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)