key: cord-0959282-84z7jgcl authors: Licina, A.; Silvers, A. J.; Stuart, R. title: Use of Powered Air-Purifying Respirator(PAPR) by healthcare workers for preventing highly infectious viral diseases -a systematic review of evidence date: 2020-07-17 journal: nan DOI: 10.1101/2020.07.14.20153288 sha: 5170ff199d61823cb33d6c900bcd29e533863ef8 doc_id: 959282 cord_uid: 84z7jgcl Background Healthcare workers (HCWs) are at particular risk during pandemics and epidemics of highly virulent diseases with significant morbidity and case fatality rate. These diseases include Severe Acute Respiratory Syndrome Coronaviruses, SARS-CoV-1 and SARS-CoV-2, Middle Eastern Respiratory Syndrome (MERS) and Ebola. With the current (SARS-CoV-2) global pandemic, it is critical to delineate appropriate contextual respiratory protection for HCWs. The aim of this systematic review was to evaluate the effect of Powered Air Purifying Respirators (PAPRs) as part of respiratory protection versus another device (egN95/FFP2) on HCW infection rates and contamination. Methods Our primary outcomes included HCW infection rates with SARS-CoV-2, SARS-CoV-1, Ebola or MERS when utilizing PAPR. We included randomized controlled trials, non-randomized controlled trials, and observational studies. We searched the following databases: MEDLINE, EMBASE, and Cochrane Library (Cochrane Database of Systematic Reviews and CENTRAL). Two reviewers independently screened all citations, full-text articles, and abstracted data. Due to clinical and methodological heterogeneity, we did not conduct a meta-analysis. Where applicable, we constructed Evidence Profile (EP) tables for each individual outcome. Confidence in cumulative evidence for each outcome was classified according to the GRADE system. Results We identified 689 studies during literature searches. We included 10 full text studies. A narrative synthesis was provided. Two on-field studies reported no difference in the rates of healthcare workers performing airway procedures during care of critical patients with SARS-CoV-2. A single simulation trial reported a lower level of cross-contamination of participants using PAPR compared to alternative respiratory protection. There is moderate quality evidence that PAPR use is associated with greater heat tolerance but lower scores for mobility and communication ability. We identified a trend toward greater self-reported wearer comfort with PAPR technology in low quality observational simulation studies. Conclusion Field observational studies do not indicate a difference in healthcare worker infection utilizing PAPR devices versus other compliant respiratory equipment. Greater heat tolerance accompanied by lower scores of mobility and audibility in PAPR were identified . Further pragmatic studies are needed in order to delineate actual effectiveness and provider satisfaction with PAPR technology. Please note: Protocol for this review was prospectively registered with the International Register of Systematic Reviews identification number CRD42020184724. . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint B a c k g r o u n d H i g h i n f e c t i v i t y c o m b i n e d w i t h h i g h c a s e f a t a l i t y r a t e d u r i n g t h e C O V I D -1 9 p a n d e m i c h a v e p l a c e d a n e i s s u e d r i l l s a r e u s e d i n t h e a i r w a y ( e g e a r n o s e a n d t h r o a t s u r g e r y , h e a d a n d n e c k s u r g e r y ) S p u t u m i n d u c t i o n E x t e n s i v e d e n t a l p r o c e d u r e s B r o n c h s o c o p y a n d b r o n c h o a l v e o l a r l a v a g e . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint 4 E n d o t r a c h e a l i n t u b a t i o n a n d e x t u b a t i o n F a c e -m a s k v e n t i l a t i o n N o n -i n v a s i v e v e n t i l a t i o n ( e . g . , B i P A P , C P A P ) V e n t i l a t i o n w h e n t h e a i r w a y i s n o t s e a l e d T r a c h e o s t o m y C a r d i o p u l m o n a r y r e s u s c i t a t i o n N a s o g a s t r i c t u b e i n s e r t i o n D e n t a l d r i l l i n g p r o c e d u r e . r e s p i r a t o r y f i l t r a t i o n l e v e l s a r e d e t e r m i n e d a c c o r d i n g t o O c c u p a t i o n a l H e a l t h a n d S a f e t y A d m i n i s t r a t i o n ( O S H A ) s t a n d a r d 2 9 C F R 1 9 1 0 . 