Closed–Loop ventilation using sidestream versus mainstream capnography for automated adjustments of minute ventilation—A randomized clinical trial in cardiac surgery patients

Abstract

Background INTELLiVENT–Adaptive Support Ventilation (ASV) is a closed–loop ventilation mode that uses capnography to adjust tidal volume (VT) and respiratory rate according to a user–set end–tidal CO2 (etCO2) target range. We compared sidestream versus mainstream capnography with this ventilation mode with respect to the quality of breathing in patients after cardiac surgery. Methods Single–center, single–blinded, non–inferiority, randomized clinical trial in adult patients scheduled for elective cardiac surgery that were expected to receive at least two hours of postoperative ventilation in the ICU. Patients were randomized 1:1 to closed–loop ventilation with sidestream or mainstream capnography. Each breath was classified into a zone based on the measured VT, maximum airway pressure, etCO2 and pulse oximetry. The primary outcome was the proportion of breaths spent in a predefined ‘optimal’ zone of ventilation during the first three hours of postoperative ventilation, with a non–inferiority margin for the difference in the proportions set at –20%. Secondary endpoints included the proportion of breaths in predefined ‘acceptable’ and ‘critical’ zones of ventilation, and the proportion of breaths with hypoxemia. Results Of 80 randomized subjects, 78 were included in the intention–to–treat analysis. We could not confirm the non–inferiority of closed–loop ventilation using sidestream with respect to the proportion of breaths in the ‘optimal’ zone (mean ratio 0.87 [0.77 to ∞]; P = 0.116 for non–inferiority). The proportion of breaths with hypoxemia was higher in the sidestream capnography group versus the mainstream capnography group. Conclusions We could not confirm that INTELLiVENT–ASV using sidestream capnography is non–inferior to INTELLiVENT–ASV using mainstream capnography with respect to the quality of breathing in subjects receiving postoperative ventilation after cardiac surgery. Trial registration NCT04599491 (clinicaltrials.gov).