Patient-Centered Ventilator Settings to Reduce Respiratory Acidosis After Cardiac Surgery

BACKGROUND It has been suggested that the implementation of protective mechanical ventilation may increase respiratory acidosis when other ventilator settings, including breathing frequency, are not optimized. After cardiac surgery, this complication may be associated with hemodynamic impact, such as pulmonary hypertension. VentilO is a clinical-decision support system developed to implement protective ventilation. The primary objective of this study was to evaluate the incidence of acid/base disorders after cardiac surgery and to compare the ventilatory parameters set by the clinicians with those proposed by VentilO. This is the first step in validating the VentilO algorithm.

METHODS We conducted a retrospective analysis of the first 100 subjects admitted to the ICU after cardiac surgery in 2023. We recorded demographic and surgical data, the first arterial blood gas at the time of arrival in the ICU, the actual ventilator settings, and the settings recommended by the VentilO algorithm. We compared the minute ventilation and ventilatory parameters set by clinicians with those proposed by VentilO using one-way analysis of variance and Wilcoxon rank-sum test.

RESULTS The prevalence of respiratory acidosis (pH <7.35 and PaCO2 >45 mm Hg) was 38%. Acidosis was associated with the use of lower tidal volumes (56% at 8 mL/kg predicted body weight versus 85% at 6 mL/kg predicted body weight, P = .039). VentilO proposed a higher minute ventilation than what was set by the clinicians for 94/100 subjects (8.4 ± 1.3 vs 6.1 ± 1.2 L/min; P < .001). The mean increase in breathing frequency proposed by VentilO was 5 breaths/min (18 ± 3 vs 13 ± 2 breaths/min, P < .001).

CONCLUSIONS The incidence of respiratory acidosis is high after cardiac surgery and may be lessened using a clinical-decision support system to set postoperative ventilatory parameters.