1 3 4 " R e s p i r a t o r y P r o t e c t i o n " ( 1 3 ) . M e a n w h i l e , t h e E N r e q u i r e s 9 4 a n d 9 9 % e f f i c i e n c i e s f o r F F R s , c l a s s P 2 ( F F P 2 ) a n d c l a s s P 3 ( F F P 3 ) , r e s p e c t i v e l y ( 1 4 ) . I n E u r o p e r e s p i r a t o r s a r e t e s t e d a g a i n s t t h e r e l e v a n t E u r o p e a n S t a n d a r d a n d a r e a p p r o v e d t o t h e P P E D i r e c t i v e 8 9 / 6 8 6 / E E C o r t h e r e p l a c e m e n t P P E R e g u l a t i o n ( E U ) 2 0 1 6 / 4 2 5 ( 1 5 ) . T h e a s s i g n e d p r o t e c t i o n f a c t o r ( A P F ) o f a r e s p i r a t o r d e n o t e s t h e l e v e l o f p r o t e c t i o n t h a t t h e r e s p i r a t o r i s e x p e c t e d t o p r o v i d e t o u s e r s w h o a r e p r o p e r l y f i t t e d a n d t r a i n e d . T h e A P F i s t h e r a t i o o f p o l l u t a n t o u t s i d e t h e d e v i c e ( e n v i r o n m e n t ) t o t h a t i n s i d e t h e d e v i c e ( i n h a l e d c o m p o n e n t ) . F o r e x a m p l e , a n A P F o f 1 0 " m e a n s t h a t a u s e r c o u l d e x p e c t t o i n h a l e n o m o r e t h a n o n e t e n t h o f t h e a i r b o r n e c o n t a m i n a n t p r e s e n t " . A i r b o r n e l e v e l p r o t e c t i o n i n c l u d e s : h e l m e t s , c o v e r s , h o o d s ; F F P 3 o r F F P 2 / N 9 5 m a s k s , g o o g l e s o r f a c e s h i e l d s ( i f n o h e l m e t s ) . is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint R e s p i r a t o r N 9 5 9 5 % 1 0 f o l d N 9 9 F F P 3 9 9 % 1 0 f o l d 2 0 f o l d P 1 0 0 9 9 . 9 7 % 1 0 f o l d 2 0 f o l d A i r p u r i f y i n g R e s p i r a t o r ( A P R ) A P R h a l f f a c e p i e c e A P R h a l f f a c e p i e c e A s p e r s e l e c t e d f i l t e r ; 1 E x p l a n a t i o n : P l e a s e n o t e : " M i n i m u m f i l t r a t i o n c a p a c i t y t e n d s t o b e a u n i f i e d m e a s u r e f o r a n y a n d a l l p a r t i c l e s w h e t h e r b i o l o g i c a l o r p a r t i c u l a t e . " P A P R s c a n b e d e s c r i b e d a s r e s p i r a t o r s t h a t p r o t e c t t h e u s e r b y f i l t e r i n g o u t c o n t a m i n a n t s i n t h e a i r a n d u s e a b a t t e r y -o p e r a t e d b l o w e r t o p r o v i d e t h e u s e r w i t h c l e a n a i r t h r o u g h a t i g h t -f i t t i n g r e s p i r a t o r , a l o o s e -f i t t i n g h o o d , o r a h e l m e t . T h e r e i s a w i d e h e t e r o g e n e i t y o f t h e a v a i l a b l e P A P R d e v i c e s . T r a d i t i o n a l P A P R s u s e d i n h e a l t h c a r e s e t t i n g s h a v e a f u l l -f a c e p i e c e a n d l o o s e -f i t t i n g h o o d s , a t t a c h e d t o w a i s t m o u n t e d b e l t b a t t e r i e s . P A P R s u s e h i g h -e f f i c i e n c y p a r t i c u l a t e a i r ( H E P A ) f i l t e r s a n d p r o v i d e a h i g h e r l e v e l o f p r o t e c t i o n t h a n d i s p o s a b l e r e s p i r a t o r s . H i g h -e f f i c i e n c y p a r t i c u l a t e a i r ( H E P A ) f i l t e r s h a v e a s i m i l a r f i l t r a t i o n a s P 1 0 0 ( i . e . , t h e y f i l t e r a t l e a s t 9 9 . 9 7 % o f p a r t i c l e s 0 . 