Effects of surgical masks on droplet and aerosol dispersion under various oxygen delivery modalities

Abstract

RationaleAerosol dispersion under various oxygen delivery modalities, including high flow nasal cannula, is a critical concern for healthcare workers who treat acute hypoxemic respiratory failure during the coronavirus disease 2019 pandemic. Effects of surgical masks on droplet and aerosol dispersion under oxygen delivery modalities are not yet clarified.ObjectivesTo visualize and quantify dispersion particles under various oxygen delivery modalities and examine the protective effect of surgical masks on particle dispersion.MethodsThree and five healthy men were enrolled for video recording and quantification of particles, respectively. Various oxygen delivery modalities including high flow nasal cannula were used in this study. Particle dispersions during rest breathing, speaking, and coughing were recorded and automatically counted in each condition and were evaluated with or without surgical masks.Measurements and Main ResultsCoughing led to the maximum amount and distance of particle dispersion, regardless of modalities. Droplet dispersion was not visually increased by oxygen delivery modalities compared to breathing at room air. With surgical masks over the nasal cannula or high-flow nasal cannula, droplet dispersion was barely visible. Oxygen modalities did not increase the particle dispersion counts regardless of breathing pattens. Wearing surgical masks significantly decreased particle dispersion in all modalities while speaking and coughing, regardless of particle sizes, and reduction rates were approximately 95 and 80-90 % for larger (> 5 μm) and smaller (> 0.5 μm) particles, respectively.ConclusionsSurgical mask over high flow nasal canula may be safely used for acute hypoxemic respiratory failure including coronavirus disease 2019 patients.Subject Category List4.13 Ventilation: Non-Invasive/Long-Term/Weaning*This article has an online data supplement, which is accessible from this issue’s table of content online at www.atsjournals.org.

In vitro model for investigating aerosol dispersion in a simulated COVID-19 patient during high-flow nasal cannula treatment

“…Having patients wear surgical masks can reduce the risk of transmission to HCWs ( 13 ). This has been reported in healthy subjects ( 14 ) as well as COVID-19 patients ( 15 ). Reduced dispersion has been confirmed in silica, with computational fluid dynamic simulations reporting that wearing a surgical/procedure mask over HFNC may reduce aerosol droplet dispersion ( 16 ).…”

“…Table 3 outlines the average % reduction in aerosol dispersion using a mitigating measure during HFNC reported in previous in vivo studies ( 14 – 16 , 23 , 24 ) in comparison to this current study using an experimental in vitro model. In contrast to this current study, there were no significant decreases in PNCs with the use of a facemask to mitigate against aerosol dispersion during HFNC at 50 L/min in an in vivo study by Li et al ( 25 ).…”

Safety Assessment of Low-Flow Oxygenation Device: Quasi-Experimental Study

“…Nonetheless, Faraone et al (2021) indicated that the orofacial devices used in non-invasive mechanical ventilation therapies under pressure (CPAP or double pressure levels), or non-mechanical devices such as Boussignac or Pulmodyne CPAP, among others, do not ensure airtightness of the system in any of the cases. These devices were argued against for patients with a high risk of infection, as they represented a risk for the workers’ health (Takazono et al, 2021). Hui et al (2009) measured dispersion of the particles in a piece of equipment that used two different pressure levels with an orofacial mask, finding that it was 0.5 to 0.95 m around the patient through the orifice where the leak took place, and the point where the mask meets the nasal bridge.…”

“…Above the pressure of 3 mmHg, and in shearing conditions, the risk of pressure ulcers multiply (Dobler et al, 2020; Gattinoni et al, 2020; Takazono et al, 2021). In any case, as an added complication, facial interfaces do not have systems in place to measure this pressure; therefore, the masks are fitted intuitively, with excessive pressure observed, increasing discomfort.…”

“…; Bonnesen et al, 2021; Custodero et al, 2021). This discomfort is the reason behind some of the leaks observed in these devices (Gattinoni et al, 2020; Segura Alba et al, 2020; Takazono et al, 2021).…”