Effect of High-Flow Nasal Cannula Flow on Intrapharyngeal Pressure During Fiberoptic Bronchoscopy Under Deep Sedation

BACKGROUND: The flow reaching the vocal folds may be lower than that at the output of high-flow nasal cannula (HFNC) system. This could be due to upper-respiratory obstruction, oxygen leakage, or other factors. The objective of this study was to observe the effect of flow through a nasopharyngeal airway on intrapharyngeal pressure (IPP) in subjects undergoing fiberoptic bronchoscopy (FOB).

METHODS: Patients scheduled for FOB were invited to participate. Measurements were performed at flows of 0–60 L/min; the subjects wore WN-N95 folding medical protective masks (N95) and either underwent FOB or not. IPP at each flow was recorded following 15 s of ventilation, and the cross-sectional area (CSA) of the gastric sinus was measured before and after FOB. Hypoxemia, reflux aspiration, and other pertinent events were recorded.

RESULTS: Sixty subjects undergoing FOB at the Affiliated Hospital of Jiaxing University participated in this trial from October 2022–September 2023. IPP increased significantly with an increase in flow and also increased after placing the N95 mask with the same flow (P < .001). When results from before to after FOB were compared, the difference in CSA was statistically significant 263.6 (220.7–300.5) mm² vs 305.5 (275.4–329.5) mm², P < .001, but the difference in the risk of reflux aspiration was not statistically significant (0% vs 6.7%, P = .13). Complication rates during treatment were 8.3% for hypoxemia, 0% for reflux aspiration, 1.7% for hypertension, 1.7% for hypotension, 6.7% for tachycardia, 5% for bradycardia, and 10% for postoperative nausea and vomiting.

CONCLUSIONS: HFNC can provide effective oxygen therapy for people undergoing FOB, and increases in IPP with flow in the range of 0–60 L/min may not increase the risk of reflux aspiration.