Drug Delivery via Vibrating Mesh Nebulizer With Symmetrical and Asymmetrical High Flow Nasal Cannulas in an Adult Model

Background: Aerosol delivery via high-flow nasal cannula (HFNC) is widely used. Although an asymmetrical cannula may improve clearance of gases within the anatomical dead space, its impact on aerosol delivery compared with the standard symmetrical cannula remains unclear. This study compared drug delivery efficiency between the symmetrical and asymmetrical cannulas under standardized conditions. Methods: An in vitro adult airway model, comprising a manikin and a ventilator-driven dual-chamber lung model, simulated spontaneous breathing to evaluate aerosol delivery. Filter-captured albuterol from a vibrating mesh nebulizer was quantified by spectrophotometry (230 nm) to determine delivery efficiency (the percentage of an inhaled dose of 2.5-mg nominal dose) for the symmetrical and asymmetrical cannulas over HFNC flows of 10–60 L/min with 4 breathing patterns combining quiet (15 breaths/min) or distressed breathing frequency (30 breaths/min) with low (300 mL) or high (600 mL) tidal volume (V T ). Results: During quiet breathing with low V T , the maximum efficiency of albuterol delivery was higher for the asymmetrical versus the symmetrical cannula (mean ± SD, 6.8 ± 1.7% vs 3.3 ± 1.7% at HFNC flow 20 L/min, respectively , P = .002) but not different with high V T (17.4 ± 1.1% vs 17.6 ± 1.1% at HFNC flow 10 L/min , P = .89). Conversely, during distressed breathing, the maximum delivery efficiency was higher for the symmetrical versus the asymmetrical cannula with both low V T (8.1 ± 1% vs 4.8 ± 0.4% at HFNC flow 10 L/min, respectively , P = .008) and high V T (24.2 ± 1.4% vs 16.2 ± 1.4% at HFNC flow 20 L/min , P < .001). Conclusions: The asymmetrical cannula improved aerosol delivery compared with the symmetrical cannula during quiet breathing with low V T . During distressed breathing, however, the symmetrical cannula was more efficient, regardless of V T . Thus, the asymmetrical and symmetrical cannulas may be selected for drug delivery via a vibrating mesh nebulizer with an HFNC in patients with quiet and distressed breathing, respectively.