Abstract
Background:
Aerosol delivery via high-flow nasal cannula (HFNC) has attracted clinical interest in recent years. Both HFNC and aerosol therapy have been considered as aerosol generating procedure (AGP) during COVID-19 pandemic. However, little is known about the fugitive aerosol concentrations during trans-nasal aerosol delivery and the effective method to reduce the fugitive aerosol concentrations.
Methods:
After approval by the ethic committee in Rush University (20121804-IRB01), 7 healthy volunteers were consented and enrolled in the study. Two HFNC devices (Airvo2 and Vapotherm) were utilized with a vibrating mesh nebulizer (VMN) placed at the inlet of humidifier. Aerosol particle concentrations were compared between the two devices, in a random order of HFNC alone, HFNC with a surgical mask, HFNC with a scavenger face tent, HFNC with VMN, HFNC with VMN and a surgical mask, and HFNC with VMN and a scavenger face tent. HFNC flow was set at the highest level subject could tolerate, and 3mL of saline was placed in VMN for each nebulization. This study was implemented in an ICU room, with 2 aerosol particle sizers placed at 1 and 3 feet away from subjects to measure the fugitive aerosol concentrations at sizes of 0.3 to 10 µm at baseline, before, during and after each experiment. Furthermore, a small in-vitro study was conducted to evaluate inhaled dose with albuterol (2.5mg in 3mL) delivered using VMN via the two HFNC devices, three flow settings (20L, 40L, 60L for Airvo2 and 20L, 30L, 40L for Vapotherm) were used.
Results:
Compared to baseline, both HFNC devices alone did not generate higher aerosol concentrations at all particle sizes. Compared to HFNC alone, nebulization via VMN with Vapotherm device did not generate higher fugitive aerosol concentrations (P > 0.05 for all particle sizes). In contrast, nebulization via VMN with Airvo2 device generated higher fugitive aerosol concentrations at sizes 0.3 to 1.0 µm. Placing a surgical mask or using a scavenger face tent were similar effective in reducing the fugitive aerosol concentrations (Figure 1). In the in-vitro study, the inhaled dose of albuterol was higher with VMN via Airvo2 than Vapotherm with HFNC flow of 20 L ([12.9 ± 0.9]% vs [1.3 ± 0.1]%, P = .05 ) and 40 L ([5.0 ± 0.2]% vs [0.8 ± 0.1]%, P = .05) (Table 1).
Conclusions:
During aerosol delivery via HFNC, Airvo2 generated higher inhaled dose and fugitive aerosol particle concentrations than Vapotherm. Placing a surgical mask or a scavenger face tent could reduce fugitive aerosol concentrations.
Table 1
Flow, L/min
inhaled dose (%)
Inhaled dose%
P
Vapotherm
AIRVO
20
1.3 ± .12
12.9 ± .9
.05
30
.9 ± .1
N/A
N/A
40
.8 ± .1
5.0 ± .2
.05
60
N/A
3.4 ± .1
N/A
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