Correlation of Transcutaneous pCO 2 and Capillary pCO 2 in Newborn Patients Depending on Gestational Age: A Secondary Data Analysis

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Introduction Transcutaneous monitoring of CO 2 partial pressure (tcpCO 2 ) provides continuous information about the CO 2 partial pressure in the blood (pCO 2 ). However, the deviation of tcpCO 2 from pCO 2 is variable. Our aim was to assess whether this deviation depends on gestational age in the first postnatal week. Methods Single‐center secondary data cohort study at a Tertiary Care NICU. 116 neonates undergoing tcpCO 2 monitoring were included. A linear mixed‐effects model was used to analyze the difference between tcpCO 2 and capillary pCO 2 (ΔpCO 2 ) in the first postnatal week. Results 926 simultaneous measurements were included. The evaluation of the linear mixed‐effects model revealed a significant effect of gestational age on ΔpCO 2 . Median [interquartile 1; interquartile 3] ΔpCO 2 was significantly higher for extremely preterm infants (< 28 weeks) with 7.6 [2.4; 13.9] mmHg compared to 3.1 [−1.0; 6.4] mmHg for very preterm (28−31 + 6 weeks), 0.6 [−4.6; 4.7] mmHg for late preterm (32−36 + 6 weeks) and −0.5 [−4.8; 4.7] mmHg for term infants (≥ 37 weeks). There were no significant differences in ΔpCO 2 between patients born at 23 to 25 compared to 26 and 27 completed weeks of gestation. In multivariable analysis, gestational age, early‐onset bacterial infection and capillary pCO 2 were independently associated with ΔpCO 2 , whereas birth weight was not. Conclusions The gestational age has a significant directed effect on the accuracy of transcutaneous CO 2 monitoring in preterm neonates and can—together with other known influence factors—be used to improve the non‐invasive pCO 2 estimation.