Intraoperative Driving Pressure and Postoperative Pulmonary Complications Following Cardiac Surgery: A Prospective...

Background and Objectives: Postoperative pulmonary complications (PPCs) remain an important cause of morbidity after cardiac surgery. Driving pressure (DP), defined as the difference between plateau pressure and positive end-expiratory pressure, has been proposed as a bedside marker of respiratory system mechanics during lung-protective ventilation. However, its relationship with PPCs in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) remains uncertain. This study aimed to evaluate the association between intraoperative DP and PPCs following CPB-supported cardiac surgery. Materials and Methods: This single-center prospective observational study included 99 adult patients undergoing elective cardiac surgery with CPB. All patients were ventilated using a standardized lung-protective strategy with a tidal volume of 6 mL/kg predicted body weight and a fixed PEEP of 5 cmH₂O. Patients were categorized according to intraoperative DP as Group I (DP < 13 cmH₂O, n = 66) and Group II (DP ≥ 13 cmH₂O, n = 33). The primary outcome was a composite PPC endpoint, defined as the occurrence of at least one EPCO-defined pulmonary complication during the postoperative hospital stay. Multivariable logistic regression was performed to assess whether pre-CPB DP was independently associated with PPCs after adjustment for body mass index, CPB time, and age. Results: Patients with DP ≥13 cmH₂O had higher post-CPB and ICU-admission lactate concentrations. Pneumothorax, pleural effusion, atelectasis, CPAP requirement, and prolonged mechanical ventilation were more frequent in the elevated-DP group. Mechanical ventilation duration, ICU stay, and hospital stay were also longer in this group. Composite PPCs occurred in 41 patients (41.4%). Although higher pre-CPB DP showed a non-significant trend toward increased PPC risk in univariable analysis (OR 1.121, 95% CI 0.988-1.273; p = 0.077), it was not independently associated with the composite PPC endpoint after adjustment (adjusted OR 1.091, 95% CI 0.952-1.251; p = 0.212). In contrast, higher pre-CPB DP was significantly associated with prolonged postoperative ventilation and longer mechanical ventilation, ICU, and hospital stay durations. Conclusions: Elevated intraoperative DP was associated with a higher unadjusted burden of PPCs and delayed postoperative recovery after CPB-supported cardiac surgery. However, pre-CPB DP was not an independent predictor of the composite PPC endpoint after adjustment for relevant confounders. These findings suggest that DP may serve as a clinically useful marker of impaired respiratory mechanics and postoperative vulnerability rather than as an independent causal determinant of PPCs.