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Filtering facepiece respirators with EV+AVS reduces discomfort, exertion during outdoor duties

Stephen Padilla
01 Aug 2018

Among male military personnel performing prolonged essential outdoor duties, use of filtering facepiece respirators (FFRs) with exhalation valve (EV) and a novel active venting system (AVS) significantly reduces symptoms, discomfort and exertion as compared to FFR with EV and standard N95 FFR, a Singapore study has shown.

Additionally, FFR with EV appears to outclass standard FFR in terms of perceived discomfort, exertion and most symptoms.

Participants accorded significantly better scores to FFR with EV and FFR with EV+AVS than to standard FFR as regards several symptoms. Both FFR with EV+AVS and FFR EV demonstrated significantly less discomfort (FFR with EV+AVS: 91.1 percent; FFR with EV: 57.6 percent) and exertion (FFR with EV+AVS: 83.5 percent; FFR with EV: 34.4 percent) than standard FFR. [Singapore Med J 2018;59:327-334]

In addition, there were significantly better scores for exertion (53.4 percent) and comfort (39.4 percent) with FFR with EV+AVS vs FFR with EV.

“We believe that the improvements noted in the symptoms were likely due to improved ventilation of the dead space within the FFR, which was provided by the AVS,” researchers said. “Apart from ventilating the dead space, as per fluid dynamics modelling, the venting of air through the blower in FFR with EV+AVS resulted in the sucking out of air away from the FFR, thus reducing the likelihood of rebreathing CO2 when compared to the standard FFR.” [PLoS One 2015;10:e0130306]

A study of healthcare workers required to wear FFRs for two 12-hour shifts showed that removals of the respirator were reportedly due to discomfort experienced while wearing them. Another study suggested that workers wanted FFRs that interfered less with breathing and reduced the build-up of heat. [Am J Infect Control 2013;41:1218-1223; Am J Infect Control 2010;38:18-25]

“Our findings that the incorporation of an AVS into the FFR resulted in the reduction of symptoms, exertion and discomfort may prompt improved compliance with [personal protective equipment] among workers who are required to use FFRs for prolonged periods,” researchers said.

However, it is not yet known whether FFR with EV, with or without an AVS, can be used for infection control in the healthcare setting, given that AVS is not meant to be disposable. In addition, disinfection after healthcare procedures would be difficult.

“Further trials are necessary to determine whether these perceived improvements correspond to objectively measurable physiological benefits and improvements in compliance with FFR usage, especially among military personnel and healthcare workers, who may need to use FFRs for prolonged periods of time and for essential duties,” researchers said.

A randomized open-label controlled crossover study was conducted to compare three FFR options (standard FFR, FFR with EV and FFR with EV+AVS). A questionnaire was completed by male military personnel (aged 18–20 years) at the start of outdoor duty (baseline), after 2 hours of standardized nonstrenuous outdoor duty, and after 12 hours of duty divided into 2-hour work-rest cycles.

Using a five-point Likert scale, participants rated the degree of the following: discomfort, exertion and symptoms. A multivariate ordered probit mixed-effects model was used to assess the association between outcomes and types of FFR.

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