Particulate generation with different oxygen delivery devices

Abstract

Background:The Coronavirus pandemic has a high mortality rate in patients that are mechanically ventilated, which has led to an ever increasing interest in noninvasive forms of oxygenation. The use of these devices has the theoretical risk of increased exposure risk because of possible particulate generation. This study aimed to quantify the particulate generation associated with different oxygen devices. Methods: This was a prospective single center study conducted during September 2020 using ten healthy adult volunteers. Testing was conducted in a negative pressure hospital room using a light scattering particle counter. The oxygen devices used were a nasal cannula, an OxyMask™, a non-rebreathing mask, and a high flow system. Particle measurements were obtained at baseline in the room and then with each oxygen delivery device and prespecified oxygen flow rates. These measurements were obtained different distances from the volunteer with their mouth open. A Wilcoxon/Kruskal-Wallis test was performed on each separate oxygen modality with all flow rates as one model. Results: The particle concentrations were slightly non-significantly increased with the OxyMask™ and nonrebreathing mask at the closest distance measured. As the distance increased, these counts decreased closer to ambient levels. The nasal cannula and high flow nasal cannula particle counts were not significantly different from ambient measurements at either distance. Conclusion: Nasal cannula, OxyMask™, non-rebreathing mask, and high flow oxygen did not generate any additional aerosols or droplets above a baseline room measurement, but further studies are necessary to determine infectious risk.

Aerosol-Generating Procedures and Virus Transmission

“…Seven studies among healthy volunteers and 3 studies among patients with COVID-19 found no significant differences in aerosol particle concentrations between HFNC and conventional oxygen devices or breathing room air (Table 2). 25,[32][33][34][35][36][37][38][39][40][41] More importantly, 6 studies reported higher aerosol particle concentrations with coughing than HFNC at 50-60 L/min. 25,32,33,36,38,40 Jermy et al reported that the quantity of aerosols generated by a minute of coughing would take the subjects 86 h to generate while breathing normally with HFNC.…”

Quantification of aerosol dispersal from suspected aerosol-generating procedures

“…Several recent approaches have investigated aerosol dispersal and spread during oxygen therapies and research is still ongoing to answer these questions [7][8][9][10][11][12][13]. While the present evidence is non-conclusive if HFNC or NIV oxygen treatment has high aerosol dispersal potential, results from recent studies suggests that HFNC and NIV does not lead to significantly increased aerosol dispersal compared to low-flow oxygen modalities [14][15][16][17].…”

“…The airflows used for HFNC and LFNC were similar to what is typically used in the clinic, and to what have been used in recent studies, while our setup with a mesh of sensors in the test chamber was more extensive than other recent studies [11,[14][15][16]18]. Gaeckle et al and Wilson et al used funnels to accurately capture all dispersed aerosols, but this approach does not allow for the ability to measure how aerosols spread spatially from the subject.…”

Generation of Aerosols by Noninvasive Respiratory Support Modalities

“…The database literature search resulted in 1735 potentially relevant studies. After screening, 24 studies remained (eFigure 1 in Supplement 1). Twelve studies investigated both HFNO and NIV, and 3 studies included both patients and healthy volunteers, using different study designs (see eTables 1, 3, and 4 in Supplement 1 for an overview and details of these studies).…”