Quel pourcentage d'efficacité de ton masque?

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double l'efficacité de ton masque

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Evaluation of Cloth Masks and Modified Procedure Masks as Personal Protective Equipment for the Public During the COVID-19 Pandemic
Phillip W. Clapp, JAMA Intern Med. Published online December 10, 2020.

Question What are the fitted filtration efficiencies (FFEs) of consumer-grade masks, improvised face coverings, and modified procedure masks commonly used during the coronavirus disease 2019 (COVID-19) pandemic?

Findings In this comparative study of face covering FFEs, we observed that consumer-grade masks and improvised face coverings varied widely, ranging from 26.5% to 79.0% FFE. Modifications intended to enhance the fit of medical procedure masks improved FFE measurements from 38.5% (unmodified mask) to as much as 80.2%.

Meaning Simple modifications can improve the fit and filtration efficiency of medical procedure masks; however, the practical effectiveness of consumer-grade masks available to the public is, in many cases, comparable with or better than their non-N95 respirator medical mask counterparts.

Abstract
Importance During the coronavirus disease 2019 (COVID-19) pandemic, the general public has been advised to wear masks or improvised face coverings to limit transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, there has been considerable confusion and disagreement regarding the degree to which masks protect the wearer from airborne particles.

Objectives To evaluate the fitted filtration efficiency (FFE) of various consumer-grade and improvised face masks, as well as several popular modifications of medical procedure masks that are intended to improve mask fit or comfort.

Design, Setting, and Participants For this study conducted in a research laboratory between June and August 2020, 7 consumer-grade masks and 5 medical procedure mask modifications were fitted on an adult male volunteer, and FFE measurements were collected during a series of repeated movements of the torso, head, and facial muscles as outlined by the US Occupational Safety and Health Administration Quantitative Fit Testing Protocol. The consumer-grade masks tested included (1) a 2-layer woven nylon mask with ear loops that was tested with an optional aluminum nose bridge and nonwoven filter insert in place, (2) a cotton bandana folded diagonally once (ie, “bandit” style) or in a (3) multilayer rectangle according to the instructions presented by the US Surgeon General, (4) a single-layer woven polyester/nylon mask with ties, (5) a nonwoven polypropylene mask with fixed ear loops, (6) a single-layer woven polyester gaiter/neck cover balaclava bandana, and (7) a 3-layer woven cotton mask with ear loops. Medical procedure mask modifications included (1) tying the mask’s ear loops and tucking in the side pleats, (2) fastening ear loops behind the head with 3-dimensional–printed ear guards, (3) fastening ear loops behind the head with a claw-type hair clip, (4) enhancing the mask/face seal with rubber bands over the mask, and (5) enhancing the mask/face seal with a band of nylon hosiery over the fitted mask.

Main Outcomes and Measures The primary study outcome was the measured FFE of common consumer-grade and improvised face masks, as well as several popular modifications of medical procedure masks.

Results The mean (SD) FFE of consumer grade masks tested on 1 adult male with no beard ranged from 79.0% (4.3%) to 26.5% (10.5%), with the 2-layer woven nylon mask having the highest FFE. Unmodified medical procedure masks with ear loops had a mean (SD) FFE of 38.5% (11.2%). All modifications evaluated in this study increased procedure mask FFE (range [SD], 60.3% [11.1%] to 80.2% [3.1%]), with a nylon hosiery sleeve placed over the procedure mask producing the greatest improvement.

Conclusions and Relevance While modifications to improve medical procedure mask fit can enhance the filtering capability and reduce inhalation of airborne particles, this study demonstrates that the FFEs of consumer-grade masks available to the public are, in many cases, nearly equivalent to or better than their non-N95 respirator medical mask counterparts.

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Another Explanation for Why Cloth Masks Reduce COVID-19 Severity
Rita Rubin, MA JAMA. 2021;325(12):1134.
It’s not just the mask, it’s the humidity created inside the mask that helps protect against severe COVID-19, a recent study by National Institutes of Health (NIH) researchers suggests.

The use of cloth masks has been linked with decreased disease severity, which is surprising considering such masks aren’t good at filtering out the smallest aerosol particles that can reach the lower respiratory tract, the researchers wrote.

They tested 4 types of masks: an N95 respirator, a 3-ply disposable surgical mask, a 2-ply cotton-polyester mask, and a heavy cotton mask. Volunteers breathed into a sealed steel box, and the scientists then measured the humidity level inside it.

With no mask, the water vapor of exhaled breath filled the box, increasing humidity. But when the volunteers wore any of the 4 types of masks, humidity levels in the box declined because the masks trapped most of the water vapor in their exhaled breath. The researchers noted that the volunteers’ faces fit tightly against high-density foam rubber surrounding the opening in the box, eliminating leakage around the masks’ edges.

Increased humidity of inhaled air hydrates the respiratory epithelium, which is known to benefit the immune system. It also promotes the removal of mucus, and potentially harmful particles within it, from the lungs. High humidity can also enhance production of interferons that fight viruses.

“High levels of humidity have been shown to mitigate severity of the flu, and it may be applicable to severity of COVID-19 through a similar mechanism,” coauthor Adriaan Bax, PhD, a biophysicist at the National Institute of Diabetes and Digestive and Kidney Diseases, said in a statement.

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Traduction de l'étude

Une autre explication de la raison pour laquelle les masques en tissu réduisent la gravité du COVID-19
Rita Rubin, MA JAMA. 2021; 325 (12): 1134.
Ce n’est pas seulement le masque, c’est l’humidité créée à l’intérieur du masque qui aide à se protéger contre les graves COVID-19, selon une étude récente des chercheurs des National Institutes of Health (NIH).

L'utilisation de masques en tissu a été associée à une diminution de la gravité de la maladie, ce qui est surprenant étant donné que ces masques ne sont pas bons pour filtrer les plus petites particules d'aérosol pouvant atteindre les voies respiratoires inférieures, ont écrit les chercheurs.

Ils ont testé 4 types de masques: un respirateur N95, un masque chirurgical jetable à 3 couches, un masque en coton-polyester à 2 couches et un masque en coton épais. Des volontaires ont respiré dans une boîte en acier scellée, et les scientifiques ont ensuite mesuré le niveau d'humidité à l'intérieur.

Sans masque, la vapeur d'eau de l'haleine expirée remplit la boîte, augmentant l'humidité. Mais lorsque les volontaires portaient l'un des 4 types de masques, les niveaux d'humidité dans la boîte diminuaient car les masques emprisonnaient la majeure partie de la vapeur d'eau dans leur souffle expiré. Les chercheurs ont noté que les visages des volontaires s'adaptent étroitement au caoutchouc mousse haute densité entourant l'ouverture dans la boîte, éliminant les fuites autour des bords des masques.

L'augmentation de l'humidité de l'air inhalé hydrate l'épithélium respiratoire, qui est connu pour être bénéfique pour le système immunitaire. Il favorise également l'élimination du mucus et des particules potentiellement nocives à l'intérieur des poumons. Une humidité élevée peut également améliorer la production d'interférons qui combattent les virus.

«Il a été démontré que des niveaux élevés d'humidité atténuent la gravité de la grippe et peuvent s'appliquer à la gravité du COVID-19 grâce à un mécanisme similaire», co-auteur Adriaan Bax, PhD, biophysicien à l'Institut national du diabète et de l'appareil digestif et rénal Maladies, a déclaré dans un communiqué.