Mainstream Capnography Correlates Well with Central Venous Carbon Dioxide Levels in Non-intubated Children in PACU

Introduction: Monitoring exhaled Carbon Dioxide (CO2) in non-intubated patients is challenging but has value for detecting hypoventilation, apnoea and hypercarbia. The study investigated a mainstream mask capnography system (cap-ONE (R)) especially designed for children. Aim: To compare the accuracy of peak exhaled CO2 (PexCO(2)) using mainstream mask capnography to partial pressure of central venous CO2 (PcvCO(2)). Materials and Methods: After Institutional Review Board approval, this prospective study was conducted enrolling children (weight range 7-40 kg) undergoing minor procedures who had indwelling central venous access for clinical indications. Infant and paediatric mainstream capnography masks were used according to patient body weight. Central venous blood was collected for analysis of PcvCO(2) during capnography recording. Values for PcvCO(2) and PexCO(2) obtained from mainstream mask capnography monitoring were compared in individual patients. Results: Forty children were enrolled and analysed. All patients had an uneventful anaesthetic course and entered the PACU without respiratory compromise. The average and Standard Deviation (SD) of PcvCO(2) were 47.5 (5.0) mmHg. Measurement error between PexCO(2) at blood sampling was 6.1 (SD; 3.2) mmHg. When PcvCO(2) >50 mmHg and PexCO(2) >45 mmHg from the mask was used as the threshold for hypercapnia the sensitivity was 77%, specificity 96%, and Area Under the Curve (AUC) 0.866 at the time of blood sampling. Conclusion: Measurement error between PexCO(2) and PcvCO(2) was similar to known exhaled- arterial PCO2 difference (4- 6 mmHg). We conclude that a mainstream mask capnography is a reliable method to assess hypoventilation and hypercapnia in non-intubated children.