Transcutaneous carbon dioxide measurements in the fetus during labor

Continuous transcutaneous carbon dioxide partial pressure (tcPco2) was monitored in 40 spontaneous labors. The electrode was attached by glue fixation. An interpretable tracing was obtained in 36 cases. All cases but 2 were normal pregnancies. Thirty-two patients had epidural analgesia while the others had no analgesia. All infants had an Apgar score above 7 at five minutes after delivery and only two had a pH of the umbilical artery of less than 7.16. Mean duration of the recordings was 116 minutes (range: 15-300) and mean time for reaching steady-state was 27 minutes (range: 10-45 minutes). Mean value of tcPco2 was 48 mmHg (SD: 6) before 6 cm of dilatation, 47 mmHg (SD: 8) between 6 and 10 cm, and 47 mmHg (SD: 15) at the second stage of labor. Mean umbilical artery Pco2 was 48 mmHg (SD: 14) and mean umbilical artery pH was 7.25 (SD: 0.06). The range of tcPco2 obtained in these normal cases was 20 to 62 mmHg. Comparison of the results with those of other authors and with previous studies of normal labor and epidural analgesia show a higher tcPco2 compared to scalp Pco2. In contrast to other studies in these series no correlation was found in the series between umbilical artery Pco2 and tcPco2 values. This lack of correlation could be explained either by the small number of cases in which both measurements were available (9 cases) and by the small range of variation or by some inaccuracy in the measurements.(ABSTRACT TRUNCATED AT 250 WORDS)