Apnoeic Oxygenation Using High-Flow Oxygen: Effects on Partial Pressure of Carbon Dioxide in Rigid Bronchoscopy

Background/Objectives: Rigid bronchoscopy poses safety challenges due to airway leakage. Although apnoeic oxygenation is a potential strategy, concerns over carbon dioxide (CO₂) retention have limited its adoption. The introduction of high-flow nasal cannula (HFNC) has renewed interest by potentially mitigating CO₂ accumulation during prolonged apnoea. This study investigated changes in the arterial partial pressure of CO₂ (PaCO₂) during apnoeic oxygenation using Optiflow™. Methods: We retrospectively analysed patients undergoing rigid bronchoscopy with HFNC (70 L·min^-1) from 2020 to 2022. The apnoeic period was defined from the onset of apnoeic oxygenation to ventilation resumption. Arterial blood gas levels and complications, including arrhythmia and desaturation, were evaluated. Regression analysis was used to evaluate changes over time. Results: Apnoeic oxygenation was performed in 10 male patients (mean age 65 ± 14 years; body mass index 24.75 ± 4.18 kg·m^-2). The mean duration of apnoea was 33.7 ± 13.7 min, with PaCO₂ rising linearly at 1.50 mmHg/min. No interventions were required to maintain SpO₂ above 91% for all patients. Except for one case of atrial fibrillation that occurred during emergence rather than the apnoeic period, no significant complications were observed. Conclusions: The observed increase in PaCO₂ was lower than in previously reported studies using HFNC via the nares, suggesting that direct delivery of oxygen to the distal airway via bronchoscopy may enhance CO₂ clearance through more effective washout. Apnoeic oxygenation with HFNC could potentially overcome airway leakage for selected patients, but vigilant monitoring remains essential throughout the apnoeic period. Further research is warranted to enhance patient safety.