Transcutaneous monitoring as a replacement for arterial PCO2 monitoring during nocturnal non-invasive ventilation

SummaryBackgroundContinuous, non-invasive assessment of alveolar ventilation achieved by transcutaneous PCO2 (PtcCO2) monitoring is clearly superior to intermittent, invasive blood gas analyses in patients receiving nocturnal non-invasive positive pressure ventilation (NPPV), but the reliability and accuracy of PtcCO2-monitoring is still disputed. The present study was aimed at investigating the capability of modern PtcCO2-monitoring to reliably assess alveolar ventilation during nocturnal NPPV.MethodsCapillary blood gas measurements (11pm, 2am, 5am and 7am) and 8 h of continuous PtcCO2-monitoring using three of the latest generation devices (SenTec Digital Monitor, Radiometer TCM4-TINA and Radiometer TOSCA500) were performed during polysomnography-proven sleep studies in 24 patients receiving NPPV (15 with COPD, 9 with restrictive disorders).ResultsThe technical calibration drift for SenTec DM, TCM4-TINA and TOSCA500 was 0.1, −0.4 and −0.5 mmHg/h, respectively. Bland-Altman method comparison of PaCO2/drift-uncorrected PtcCO2 revealed a mean bias (limits of agreement) of 1.0 (−4.7 to 6.7), −1.5 (−15.6 to 12.5) and 0.8 (−6.8 to 8.3) mmHg, respectively. Continuous overnight PtcCO2-monitoring detected variations in alveolar ventilation, with median ranges of 12.3 (10.7–14.5) mmHg for SenTec DM, 14.5 (12.5–17.0) mmHg for TCM4-TINA and 11.5 (11.0–13.0) mmHg for TOSCA500 (RM-ANOVA, p < 0.001). The four capillary PaCO2 values ranged by a median of 6.3 (4.7–9.7) mmHg.ConclusionsModern PtcCO2-monitoring is reliable, accurate and robust. Since PtcCO2-monitoring is also non-invasive, does not disrupt sleep quality and provides a more complete picture of alveolar ventilation than intermittent capillary PaCO2, PtcCO2-monitoring should become the preferred technique for assessing alveolar ventilation during nocturnal NPPV.Trial Registration: DRKS00000433 at http://apps.who.int/trialsearch/default.aspx.