Noninvasive monitoring of carbon dioxide in tracheostomized patients during weaning

Abstract

Introduction: Gas exchange monitoring in patients undergoing weaning from mechanical ventilation (MV) is essential and a continuous-noninvasive method is desirable.

Aims and Objectives: Method comparison of PCO₂ between gold standard ABG and noninvasive PCO₂-assessment via end-tidal PCO₂- (PetCO₂) and transcutaneous PCO₂-monitoring (PtcCO₂) in tracheostomized patients during invasive MV.

Methods: PetCO₂ and PtcCO₂ was monitored over a period of 60min during MV. PaCO₂-analysis was performed at beginning, at 30min and 60min. Method comparison by Bland and Altman was performed: PetCO₂ versus PaCO_2, PtcCO₂ versus PaCO₂ and PetCO₂ versus PtcCO_2.

Results: 62 patients were included and 60 completed the study with the following underlying diseases: COPD (n=30), neurological/neuromuscular (n=17), OHS (n=5), congestive heart failure (n=4), pneumonia (n=3) and kyphoskoliosis (n=1). Mean PaCO₂ was 42,4±8,6 mmHg, PetCO₂ 36,5±7,5 mmHg and PtcCO₂ 41,7±8,7 mmHg during 60min of MV. Bland and Altman method comparison is shown in Table.

Conclusions: Both noninvasive methods of PCO₂-measurements can not completely substitute PaCO₂ measurements in patients undergoing weaning from MV. However, PtcCO2 showed more favorable results in method comparison to the gold standard PaCO₂ compared to PetCO₂. Following, transcutaneous but not end-tidal analysis of gas exchange is suggested to be an appropriate surrogate for AGB.