Mitigating Fugitive Aerosols during Aerosol Delivery via High-Flow Nasal Cannula Devices

Abstract

Background: Aerosol delivery via high-flow nasal cannula (HFNC) has attracted clinical interests in recent years. However, both HFNC and nebulization are categorized as aerosol generating procedures (AGPs). In-vitro studies raised concerns that AGPs had high transmission risk. Very few in-vivo studies examined fugitive aerosols with HFNC and nebulization via HFNC, and effective methods to mitigate aerosol dispersion are unknown.

Method: Two HFNC devices (Airvo2 and Vapotherm) with or without a vibrating mesh nebulizer (VMN) were compared; HFNC alone, surgical mask over HFNC interface, and HFNC with face tent scavenger were used in a random order for nine healthy volunteers. Fugitive aerosol concentrations at sizes of 0.3-10 µm were continuously measured by particle sizers placed at one and three feet from participants. On a different day, six of the nine participants received six additional nebulizer treatments via VMN or small volume nebulizer (SVN) with mouthpiece with/without an expiratory filter or facemask. In-vitro simulation was employed to quantify inhaled dose with VMN via Airvo2 and Vapotherm.

Results: Compared to baseline, neither HFNC device generated higher aerosol concentrations. Compared to HFNC alone, VMN via Airvo2 generated higher 0.3-1.0 µm particles (all p<.05) but VMN via Vapotherm did not. Concentrations of 1.0-3.0 µm particles with VMN via Airvo2 were similar with VMN and a mouthpiece/facemask but lower than SVN with a mouthpiece/facemask (all p<.05). Placing a surgical mask over HFNC during nebulization reduced 0.5-1.0 µm particles (all p<.05) to levels similar to the use of a nebulizer with mouthpiece and expiratory filter. In-vitro the inhaled dose with VMN via Airvo2 was ≥6 times higher than VMN via Vapotherm.

Conclusion: During aerosol delivery via HFNC, Airvo2 generated higher inhaled dose and consequently higher fugitive aerosols than Vapotherm. Simple measures, such as placing a surgical mask over nasal cannula during nebulization via HFNC, could effectively reduce fugitive aerosol concentrations.