3 μ m i n d i a m e t e r a n d a r e o i l p r o o f ( 9 ) . P A P R ' s a r e c o n s i d e r e d m o r e p r o t e c t i v e i n t e r m s o f t h e l e v e l o f r e s p i r a t o r y p r o t e c t i o n d u e t o t h e h i g h e r e f f i c i e n c y o f t h e i r f i l t r a t i o n p i e c e s a s w e l l a s t h e m a i n t e n a n c e o f o u t w a r d p o s i t i v e p r e s s u r e . P A P R s a r e s p e c i f i e d f o r h i g h -h a z a r d p r o c e d u r e s b e c a u s e t h e y c a n o f f e r a s s i g n e d A P F s r a n g i n g f r o m 2 5 t o 1 , 0 0 0 , w h i c h r e d u c e t h e r i s k m o r e t h a n t h e p r o t e c t i o n f a c t o r s p r o v i d e d b y N 9 5 r e s p i r a t o r s . T h e i m p r o v e d p r o t e c t i o n i s l a r g e l y p r o v i d e d b y t h e p o s i t i v e p r e s s u r e i n t h e h e a d c o v e r i n g o r f a c e p i e c e ( T a b l e 2 ) . T h e h o o d s o f P A P R s c a n p r o v i d e s p l a s h p r o t e c t i o n a n d s o m e d e g r e e o f e y e p r o t e c t i o n ( 1 4 , 1 6 ) . I f H C W s a r e p r o v i d e d w i t h s u f f i c i e n t c o m f o r t a b l e a n d w e l l -f i t t i n g r e s p i r a t o r y p r o t e c t i o n , i t i s l i k e l y t h a t c o m p l i a n c e w i t h p r e v e n t i v e p r o g r a m s w i l l b e i n c r e a s e d ( 1 7 ) . . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint H o w t h e i n t e r v e n t i o n m i g h t w o r k I n t h e f i r s t i n s t a n c e , r e l e v a n t i n d i v i d u a l i n s t i t u t i o n s n e e d t o s a f e g u a r d a n H C W r e s p i r a t o r y c o m p l i a n c e p r o g r a m . A p p r o p r i a t e c h o i c e o f t h e l e v e l o f r e s p i r a t o r y p r o t e c t i o n n e e d s t o b e m a d e w i t h i n t h i s p r o g r a m . T h e r e i s s i g n i f i c a n t h e t e r o g e n e i t y o f i n t e r n a t i o n a l r e c o m m e n d a t i o n s w i t h r e g a r d s t o a p p r o p r i a t e r e s p i r a t o r y p r o t e c t i o n f o r H C W s w h e n p e r f o r m i n g A G P s i n s u s p e c t e d o r c o n f i r m e d C O V I D -1 9 p a t i e n t s i s n o t a b l e . E u r o p e a n C e n t r e f o r D i s e a s e P r e v e n t i o n a n d C o n t r o l ( E C D C ) p r e v e n t i o n a n d C e n t r e f o r D i s e a s e C o n t r o l ( C D C ) U S A r e c o m m e n d u s e o f a n l e a s t N 9 5 / F F P 2 a n d h i g h e r l e v e l o f p r o t e c t i o n ( 1 8 ) ( 7 ) ; P u b l i c H e a l t h E n g l a n d r e c o m m e n d s F F P 3 l e v e l r e s p i r a t o r y p r o t e c t i o n i n a d d i t i o n t o s t a n d a r d P P E ( 1 9 ) ; T h e C o m m u n i c a b l e D i s e a s e N e t w o r k A u s t r a l i a ( C D N A ) r e c o m m e n d s F F P 2 / N 9 5 m a s k ; W i t h r e g a r d s t o t h e u s e o f P A P R C D N A r e c o m m e n d s t h a t i f a h e a l t h c a r e w o r k e r i s r e q u i r e d t o r e m a i n i n t is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint . n t e n a n c e a n d c l e a n i . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . n s i d e r e d b l i n d i n g s e p a r a t e l y f o r d i f f e r e n t k e y o u t c o m e s w h e r e n e c e s s a r y . W e u s e d t h e r i s k o f b i a s a s s e s s m e n t i n i n d i v i d u a l s t u d i e s t o i n f o r m o u r a s s e s s m e n t o f s t u d y l i m i t a t i o n s a c r o s s t h e b o d y o f e v i d e n c is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. p r e c a u t i o n s w i t h e i t h e r P A P R ( n = 5 0 ) ; g o g g l e s , F F P 2 / N 9 5 m a s k w i t h a f a c e s h i e l d ( n = 2 2 ) o r g o g g l e s , F F P / N 9 5 w i t h a f u l l h o o d w i t h o u t p o s i t i v e p r e s s u r e ( n = 1 3 0 ) ( 4 1 ) . A s i n g l e r a n d o m i z e d c o n t r o l l e d t r i a l e v a l u a t e d t h e e f f e c t i v e n e s s o f t r a i n i n g p r o g r a m s o n c o n t a m i n a t i o n o f p e r s o n a l p r o t e c t i v e e q u i p m e n t i n c o r p o r a t i n g P A P R ( 4 9 ) . . