In Vitro Evaluation of Aerosol Delivery Through a Large-Volume Nebulizer in Healthy and Distressed Breathing Patterns

Abstract

Background: Although the use of a high-flow nasal cannula in oxygen therapy has gained great interest in the last decade, oxygen therapy through a large-volume nebulizer (LVN) is most commonly used. The effect of high flow provided by LVN on nebulized bronchodilator delivery has not been investigated thoroughly. This study aimed to quantify aerosol delivery with a high flow oxygen system through LVN in a simulated, adult, spontaneously breathing lung model.

Methods: An adult intubation mannequin was connected to a dual-chamber test lung to simulate adult healthy (tidal volume [V_T], 500 mL; breathing frequency 15 breaths/min; inspiratory to expiratory ratio [I:E], 1:2) and distressed (V_T, 450 mL; breathing frequency, 30 breaths/min; I:E, 1:2) spontaneous breathing patterns. A small-volume nebulizer (SVN, BesMed Cooperation, Taiwan) was connected to an adult aerosol mask placed on the mannequin. The other end of the T-adaptor for the SVN was connected to an LVN to deliver oxygen at a concentration of 40% generated at oxygen gas flows of 9, 12, and 15 L/min. The total flow was verified using a flow meter (TSI Inc). The SVN was filled with a unit dose of salbutamol (5.0 mg/2.5 mL, GlaxoSmithKline, Australia) and diluted with 0.9% saline to 4 mL. Nebulization was performed until no aerosol was visible, and the process was conducted 10 time. The drug dose delivered distal to the bronchus was collected in a filter, which represented the inhaled drug dose. The drug mass deposited in the filter was determined by UV spectrophotometry at a wavelength of 276 nm.

Results: The mean inhaled drug doses with the nebulizer alone were 7.57 ± 0.52% and 5.99 ± 0.16% (P = 0.006) for the healthy and distressed breathing patterns, respectively. Table 1 compares the inhaled drug doses for the three flows of the LVN and the two breathing patterns. The inhaled dose was significantly low when the gas flow increased from 9 to 12 L/min for the healthy breathing pattern (P < 0.001), but increased at a flow of 12 L/min for the distressed breathing pattern.

Conclusions: The aerosol delivery significantly decreased with an LVN inline. Thus, changes in drug doses depend on the flow and breathing pattern.