Aerosol Delivery to an Adult Model via High-Flow Nasal Cannula with Inspiration-Synchronized Small-Particle Vibrating Mesh Nebulizer

<b><i>Background:</i></b> Aerosol delivery via high-flow nasal cannula (HFNC) with an inspiration-synchronized vibrating mesh nebulizer (VMN) yielded higher inhaled doses than with a continuous VMN. Recently, a prototype VMN generating aerosol particles <3 µm improved aerosol delivery during invasive ventilation in adult and pediatric models, outperforming the conventional VMN. However, the effects of inspiration-synchronized small-particle VMN during HFNC remain unknown. <b><i>Methods:</i></b> An adult manikin was connected to a dual-chamber lung model driven by a ventilator to simulate spontaneous breathing. An HFNC system was utilized with gas flows at 15, 30, and 60 L/min with temperature at 37°C. Both small-particle and conventional VMNs were tested in inspiration-synchronized and continuous modes, with placements at the humidifier inlet and near the nasal cannula. Each experiment involved delivering 1 mL of albuterol (2.5 mg/mL) and was repeated five times. A collecting filter placed at the trachea captured aerosol, which was then eluted and assayed with UV spectrophotometry (276 nm). <b><i>Results:</i></b> When VMN was placed near the nasal cannula, inspiration-synchronized VMN consistently delivered greater inhaled doses compared with continuous VMN, regardless of aerosol particle sizes or HFNC flows (all <i>p</i> < 0.05). When positioned at the humidifier inlet, continuous VMN yielded higher inhaled doses than inspiration-synchronized VMN at 30 and 60 L/min but lower inhaled doses at 15 L/min (all <i>p</i> < 0.05). In the inspiration-synchronized mode, the small-particle VMN delivered greater inhaled doses at HFNC flows of 15 and 30 L/min than the conventional VMN, independent of nebulizer placements (all <i>p</i> < 0.05). The highest inhaled dose was observed with the inspiration-synchronized VMN placed near the nasal cannula and the continuous VMN placed at the humidifier inlet. <b><i>Conclusions:</i></b> In a model of adult transnasal aerosol delivery, the inspiration-synchronized VMN delivered a higher inhaled dose than the continuous VMN when placed near the nasal cannula. The small-particle VMN offers potential for further improvement in aerosol delivery.