Accuracy evaluation of mainstream and sidestream end-tidal carbon dioxide monitoring during noninvasive ventilation: a randomized crossover trial (MASCAT-NIV trial)

Abstract Background The end-tidal partial pressure of carbon dioxide (PETCO2) can be used to estimate the arterial partial pressure of carbon dioxide (PaCO2) in patients who undergo mechanical ventilation via endotracheal intubation. However, no reliable method for measuring PETCO2 during noninvasive ventilation (NIV) has been established. The purpose of this study was to evaluate the correlation and agreement between PaCO2 and PETCO2 measured by these two methods and to compare them in patients who underwent NIV after extubation. Methods This study was a randomized, open-label, crossover trial in a mixed intensive care unit. We included patients who were planned for NIV after extubation and for whom the difference between PETCO2 and PaCO2 was ≤ 5 mmHg. We compared mainstream capnography using an inner cup via face mask (the novel method) with sidestream capnography (the previous method) during NIV. The relationships between PaCO2 and PETCO2 were evaluated by computing the Pearson correlation coefficient, and the agreement between PaCO2 and PETCO2 was estimated using the Bland–Altman method. Results From April 2020 to October 2021, 60 patients were included to the study. PaCO2 and PETCO2 were well correlated in both methods (the novel methods: r = 0.92, P