High-flow nasal cannula oxygen versus facemask ventilation during anesthesia induction in patients undergoing off-pump coronary artery bypass grafting: an exploratory randomized controlled trial

Patients undergoing off-pump coronary artery bypass grafting (OPCABG) often have limited cardiopulmonary reserve and may be vulnerable to hypoxemia during anesthesia induction and tracheal intubation. High-flow nasal cannula oxygen therapy (HFNC) allows continuous oxygen delivery during laryngoscopy, whereas facemask ventilation (FMV) provides conventional positive-pressure ventilation before intubation but requires mask removal during airway instrumentation. This exploratory randomized controlled trial compared two standardized oxygenation workflows during anesthesia induction in OPCABG patients, focusing on oxygen reserve and short-term peri-intubation physiological and procedure-related outcomes. This single-center, parallel-group, exploratory randomized controlled trial was conducted at a tertiary cardiac center from December 2025 to January 2026. One hundred ASA physical status III–IV adults scheduled for elective OPCABG were randomized 1:1 to the HFNC group or the FMV group. In the HFNC group, 100% oxygen was delivered at 40 L/min for 10 min during preoxygenation and then increased to 60 L/min during apneic oxygenation and laryngoscopy. In the FMV group, patients received 10 min of facemask preoxygenation followed by 3 min of volume-controlled ventilation before intubation; oxygen delivery was interrupted after mask removal. The primary outcome was arterial oxygen partial pressure (PaO 2 ) after 10 min of preoxygenation. Secondary outcomes included arterial blood gas parameters, end-tidal gas concentrations, hemodynamic variables, comfort, and procedure-related safety events. All 100 randomized patients were included in the analysis. PaO 2 after preoxygenation was higher in the HFNC group than in the FMV group [374.0 (64.8) vs. 280.7 (58.1) mmHg; mean difference, 93.3 mmHg; 95% CI, 68.9–117.7; P < 0.001]. The lowest EtO 2 within 2 min after intubation was also higher in the HFNC group [84.4 (3.0)% vs. 77.8 (4.3)%; mean difference, 6.6%; 95% CI, 5.1–8.1; P < 0.001]. At completion of intubation, PaCO 2 was modestly higher and pH was slightly lower in the HFNC group. Peri-intubation hemodynamic variables were broadly similar between groups. Two patients in the HFNC group required rescue facemask ventilation for oxygen desaturation; both recovered promptly and were successfully intubated. No severe hemodynamic instability, refractory new-onset arrhythmia, or failed intubation was observed. During anesthesia induction in high-risk patients undergoing OPCABG, HFNC preoxygenation achieved an oxygen reserve at least comparable to that provided by conventional facemask preoxygenation, with higher PaO 2 after preoxygenation and better preservation of early post-intubation EtO 2 . However, HFNC does not replace effective alveolar ventilation and may be associated with mild CO 2 retention and a decrease in pH; rescue facemask ventilation may still be required in selected patients. HFNC may be considered a feasible adjunctive oxygenation strategy, but its clinical value and safety require further validation in larger multicenter studies. Trial registry This trial was registered at the Chinese Clinical Trial Registry (ChiCTR) on 27 November 2025 with the registration number ChiCTR2500113370. The full trial protocol and statistical analysis plan can be accessed through the Chinese Clinical Trial Registry (ChiCTR) ( https://www.chictr.org.cn/ ).