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint . F o r n o n -r a n d o m i z e d s t u d i e s ( N R S ) , w e i d e n t i f i e d a h i g h r i s k o f b i a s a c r o s s t h e c o n f o u n d i n g , s e l e c t i o n b i a s a n d b l i n d i n g o f o u t c o m e a s s e s s m e n t a c r o s s o b j e c t i v e a n d s u b j e c t i v e d o m a i n s . F o r N R S s t u d i e s , w e i d e n t i f i e d u n c l e a r r i s k o f b i a s a c r o s s t h e b l i n d i n g p e r f o r m a n c e b i a s a n d d e t e c t i o n b i a s , o b j e c t i v e o u t c o m e s . W e u s e d t h e r i s k o . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. I n l i n e w i t h s u b j e c t i v e r e p o r t s t h a t P A P R m a y b e m o r e e f f e c t i v e i n d e c r e a s i n g t h e e f f o r t n e e d e d t o m a i n t a i n t h e w o r k o f b r e a t h i n g c o m p a r e d t o a m o r e c o n v e n t i o n a l f i l t e r i n g f a c e p i e c e , w e i d e n t i f i e is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . A l t h o u g h s o m e a u t h o r s m a k e r e c o m m e n d a t i o n s f o r t h e u s e o f P A P R f o r c r i t i c a l c a r e o f C o v i d -1 9 p a t i e n t s , t h e y a c k n o w l e d g e t h a t t h e r e i s n o c o n c l u s i v e e v i d e n c e t o s h o w t h a t t h i s a d v a n c e d r e s p i r a t o r y t e c h n o l o g y d e c r e a s e s t h e l i k e l i h o o d o f v i r a l a i r b o r n e t r a n s m i s s i o n ( 6 1 ) . . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. e e f f e c t i v e n e s s a n d u t i l i t y o f P A P R i n p r o t e c t i n g t h e h e a l t h c a r e w o r k e r s f r o m c r o s s -i n f e c t i o n d u e t o o t h e r h i g h l y v i r u l e n t v i r a l d i s e a s e s i n c l u d i n g S A R S -C o V -1 , E b o l a o r M E R S . E v i d e n c e b a s e o f l o w q u a l i t y i n d i c a t e s g r e a t e r w e a r e r p r o t e c t i o n i n H C W s u s i n g P A P R c o m p a r e d t o a l t e r n a t i v e r e s p i r a t o r y d e v i c e s , f r o m c r o s s -c o n t a m i n a t i o n a n d d u r i n g d o f f i n g i n s i m u l a t i o n s t u d i e s . P r o v i d e r s a t i s f a c t i o n a p p e a r . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. o u t b r e a k r e s p o n s e m e a s u r e s i n a l a r g e t e r t i a r y h o s p i t a l i n S i n g a p o r e . C a n a d i a n j o u r n a l o f a n a e s t h e s i a = J o u r n a l c a n a d i e n d ' a n e s t h e s i e . 2 0 2 0 : 1 -1 4 . 2 8 . S w a r t z M K . T h e P R I S M A s t a t e m e n t : a g u i d e l i n e f o r s y s t e m a t i c r e v i e w s a n d m e t a -a n a l y s e . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint , I b r a h i m I B , L i m T K . T h e c h a n g i n g f a c e o f h e a l t h c a r e w o r k e r p e r c e p t i o n s o n p o w e r e d a i r -p u r i f y i n g r e s p i r a t o r s d u r i n g t h e S A R S o u t b r e a k . R e s p i r o l o g y . 2 0 0 5 ; 1 0 ( 1 ) : 1 0 7 -1 0 . 5 6 . B o a r d o n H e a l t h S c i e n c e s P , I n s t i t u t e o f M . T h e N a t i o n a l A c a d e m i e s C o l l e c t i o n : R e p o r t s f u n d e d b y N a t i o n a l I n s t i t u t e s o f H e a l t h . T h e U s e a n d E f f e c t i v e n e s s o f P o w e r e d A i r P u r i f y i n g R e s p i r a t o r s i n H e a l t h C a r e : W o r k s h o p S u m m a r y . W a s h i n g t o n ( D C ) : N a t i o n a l A c a d e m i e s P r e s s ( U S ) C o p y r i g h t 2 0 1 5 b y t h e N a t i o n a l A c a d e m y o f S c i e n c e s . A l l r i g h t s r e s e r v e d . ; 2 0 1 . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. A n a l y s i s o f t w o c e n t r e d a t a b y a p a n e l o f i n t e r n a t i o n a l e x p e r t s w h e r is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . . C h u g h t a i A A , C h e n X , M a c i n t y r e C R . R i s k o f s e l f -c o n t a m i n a t i o n d u r i n g d o f f i n g o f p e r s o n a l p r o t e c t i v e e q u i p m e n t . A m e r i c a n j o u r n a l o f i n f e c t i o n c o n t r o l . 2 0 1 8 ; ( n o p a g i n a t i o n ) . 