Masks for medical use

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Masks for medical use

The SARS-CoV-2 pandemic period we are currently living through shows a cruel lack of masks to protect oneself.

This is an opportunity for us to review respiratory masks: the different types of masks? for whom? for what use? how to use them?

That’s as many questions we’re going to try to answer.

What is this all about?

Masks are respiratory protection. They protect the respiratory tract from inhaling polluted air when one is in a place exposed to dangerous environmental factors such as dust (work…), solvents (paint…), aerosols or gases, biological particles…

We will not deal here with gas filtration, which requires special filters (A2P2 mask for paints or varnishes, toxic gases hood) or specific cartridges.

What is important to us now is to protect ourselves against the SARS-CoV-2 coronavirus, which is responsible for a terrible pandemic that is not unprecedented, as our history is marked by similar phenomena. These include plague epidemics, including the Black Death, which began in 1348 and caused 50 million deaths, killing almost half of the European population; influenza epidemics, including the Spanish flu, which in the years 1918-1919 killed between 20 and 50 million people, or between 2.5 and 5% of the world’s population; cholera epidemics…

The SARS-CoV-2 virus responsible for Covid-19 disease is transmitted primarily through droplets and respiratory secretions of patients that contaminate the air and surfaces. To prevent transmission of the disease, droplets (larger than 5 µm in size) of saliva, emitted by coughing, sneezing or simply speaking, must be prevented from dispersing into the air. When the droplets are smaller than 5 µm in size they are said to form an aerosol and are airborne and will directly contaminate the airways of the hosts who inhale them. This aerosol route does not appear to exist in the case of Covid-19.

The droplets fall on surfaces and it is therefore very important to wash your hands. In fact, as when we frequently touch our hands to our face, we contaminate our nose or mouth, which are entry points for the virus. Note that the virus can also enter through the eyes.

The most basic protection therefore seems to be wearing a mask.

The different masks

There are 2 very different types of masks: surgical masks and respiratory protection masks.

1-the surgical mask

It is also called care mask or medical mask. Originally it is made so that a surgeon equipped with it does not contaminate the operating field with his respiratory droplets. Its main purpose is to trap the droplets of saliva when the wearer exhales. Carried by the caregiver it prevents contamination of the patient and his environment (air, surfaces, products), carried by the contagious patient it prevents contamination of his surroundings and environment. To a certain extent it also protects the wearer against the risk of biological liquid splashes when it has an impermeable outer layer. For optimum protection, protective glasses or a protective screen should be used. When, as in the case of Covid-19, the infection is mainly transmitted by droplets, this mask, if it has an impermeable layer, acts as a “droplet” protection.

The surgical mask is a class 1 medical device and its regulation therefore depends on the ANSM (Agence Nationale de Sécurité du Médicament).

Bacterial filtration efficiency (BFE) is measured from the inside to the outside (in the direction of expiration). According to the EN 14683 standard, in vitro tests carried out with 3 µm bacteria distinguish 2 types: type 1 EFB > 95% and type 2 EFB > 98%. The mask can also be tested for its resistance to projection and can be noted R in the case of a positive result: e.g. type 2R.

Surgical mask

2- the respiratory protection mask

Its purpose is to protect the wearer from inhalation of airborne infectious agents, but it also protects against droplet transmission. It is classified as PPE (Personal Protective Equipment) and therefore depends on the Ministry of Labour. Contrary to the previous one, it is tested from the outside to the inside (direction of inspiration). The EN 149+A1 standard (September 2009) defines 3 classes of disposable respiratory protective equipment: FFP1, FFP2, FFP3 (Filtering Facepieces Particles). The standard takes into account filtration capacities and leakage to the face.

The ability to filter particles and the measurement of the inward leakage rate are therefore measured. This measures the ratio of the amount of contaminant that has passed through the interior of the mask to that which is on the outside.

Total inward leakage = (contaminant indoors)/(contaminant outdoors)

This leakage rate takes into account the direct passage of the non-retained contaminant through the filter and through the face seals.

For the biological protection we will retain mainly the 2 types, FFP2 which is declined in three forms: duck beak – folded – shell, and FFP3.

  • FFP2: It filters at least 94% of particles (0.6 µm aerosol) for a leakage rate of 8% or less. It is the reference protection in the event of a pandemic. It provides effective protection against bacteria and viruses. They are fitted with a white or blue elastic band.
FFP2 Mask with Valve
  • FFP3: It filters 99% of the particles for a leakage rate less than or equal to 2%.

It is also able to retain pollens and very fine particles such as radioactive dust. The elastic band is red in colour.

It is better understood why surgical masks are insufficient to protect people during an epidemic: despite their high filtration capacity (> 95 or > 98%) their tightness at the face is not evaluated. Very few studies have been carried out in this respect, total leaks are generally evaluated between 42% and 100%!

Utilization

We saw that the masks had different properties and therefore different uses. But for a real effectiveness it is important to use them properly.

In the case of FFP masks, the mask should be positioned so that it covers the mouth and nose, place the elastics, tighten the nose clip and fit the mask snugly under the chin. Once properly fitted, seal the perimeter of the filtering surface with your hands and inhale slowly and deeply. If the mask tends to collapse, there is no leak. The mask must be used for the time specified in the instructions for use and must be removed last when undressing. It should be removed in the DASRI before washing hands.

It should be remembered that these FFP masks protect against biological agents but not against gases and vapours.

Some masks, especially the FFP3, are equipped with an exhalation valve that allows you to exhale more comfortably.

Conclusion

As with any protective element, it is important to be familiar with the characteristics and uses of masks in the event of an outbreak.

The surgical mask prevents projections from inside to outside. Wearing it is altruistic behaviour.

Respiratory protection masks, FFP2 or even FFP3, are very effective in protecting against both droplet and aerosol risks, but only if they are correctly positioned and removed.

Nevertheless, the current shortage poses a significant problem, not only for the population but also for front-line health professionals. Imagine if the entire population wore a mask, even a surgical mask, with each individual protecting his or her neighbour, the transmission of the virus would be significantly slowed down. Everyone participates in the collective interest.

In any case, it seems to be one of the elements of South Korea’s success against the Covid-19: the very large number of screenings made it possible to quickly locate carrier and contact subjects. In addition, the wearing of masks, generalised to the entire population, has undoubtedly reduced the circulation of the virus, but this is a cultural problem.

A final point for reflection: in spending time with the elderly, the not-so-elderly and also with many caregivers, I realized that, for them, wearing a mask represents a very important psychological safety element.

Ouvry starts making masks. The company has the skills, the intelligence, lacks the experience that will follow very quickly.

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