Influences of cannula size and flow rate on aerosol drug delivery through the Vapotherm humidified high-flow nasal cannula system.

OBJECTIVE: We investigated the in vitro inspired dose and particle size distribution of albuterol delivered by a vibrating mesh nebulizer through the Vapotherm (Stevensville, MD) humidified high-flow nasal cannula system.

DESIGN: Albuterol (2.5 mg/3 mL) was delivered by an Aeroneb Solo (Aerogen, Galway, Ireland) nebulizer that was connected via adaptor proximal to the nasal cannula and downstream from the Vapotherm 2000i. Albuterol was collected onto an inspiratory filter mounted to a breath simulator programmed with age-appropriate breathing patterns. Particle sizing was completed by cascade impaction. Albuterol was quantified using ultraviolet spectrometry. Measurements were made using varying flow rates through infant, pediatric, and adult nasal cannulae.

SETTING: Aerosol research laboratory.

MEASUREMENTS AND MAIN RESULTS: The inspired dose (percent of nominal dose) for each cannula size and flow rate was 2.5%, 0.8%, 0.4%, and 0.2% for the adult cannula at 5, 10, 20, and 40 L/min, respectively; 1.2%, 0.6%, 0.1%, and 0.0% for the pediatric cannula at 3, 5, 10, and 20 L/min, respectively; and 0.6%, 0.6%, and 0.5% for the infant cannula at 3, 5, and 8 L/min, respectively. Most (62-80%) of the loaded albuterol dose accumulated within the adaptor. For each cannula size, there was a significant decrease in the inspired dose with increasing flow rates, p = 0.026 (infant), p = 0.001 (pediatric), and p < 0.001(adult). The inspired dose increased with increasing cannula size for 5, 10, and 20 L/min (p = 0.007, p < 0.001, and p = 0.005, respectively). The mass median aerodynamic diameter for all trials was less than 5 µm.

CONCLUSION: The amount of albuterol delivered with the Vapotherm system using this model was lower than the amount expected for a clinical response for the majority of flow rates and cannula size combinations. Further studies are needed before routine use of aerosolized albuterol through a Vapotherm high-flow system can be recommended.