Computational Fluid Dynamics of Aerosol Deposition during High-Flow Nasal Cannula–Assisted Mask Nebulization: a Case-Based Study
摘要
High-flow nasal cannula (HFNC) therapy, often combined with mask nebulization, enables uninterrupted oxygen delivery in acute respiratory care. However, the effects of the flow rate and the respiratory frequency on aerosol deposition remain elusive. A patient-specific upper-airway model is reconstructed based on high-resolution computed tomography. Computational fluid dynamics (CFD) simulations are conducted for the HFNC flow rates ranging from 0 to 50 L min–1 and respiratory rates of 16, 22, and 28 breaths min–1. The airflow patterns, the pressure distribution, and the regional aerosol deposition are analyzed. The aerosol deposition followed a unimodal distribution, peaking at 20 L min–1. At this flow rate, a coherent inspiratory jet enhance bronchial penetration, whereas the flow rates ≥ 40 L min–1 produce nasal vortices that divert ~12% of particles outward and suppress distal delivery. Aerosol deposition is mainly concentrated in the proximal airways (oropharynx 61%, trachea 18%, and nasal cavity 15%), with bronchial deposition remaining ≤3%. The lower respiratory rates markedly increase distal delivery by prolonging particle residence time; deposition at 16 breaths min–1 more than doubled compared with 28 breaths min–1. Although the airway resistance declines at the higher flow rates, the deposition efficiency remarkably decreases. CFD simulations revealed that aerosol deposition during HFNC-assisted mask nebulization could be influenced by the interaction between external flow and inspiratory dynamics. An HFNC flow rate of ~20 L min–1 maximizes pulmonary deposition at all breathing frequencies, while the lower rates further enhance bronchial delivery. These results challenge the assumption that a higher flow rate universally improves therapeutic outcomes and highlight the need for individualized HFNC flow adjustment to optimize aerosol delivery in clinical practice.