Background Two non-invasive techniques are available for monitoring carbon dioxide (CO2) in neonatal intensive care unit (NICU) patients. Transcutaneous monitoring (TcCO2) is widely used, whereas the application of end-tidal CO2 (capnography) has been limited in newborn infants, due to accuracy problems.
Objectives To determine in preterm infants the accuracy of end-tidal CO2 (EtCO2) monitoring, and to assess the influence of alveolar plateau duration; to compare EtCO2 and TcCO2 for detecting low and high values of PCO2.
Materials and Methods In 38 preterm infants (birth weight <1500 g) undergoing mechanical ventilation, recordings of EtCO2 (capnography using sidestream device: Capnostream) were performed. Results were compared with those of CO2 venous (umbilical venous catheter) pressure measured from one blood sample (PvCO2), and with simultaneous TcCO2 recordings. In EtCO2/PvCO2 measurement pairs, the bias (EtCO2/PvCO2) and the intraclass correlation coefficient (ICC) were calculated. EtCO2 and TcCO2 techniques were compared for the detection of low (PvCO2 <45 mm Hg) and high PCO2 (PvCO2 >60 mm Hg), using receiver operator characteristic curves (area under the curve, AUC).
Results 104 EtCO2/PvCO2 pairs obtained from 38 patients were analysed. The bias was −1 ± 7.8 mm Hg. It decreased when the alveolar plateau increased. The ICC was 0.28. AUC for EtCO2, compared with TcCO2, were: 0.82 versus 0.89 for high PCO2 (p = 0.18) and 0.89 versus 0.90 for low PCO2 (p = 0.71), respectively.
Conclusion In ventilated preterm infants, the correlation between EtCO2 and PvCO2 was low. Capnography may, however, be useful in the monitoring of CO2 trends.