Efficacy of Various Mitigation Devices in Reducing Fugitive Emissions from Nebulizers

Aerosol-Generating Procedures and Virus Transmission

“…Moreover, an adequate interval between tests is required to clean the room air, allowing ambient particle counts to return to baseline. 13,30 An important distinction between the measurements of particle concentrations and exhaled gas dispersion distance is that these measures only reflect the aerosol characteristics; but neither one directly represents the risk of infection via aerosol transmission.…”

“…In the early phases of the pandemic, there were serious concerns that aerosol therapy, especially nebulization, was an AGP and its use could enhance viral transmission and pose a risk to health care workers. 54 Two clinical studies, 47,55 one healthy volunteer study 30 and one in vitro study, 56 reported that aerosol particle concentrations, particularly in small aerosol particles (# 5 mm), in the ambient air increased by $100 times with nebulization (Table 4). Using the smoke light detection technology, Hui et al also reported greater smoke dispersion distances with a small-volume nebulizer (SVN) driven by 6 L/min air than with an oxygen mask at the same gas flow, especially in the simulated scenario of severe lung injury.…”

“…61 Only part of the medical aerosols would be inhaled and deposited in the subject's airway; most of the particles are released or exhaled into the environment, the so-called fugitive aerosol. 30,56 In contrast, bioaerosols are particles that contain microorganisms, such as the aerosol particles exhaled by an infected individual or the aerosols generated by a contaminated nebulizer. Inhaled medical aerosols either deposit in the airways or are exhaled.…”

“…61 Both in vitro and in vivo studies found that the use of SVN with an aerosol mask produced the highest fugitive aerosol concentrations, followed by SVN with mouthpiece, VMN with aerosol mask, and VMN with mouthpiece (Table 4). 30,56 Notably, placing VMN in line with HFNC generates lower fugitive aerosol concentrations than VMN with mouthpiece. 65 Several mitigation strategies are available for different nebulizers with various interfaces (Table 4 and Fig.…”

“…Placing a face tent scavenger with applied negative pressure over a conventional aerosol face mask is equally effective as a filter face mask that incorporates filters at the exhalation ports in reducing fugitive aerosol concentrations for both SVN and VMN. 30 When the filter mask is used, it needs to firmly fit the subject's face to avoid aerosol leakage. Adding an expiratory filter to the mouthpiece during nebulizer use also reduces fugitive aerosol concentrations.…”