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. 2020 Jun 10;1(4):521-526.
doi: 10.1002/emp2.12152. eCollection 2020 Aug.

Aerosol risk with noninvasive respiratory support in patients with COVID-19

David C Miller  1 , Paloma Beamer  2   3   4   5 , Dean Billheimer  4   5   6 , Vignesh Subbian  4   7   8 , Armin Sorooshian  3   9 , Beth Salvagio Campbell  10 , Jarrod M Mosier  1   10
Affiliations

Aerosol risk with noninvasive respiratory support in patients with COVID-19

David C Miller et al. J Am Coll Emerg Physicians Open. .

Abstract

Objectives: This study evaluates aerosol production with high-flow nasal cannula (HFNC) and noninvasive positive pressure ventilation (NIPPV) compared to 6 L/min by low-flow nasal cannula.

Methods: Two healthy volunteers were randomized to control (6 L/min by low-flow nasal cannula), NIPPV, or HFNC using block randomization. NIPPV conditions were studied using continuous positive airway pressures of 5, 10, and 15 cm H2O with an FiO2 of 1.0 delivered via full-face mask. HFNC conditions included flow rates of 30 and 40 L/min with an FiO2 of 1.0 with and without coughing. HFNC and low-flow nasal cannula conditions were repeated with and without participants wearing a surgical mask. Six aerosol sizes (0.3, 1.0, 2.5, 5, and 10 µm) and total aerosol mass were measured at 2 and 6 ft from the participant's nasopharynx.

Results: There was no significant difference in aerosol production between either HFNC or NIPPV and control. There was also no significant difference with the use of a procedural mask over the HFNC. There was significant variation between the 2 participants, but in neither case was there a difference compared to control. There was an aerosol-time trend, but there does not appear to be a difference between either flow rate, pressure, or control. Furthermore, there was no accumulation of total aerosol particles over the total duration of the experiment in both HFNC and NIPPV conditions.

Conclusions: HFNC and NIPPV did not increase aerosol production compared to 6 L/min by low-flow nasal cannula in this experiment involving healthy volunteers.

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Conflict of interest statement

The authors report no conflicts of interest.Jarrod M. Mosier and David C. Miller conceived the study idea. Jarrod M. Mosier, David C. Miller, Paloma Beamer, Dean Billheimer, Vignesh Subbian designed the experiment. Jarrod M. Mosier and David C. Miller collected the data. Dean Billheimer performed the statistical analysis. All authors interpreted the results. Jarrod M. Mosier and David C. Miller drafted the initial manuscript and all authors contributed significantly to the revisions. Jarrod M. Mosier takes responsibility for the project as a whole.

Figures

FIGURE 1
FIGURE 1
Main results. Concentration (count/m3) of particles 5–10 µm in diameter under control (low flow nasal cannula at 6 LPM), HFNC (at 30 and 40 LPM with and without a surgical mask), and NIPPV (at 5, 10, and 15 cm H2O) measured at 2 and 6 ft from each participant's nasopharynx. We used particle sizes between 5–10 µm based on recent data from the World Health Organization that SARS‐CoV‐2 is transmitted most commonly by respiratory droplets in that range (WHO reference number: WHO/2019‐nCoV/Sci_Brief/Transmission_modes/2020.2). Values represent means and 95% confidence intervals of 2 participants performing each condition in triplicate
FIGURE 2
FIGURE 2
Aerosol‐time trend. Concentration (count/m3) of particles versus time (indicated by run order) by aerosol size (A‐E). There was an aerosol‐time trend that was most pronounced in the submicrometer aerosol size range (<1.0 µm) in contrast to the supermicrometer size range (panels D and E). Each experimental run has average particle count, and is reflected on the x‐axis in the order they were completed. Runs were randomized by experimental condition. The vertical line represents the transition from HFNC and control conditions to NiPPV and control conditions. For all conditions, there is not a significant temporal trend (f)
See this image and copyright information in PMC

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