Effectiveness
Compared to N95 respirator, PAPRs have a higher protection factor with an APF of 25.(67) They filters 99.97% of particles 0.3 µm and are oil proof, is more comfortable for prolonged periods, eliminates the fit problem and can be worn with eyewear and facial hair, and provides full face & head coverage.(1, 23, 100)
While this the recommended respirator for AGPs, it is controversial due to a lack of evidence.(23) Bischoff et al’s influenza exposure model found no detectable level of virus in all (n=29) subjects with PAPR use.(69) Based on HCWs becoming infected during AGPs of patients with SARS despite the use of accepted universal precautions with gowns, caps, gloves, eye protections and N95 masks, PAPR has been recommended for high risk procedures on suspected or confirmed COVID-19 patients.(101, 102) DT Wong reported their institutional use of PAPR resulted in no infection during the SARS outbreak in Toronto.(102) Verbeek JH et al’s 2019 Cochrane review found PAPR better than a PPE without such respirator (RR 0.27, 95% CI 0.17-0.43).(65)
Concurrent use with the N95 respirator to prevent transmission of infection is controversial.(77, 79) N95 in addition to PAPR during AGP has been recommended to supplement the respiratory protection, prevent passage of unfiltered exhalation gases from wearer to the immediate environment, and serve as a backup in the event of a PAPR mechanical failure, or over breathing which may create negative pressure in the PAPR and entrains unfiltered outside air.(103) This was found to multiplicatively increase the mean protection factor of the functioning PAPR, and even in a non-functioning PAPR.(103)