Enhanced Aerosol Delivery During High-Flow Nasal Cannula Therapy

BACKGROUND: Aerosolized drug delivery via high-flow nasal cannula (HFNC) decreases as gas flow is increased. To improve aerosol delivery, breath-enhanced jet nebulizer may increase aerosol output. This study tested that hypothesis and compared breath-enhanced jet nebulizer to vibrating mesh nebulizer technology. METHODS: First, in an isolated circuit, breath-enhanced jet nebulizer and vibrating mesh nebulizer aerosol outputs were measured during simulated HFNC by using infused saline solution at rates of 5-60 mL/h. Limits were defined when nebulizer filling was detected. The devices were then tested by using Tc-99m/saline solution to measure maximum rates of aerosol production. After the output experiments, drug delivery was measured in vitro by using a model that consisted of an HFNC circuit interfaced to a realistic 3-dimensional printed head. The Tc-99m/saline solution was infused at rates of 5 to 60 mL/h for the breath -enhanced jet nebulizer and 5 to 20 mL/h for the vibrating mesh nebulizer with HFNC gas flows of 10 to 60 L/min. Aerosol delivery to the trachea was measured by using a shielded ratemeter, which defined the rate of drug delivery (lg NaCl/min). RESULTS: With increasing gas flow, breath-enhanced jet nebulizer output increased to a maximum of 50 mL/h, the vibrating mesh nebulizer maximum was 12 mL/h. At HFNC gas flow of 60 L/min, breath-enhanced jet nebulizer delivered 3.16 to 316.8 lg NaCl/min, the vibrating mesh nebulizer delivered 23.5 to 61.7 lg NaCl/min. For infusion pump flows of 5 to 12 mL/h, the rate of drug delivery was independent of nebulizer type (P 5 .19) and dependent on infusion pump flow (P < .001) and gas flow (P < .001). CONCLUSIONS: Increasing gas flow increased breath-enhanced jet nebulizer output, which demonstrated the effects of breath enhancement. At 60 L/min, breath enhanced jet nebulizer delivered up to 5 times more aerosol compared with conventional vibrating mesh nebulizer technology. Breath-enhanced jet nebulizer delivered a wide range of dose rates at all high flows. In patients who are critically ill, breath -enhanced jet nebulizer technology may allow titration of bedside dosing based on clinical response by simple adjustment of the infusion rate.