Controversies in Respiratory Protective Equipment Selection and Use During COVID-19

One contentious issue during the COVID-19 crisis has been the appropriate selection and use of respiratory protective equipment (RPE) for healthcare workers (HCWs) in hospitals and long-term care settings. As of April 2020, discrepancies exist in the recommendations from health authorities such as the World Health Organization (WHO), Centers for Disease Control and Prevention (CDC), and Canadian Standards Association (CSA). The first of these recommends a surgical mask for routine care and a respirator for high-risk care such as aerosol-generating procedures, while the CDC recommends respirators for all aspects of patient care for these SARS-CoV-2–infected patients, and the CSA risk assessment tool would also result in selection of a respirator.^1-3

Given the contradictory guidance, we will discuss several important considerations for hospital leaders in the implementation of a healthcare respiratory protection program during the current pandemic, including a focused review of the empirical data on surgical mask vs face-fitted respirator (most commonly available in healthcare as N95 in North America), continuous use of the RPE throughout an entire shift vs targeted use when caring for patients, and key areas of uncertainty.

Surgical masks are traditionally used for protection against droplet transmission of respiratory infections, in which large droplets often fall to the ground within short distances; on the other hand, N95 respirators are used for much smaller airborne pathogens, which can remain suspended in the air for long periods of time. Although empiric studies have supported the superiority of respirators over surgical masks in simulated settings (frequently defined as a calculated concentration ratio outside vs inside the RPE), most clinical studies fail to demonstrate a difference in clinical outcomes such as the prevention of respiratory infection. For instance, an exposure study using saline aerosol to simulate viral particles showed that N95 respirators conferred up to 8 to 12 times greater protection against particulate penetration, compared with surgical masks.⁴ However, these advantages of respirators over surgical masks in carefully controlled laboratory studies do not seem to translate to decreased infection risk in real-world settings.

The effectiveness of N95 respirators vs surgical masks in preventing respiratory infections has been evaluated in a small number of clinical randomized, controlled trials (RCTs). We identified five systematic reviews and/or metanalyses published after 2010 and three RCTs published after 1990.^5-12 The RCTs used laboratory-confirmed respiratory virus or clinical infection in HCWs as a clinical outcome, but studies differed in the implementation of RPE use (ie, continuous or targeted use). In a systematic review and metanalysis, Long et al identified six RCTs (9,171 participants) and concluded that, with the exception of laboratory-confirmed bacterial colonization, N95 respirators did not reduce the rate of laboratory-­confirmed influenza, viral respiratory infections, or influenza-like illness among HCWs, compared with surgical masks.⁵ The authors noted risks of bias in these studies owing to the inability to blind and conceal allocation. In addition, the studies focused on infections that are known to transmit via droplet, such as influenza, so the results might not be applicable in the face of a new pandemic in which the important modes of transmission are not yet clear.