Recently published field studies of HCWs managing patients with COVID-19 demonstrated equivalent rates of healthcare provider infection in cohorts utilizing PAPR versus other appropriate respiratory protection. We identified a trend towards lower level of cross-contamination in participants using PAPR technology compared to alternative respiratory protection in low quality simulation studies. We identified moderate quality of evidence towards improved healthcare worker comfort (heat tolerance and visibility) with PAPR technology compared with alternative respirators. PAPR users scored the technology lower with on mobility, dexterity, audibility and communication. We identified moderate quality of evidence towards improved healthcare worker comfort (audibility and mobility) with APR (airflow powered respirator) technology compared with PAPR.

There appears to be no reported difference in observed infection rates in participants utilizing PAPR or other appropriate respiratory protection. Preferred use of PAPR for respiratory protection may be due to perceived logistical advantages by institutional policy makers. A prospective international multicenter cohort study found no difference in infection rates between cohorts utilizing varied respiratory protection (50). A series published recently found no airway proceduralist infections in the cohort utilizing PAPR versus a cohort equipped with more routine respiratory protection in addition to usual PPE (41). This study was performed retrospectively in Wuhan during the outbreak of SARS-CoV-2. (41). Differences in the airway proceduralist’s COVID outcomes appear distinct: 10.7 % in the El-Boghdadly et al study versus 0% reported in Yao et al (50) (41). These findings may have been confounded by a well-designed enhanced respiratory and contact protective system in the study with no provider infections.

We observed a trend towards lower contamination rates in simulation studies in participants utilizing PAPR (42) (40). These observations are counterintuitive towards an assumption that due to complexity of technology, cross-contamination during doffing with PAPR is more likely. Results of our review demonstrate a trend towards lower HCW contamination rates and decreased doffing violations whilst utilizing PAPR.

We found no studies which assessed compliance with donning or doffing protocols for equipment utilizing PAPR.

In line with subjective reports that PAPR may be more effective in decreasing the effort needed to maintain the work of breathing compared to a more conventional filtering face piece, we identified moderate quality of evidence for this outcome (43) (7). We identified moderate quality of evidence towards improved healthcare worker comfort with regards to heat tolerance and visibility with PAPR technology. It is thought that through the positive air flow, PAPR’s eliminated the heat build up (52). Decrease in audibility and communication difficulties can be anticipated due to increased weight of the equipment and noise generated by positive airflow. In observational studies, we identified a trend toward greater level of self-reported comfort amongst the PAPR wearers (42, 44). Powell et al noted a lower temperature measurement in subjects using PAPR (43). Prior reports have outlined potential for claustrophobia in healthcare providers with field use of PAPR (53). During the tuberculosis outbreaks, use of PAPR’s had a low institutional uptake. This occurred due to a number of factors, including concerns that doctors would appear frightening to their patients and that the motor’s hissing noise would interfere with patient communication (54). Greater acceptance of PAPR by HCWS during both the SARS-Cov-1 pandemic and Ebola may be influenced by HCW perception of relative risk. Khoo et al published a survey illustrating that PAPR as opposed to N95 were more comfortable for HCWs during an Ebola outbreak in Singapore (55).

We identified no studies exploring the costs of resource use of PAPR versus any other filtration pieces. Costs of maintenance of PAPR equipment which require disinfection, cleaning, self-storage, battery maintenance as well as a requirement for education of significant proportion of HCW workforce have not been considered in evidence-based literature. These costs are juxtaposed against more wears per piece of PAPR compared to disposable face-filtering pieces. PAPR use may be a resource utilization prepared strategy for times of greater need for N95/FFP2. It has been noted that there have been fewer equipment shortages for PAPR than N95 (56).

We identified a single simulation randomized controlled trial which demonstrated a trend towards lower risk of contamination when PAPR use was incorporated with a teaching program. During the SARS-CoV-1 outbreak recent training in infection control increased the likelihood of workers adherence to recommended barrier precautions (57). Whilst the initial focus was on use of more stringent respiratory PPE components, further studies found that SARS -CoV-1 transmission was not supported if more standardized PPE was used. Critical system factors protecting the HCWs included compliance with N95 mask application and ongoing use, as well as complementary respiratory protection protocols (25).

Current reports of the choice of protective respiratory technology during the SARS-CoV-2 pandemic are disparate. In a recently published experience of intubation and ventilation of critically ill patients in Wuhan, Meng et al they illustrated use of a positive pressure ventilation system for anaesthesiologists dealing with COVID-19 positive patients (58). There have been three separate descriptive reports from Singapore on routine use of PAPR in their protocols for anaesthesia in suspected or confirmed Covid-19 patients (59) (60) (27). Recommendations from the Joint Task Force of the Chinese Society of Anesthesiology and the Chinese Association of Anesthesiologists center on N95 use for proceduralists. These recommendations do not specifically mention use of a PAPR device. Although some authors make recommendations for the use of PAPR for critical care of Covid-19 patients, they acknowledge that there is no conclusive evidence to show that this advanced respiratory technology decreases the likelihood of viral airborne transmission (61).

Utilization of PAPR with high filtration efficiency may represent an example of “precautionary principle” wherein action taken to reduce risk is guided by logistical advantages of PAPR system. With a higher APF factor than N95 masks, it is scientifically plausible that PAPR use may result in long term lower HCW infection rates. There is however limited literature supporting PAPR use during epidemics/pandemics of SARS-CoV-1, SARS-CoV-2, MERS and Ebola. Given the lack of demonstrable efficacy, institutional decision makers may be applying a pragmatic choice to use PAPR on the basis of precautionary principle.

Current PAPR certification standards have been developed primarily for industrial applications. There is a need for respirator standards to better expand to suit the requirements of healthcare workers (62). In terms of the laboratory research, industrial, radioactive or biological particles behave in a similar manner with regards to a filtration standard. Quantification of the infectious dose with this emerging viral disease has not occurred. Therefore, it remains a challenge to determine the optimum respiratory protection under individual circumstances. Future developments include adjusting the testing standards to activities to which the user (HCW) is engaged.

Our systematic review has been limited by a number of available studies graded as low evidence. A recently published study by El-Boghdadly et al had only 28.8% of laboratory confirmed infections. The remainder were diagnosed through self-isolation and hospitalization without confirmed laboratory testing. (50). In additi in the absence of phylogenetic analysis it is not possible to conclude the source of infection, be it patient contact or community acquired. Comparison of infection rates with HCWs not wearing the PAPR technology may be biased by other PPE protection factors such as the utility of system-related compliance measures (63). Despite the theoretical advantages of PAPR, there have to date been no controlled clinical trials on the efficacy of this technology during the SARS-Cov-1, SARS- Cov-2, EBOLA or MERS pandemics in comparison with other high level respiratory protection(64). At present, minimal infective dose for SARS-CoV-2 pathogen is unknown for any of the transmission modes (65). Higher viral load shedding may be more readily associated with greater disease severity (66). Whether a higher PAPR filtration factor translates to decreased infection rates of HCWs remains to be elucidated. True randomized controlled studies may not be ethically feasible due to higher filtration factor of PAPR. Pragmatic observational studies, as published recently in well-resourced areas may be both more ethical and feasible (41). Most of the studies included have been performed using simulation. Despite simulation being designed to simulate exposure to highly contagious diseases, they are performed in a safe setting without true haste (46). This may introduce systematic bias to the studies themselves and the review. We graded the risk of bias in observational on-field studies as high. This is due to a number of factors including the observational nature of SARS-CoV-2 infection rate assessment and potential for confounding due to attendant infection control processes.