Monaz: Hello, I'm Monaz Mehta, editor in the Cochrane Editorial and Methods department. Coronavirus disease 2019, or COVID-19, has spread quickly throughout the world, and we are updating the most relevant Cochrane reviews, as well as preparing rapid reviews of new topics. In this podcast, we asked author Blair Rajamäki from the University of Eastern Finland in Kuopio to describe the findings of the April 2020 update on the effects of personal protective equipment for healthcare workers.

Blair: COVID-19 has once again revealed that healthcare workers are at much greater risk of infection than the general population, because of their exposure to contaminated body fluids from patients. This was also seen during the Ebola and SARS epidemics, when high numbers of healthcare workers became infected and died.
Healthcare workers may become infected when splashes or droplets land on their eyes, mouth or nose or when these come into contact with contaminated skin. When working closely with patients with COVID-19, the only way to reduce their risk of infection is for healthcare workers to use personal protective equipment, known as PPE, which covers otherwise exposed body parts. This is not as simple as just wearing a mask, but requires the covering of all appropriate parts of the body.However, it’s unclear which type of PPE protects best, what’s the best way to put on the PPE (also called donning) or take it off (also called doffing), and how to best train healthcare workers to use PPE as instructed. We did our review to try to answers these questions.
We included all controlled studies of full-body PPE used by healthcare workers exposed to highly infectious diseases, such as Ebola, SARS or COVID-19. We measured effectiveness in three ways: infection, contamination and noncompliance with protocols. Because real-life studies can be difficult to conduct, we also included research that used fluorescent markers or a harmless virus or bacteria to simulate transmission of fluids containing the virus.
After searching several databases, we identified 22 simulation studies and 2 field studies, with altogether 2278 participants. Fourteen were randomised trials, and, overall, we have 8 studies comparing different types of PPE, 6 studies of various modifications of PPE design, 8 studies assessing donning and doffing techniques and 3 of training methods. In the simulation studies, contamination rates varied across all types of PPE, but more than 25% of participants were contaminated in more than half of the studies. 
For the comparison of different types of PPE, we had four main findings. First, using a powered air-purifying respirator with coverall protected better than a N95 respirator and gown, but it was more difficult to don. Second, those with a long gown had less contamination than those with a coverall and coveralls were more difficult to doff. Third, people with gowns had fewer spots of contamination than those with aprons. And, fourth, PPE made of more breathable material led to a similar number of spots on the trunk compared to a more water repellent material, but may have greater user satisfaction.
For modifications to PPE design, we found that sealed gown and glove combination; a gown that fits better around the neck, wrists and hands; a better cover of the gown-wrist interface; and added tabs to grab to facilitate doffing of masks or gloves all reduced contamination compared to standard PPE.
Turning to the methods of donning and doffing, we found some important benefits. Following the CDC recommendations for doffing may lead to less contamination compared to no guidance. Removing gloves and gown in a single step may be better than separate removal, and the same was true for using two pairs of gloves and removing the first pair at the start of doffing. Being given spoken instruction while donning and doffing may lead to fewer errors and less contamination spots. And, lastly, using quaternary ammonium or bleach to sanitize gloves before doffing may also decrease contamination but alcohol-based hand rub did not work as well.
Finally, the three studies of training showed that more active training, such as face-to-face instruction or computer simulation, was better than written instructions alone. 
In summary, our review shows that covering more parts of the body leads to better protection but usually comes at the cost of more difficult donning or doffing and less user comfort, which can actually lead to poor compliance and more contamination. This needs further research and we need better and larger simulation studies to find out which combinations of PPE protects best, the safest way to remove PPE and how to improve compliance. We also need more real-life evidence. The best way to do this during an epidemic is to organize a randomised trial but, when this is not possible, a good alternative is to register the use of PPE of exposed healthcare workers and then to follow them up to see who becomes infected.”

Monaz: If you would like to find out more about the effects of the different types of personal protective equipment, the full details are in the review, which is free online. Just go to Cochrane Library dot come and search 'ppe and healthcare staff'.