4 . E l -B o g h d a d l y K , W o n g D J N , O w e n R , N e u m a n M D , P o c o c k S , C a r l i s l e J B , e t a l . R i s k s t o h e a l t h c a r e w o r k e r s f o l l o w i n g t r a c h e a l i n t u b a t i o n o f p a t i e n t s w i t h C O V I D -1 is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. Q u e s t i o n : P A P R c o m p a r e d t o E -R C P f o r r e s p i r a t o r y p r o t e c t i o n i n h e a l t h c a r e w o r k e r s d e a l i n g w i t h p a t i e n t s i n f e c t e d w i t h h i g h l y v i r u l e n t v i r a l d i s e a s e s ? S e t t i n g : A e r o s o l G e n e r a t i n g P r o c e d u r e s o r P r o l o n g e d C o n t a c t w i t h I n f e c t e d P a t i e n t s B i b l i o g r a p h y : Z a m o r a 2 0 0 6 ( 1 ) C h u g h t a i 2 0 1 8 ( 2 ) ; C e r t a i n t y a s s e s s m e n t № o f p a t i e n t s E f f e c t C e r t a i n t y I m p o r t a n c is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 17, 2020. . e c o n d a r y O u t c o m e s : 1 . l e v e l o f w e a r e r c o m f o r t , v i s i b i l i t y a n d a u d i b i l i t y w h i l s t u s i n g t h e P A P R o v e r a l t e r n a t i v e r e s p i r a t o r y p r o t e c t i o n ; 2 . o b j e c t i v e a n d / o r s u b j e c t i v e m e a s u r e s o f w o r k o f b r e a t h i n g d u r i n g t h e u s e . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . https://doi.org/10.1101/2020.07.14.20153288 doi: medRxiv preprint o f s t u d i e s S t u d y d e s i g n R i s k o f b i a s I n c o n s i s t e n c y I n d i r e c t n e s s I m p r e c i s i o n O t h e r c o n s i d e r a t i o n s P A P R o t h e r r e s p i r a t o r y p r o t e c t i o n R e l a t i v e ( 9 5 % C I ) A b s o l u t e ( 9 5 % C I ) S e l f -r e p o r t e d p e r c e p t i o n o f h e a t b u i l d u p a s a m e a s u r e o f w e a r e r c o m f o r t 2 S c h u m a c h e r e t a l 2 0 1 3 A n d S c h u m a c h e r 2 0 2 0 r a n d o m i s e d t r i a l s s e r i o u s n o t s e r i o u s s e r i o u s n o t s e r i o u s a l l p l a u s i b l e r e s i d u a l c o n f o u n d i n g w o u l d s u g g e s t s p u r i o u s e f f e c t , w h i l e n o e f f e c t w a s o b s e r v e d 1 1 6 2 3 2 -0 ( 0 t o is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . e g y : --------------------------------------------------------------------------------1 R e s p i r a t o r y I n s u f f i c i e n c y / o r P n e u m o n i a , V i r a l / o r L u n g D i s e a s e s / o r R e s p i r a t o r y P r o t e c t i v e D e v i c e s / o r P r e s s u r e U l c e r / o r C o n t i n u o u s P o s i t i v e A i r w a y P r e s s u r e / o r H u m a n s / o r r e s p i r a t o r y d e v i c e s . m p . o r C o r o n a v i r u s I n f e c t i o n s / 2 M a s k s / o r m a s k s . m p . 3 1 o r 2 . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 17, 2020. . Contamination: a comparison of 2 personal protective systems Risk of self-contamination during doffing of personal protective equipment Selection and Use of Respiratory Protection by Healthcare Workers to Protect from Infectious Diseases in Hospital Settings Powered air-purifying respirator use in healthcare: Effects on thermal sensations and comfort Laboratory performance evaluation of N95 filtering facepiece respirators The impact of respiratory protective equipment on difficult airway management: a randomised, crossover, simulation study Respiratory protection during simulated emergency pediatric life support: a randomized, controlled, crossover study. Prehospital and disaster medicine Comparison of powered and conventional air-purifying respirators during simulated resuscitation of casualties contaminated with hazardous substances Effect of an Intervention Package and Teamwork Training to Prevent Healthcare Personnel Self-contamination During Personal Protective Equipment Doffing. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America CC-BY 4.0 International license It is made available under a