for a very short period of time and often repeated micro-blood sampling is necessary. A major problem with regard to determination of the acid-base equilibrium in intermittently obtained fetal blood samples is the inclusion of air bubbles in the sample. When they are introduced into the electrode cuvettes, the measured values cannot be considered reliable. The problem was solved in the Department of Obstetrics and Gynecology of the Vrije Universiteit of Amsterdam with a "pipe" shaped special collecting vessel. Similar measuring results were obtained with the formerly used glass capillary method and the special collecting vessel method. Continuous, non-invasive methods have been pursued to avoid the above mentioned problems. Fetal transcutaneous Po2 measurement has been possible for years, but does not provide adequate information during the important second stage of labor because of methodological problems. Continuous fetal tissue pH surveillance is possible, but it also has an invasive character and is technically difficult to perform, leading to many methodological failures. Recently, continuous transcutaneous Pco2 measurement tcPco2 became available. A good correlation was found with simultaneously measured Pco2 levels in fetal blood samples and with those of umbilical artery blood.(ABSTRACT TRUNCATED AT 250 WORDS)