Effects of Inspired Oxygen Concentrations During Cardiopulmonary Bypass on the Pulmonary Function of Patients...

Patients with hypertrophic obstructive cardiomyopathy (HOCM) undergoing minimally invasive modified Morrow procedure may be vulnerable to postoperative pulmonary dysfunction. During cardiopulmonary bypass (CPB), lung-protective ventilation has been proposed, but the optimal inspired oxygen concentration under this strategy remains unclear. This study aimed to compare different inspired oxygen concentrations under a fixed lung-protective ventilation strategy during CPB.

This was a prospective clinical observation study involving 97 patients scheduled for modified Morrow procedures via a small right axillary incision between January 2023 and November 2023 at a single center. Patients were randomized to receive CPB ventilation with FiO₂ of 30%, 50%, or 100% under a standardized ultra-low-tidal-volumelung-protective strategy. The primary outcomes included the Horowitz Index (HI = PaO₂/FiO₂), respiratory index (RI = P(A-a)O₂/PaO₂), and alveolar-arterial oxygen pressure difference [P(A-a)O₂] at six different time points within the first 24 h postoperatively, as well as postoperative pulmonary complications. Secondary outcomes included plasma levels of inflammatory cytokines, endothelial glycocalyx (eGC) components, and measures of postoperative rehabilitation and other complications.

There were no significant differences in terms of postoperative complications and rehabilitation among the three groups with different inspired oxygen concentrations under a fixed lung-protective ventilation strategy during CPB. Compared with the 100% FiO₂ group, the 30% FiO₂ group exhibited higher HI at 6 h and 24 h postoperatively with lower P(A-a)O₂ at 18 h and 24 h postoperatively and a lower RI at 24 h postoperatively. In addition, the 30% FiO₂ group showed lower plasma levels of inflammatory cytokines and eGC.

These findings indicate that the use of 30% 100% FiO₂ group with ultra-low tidal volume ventilation during CPB in patients undergoing a modified Morrow procedure via a small right axillary incision was safe and associated with improved early postoperative oxygenation and attenuated inflammatory response. Trial Registration: Chinese Clinical Trial Registry: ChiCTR2400084443.