High-flow nasal cannula oxygenation reduces desaturation risk during diagnostic flexible bronchoscopy under deep sedation: a randomized controlled trial

Background: Deep sedation for flexible bronchoscopy (FB) improves procedural conditions but exacerbates desaturation risks. High-flow nasal cannula (HFNC) may mitigate this situation, yet efficacy under deep sedation remains unproven. Methods: In this randomized trial (ChiCTR2400083597), 340 ASA I-II patients undergoing FB under deep sedation (MOAA/S ≤ 1) received conventional nasal cannula (5 L/min; NC) or HFNC (25/45/65 L/min). The primary outcomes were the incidence of intraoperative desaturation (SpO₂ < 90% > 10s) and intraoperative nadir SpO₂ value. The intraoperative VAS scores for cough that reflect the stimulation inhibition as a result of deep sedation were used as secondary outcome. Other evaluated outcomes included the EtCO₂ values before induction and after awakening, incidence of intraoperative hypertension/hypotension, postoperative adverse events, as well as the willingness to undergo re-examination. Results: < 0.05). Cough scores were uniformly low (median VAS:1-1.5), with >97% willingness for repeat FB. Conclusion: The application of HFNC can markedly lower the risks of desaturation during FB under deep sedation in a weak flow-dependent manner, while partially mitigating carbon dioxide accumulation, enabling safer deep sedation without intubation.