Detection of carbon dioxide thresholds using low-flow sidestream capnography in ventilated preterm infants

Abstract

Background: Monitoring CO 2 levels in preterm infants receiving mechanical ventilation is designed to avoid the harmful consequences of hypocapnia or hypercapnia. Capnography is of questionable accuracy for monitoring PCO 2 in preterm infants. Objectives: To determine the accuracy of sidestream capnography in ventilated preterm infants by comparing end-tidal carbon dioxide (EtCO 2) values to mixed venous carbon dioxide pressure (PvCO 2) and to transcuta-neous carbon dioxide pressure (TcPCO 2). Methods: Simultaneous recordings of EtCO 2, TcPCO 2 and PvCO 2 in 37 ventilated preterm infants. The PvCO 2-EtCO 2 gradient was calculated. The Bland-Altman technique and the intra-class correlation coefficient (ICC) were used to assess agreement between methods. The area under the curve (AUC) was calculated. Results: Ninety-nine EtCO 2/PvCO 2 pairs were studied from 37 preterm infants with a mean gestational age of 27.7 ±1.9 weeks and a mean birth weight of 1,003 ± 331 g. The mean PvCO 2-EtCO 2 gradient was 11.2 ± 8.0 mmHg, and the ICC was 0.28. The mean PvCO 2-TcPCO 2 gradient was 0 ± 7.8 mmHg, and the ICC was 0.78. AUCs for EtCO 2 and TcPCO 2 were similar in detecting high or low PvCO 2. Conclusion: Despite an insufficient correlation between EtCO 2 and PvCO 2, capnography was able to detect low and high CO 2 warning levels with a similar efficacy to that of TcPCO 2, and may therefore be of clinical interest. © Springer and ESICM 2009.