Abstract
BackgroundCompared to continuous vibrating mesh nebulizer (VMN), inspiration synchronized VMN has shown increased inhaled dose during noninvasive ventilation; however, its use during aerosol delivery via high-flow nasal cannula (HFNC) is still unknown.MethodsAn adult manikin was connected to a dual-chamber model lung, which was driven by a critical care ventilator to simulate spontaneous breathing. A HFNC system was utilized with temperature at 37 ° C while gas flow at 5, 10, 20, 40, and 60 L/min. Inspiration synchronized and continuous aerosol generation were compared at different positions (at the inlet of humidifier vs close to patient). One milliliter of albuterol (2.5 mg/mL) was used in each run (n = 3). Collection filter was placed at the trachea and was removed after each run. Drug was eluted from the filter and assayed with UV spectrophotometry (276 nm).ResultsWhen nebulizer was placed close to patient, inhaled dose was higher with inspiration synchronized than continuous aerosol generation at all gas flows (p = 0.05) except at 5 L/min. When placed at the inlet of humidifier, compared to continuous, inspiration synchronized aerosol generated higher inhaled dose with gas flow set below 50% of patient inspiratory flow [23.9 (20.6, 28.3)% vs 18.1 (16.7, 19.6)%, p < 0.001], but lower inhaled dose with gas flow set above 50% of patient inspiratory flow [3.5 (2.2, 9.3)% vs 9.9 (8.2, 16.4)%, p = 0.001]. Regardless of breathing pattern, continuous aerosol delivered greater inhaled dose with nebulizer placed at humidifier than close to patient at all gas flows except at 5 L/min.ConclusionWhen the HFNC gas flow was set higher than 50% of patient inspiratory flow, no significant advantage was found in inspiration synchronized over continuous aerosol. However, inspiration synchronized aerosol generated 30% more inhaled dose than continuous with gas flow set below 50% of patient inspiratory flow, regardless of nebulizer placement. Continuous nebulizer needs to be placed at the inlet of humidifier.
Highlights
Compared to continuous vibrating mesh nebulizer (VMN), inspiration synchronized VMN has shown increased inhaled dose during noninvasive ventilation; its use during aerosol delivery via high-flow nasal cannula (HFNC) is still unknown
Inhaled dose of inspiration synchronized vs continuous aerosol via VMN For continuous aerosol, when nebulizer was placed close to patient, inhaled dose decreased as gas flow increased, regardless of breathing pattern; when nebulizer was placed at the inlet of humidifier, inhaled dose was similar at 5–20 L/min decreased at 40 and 60 L/min with quiet breathing, while with distressed breathing, inhaled dose increased as gas flow increased from 5 L/min plateaued at 10– 40 L/min
For inspiration synchronized aerosol, inhaled dose peaked at 10 L/min with quiet breathing, regardless of VMN placement; while during distressed breathing, inhaled dose peaked at 20 L/min when nebulizer was placed at the inlet of humidifier, and peak inhaled dose was maintained at 10 and 20 L/min when nebulizer was placed close to the patient (Fig. 2)
Summary
Compared to continuous vibrating mesh nebulizer (VMN), inspiration synchronized VMN has shown increased inhaled dose during noninvasive ventilation; its use during aerosol delivery via high-flow nasal cannula (HFNC) is still unknown. Trans-nasal albuterol delivery for stable patients with chronic obstructive airway diseases has been shown to elicit similar response as conventional nebulization treatment [6,7,8], such as small volume jet nebulizer via mask/mouthpiece or metered dose inhaler with spacer. The currently available commercial product of VMN generates aerosol continuously This continuous production causes the waste of aerosolized medication during patient expiratory phase, which is up to three times longer than the inspiratory phase.
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