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Manoj Ramachandran

Manoj Ramachandran

Consultant Orthopaedic and Trauma Surgeon and Visiting Professor
Royal London and Barts and The London Children’s Hospitals,
Barts Health NHS Trust, London, England
@manojram1

Introduction

In these unprecedented times in the midst of the COVID-19 pandemic, where wearing masks has become a necessity to not only protect ourselves but also everyone in our vicinity or that we may come into contact with, it is important to know what the proper facial protection to wear is. 

I thought I would focus on what we wear on the frontline as senior surgeons (and why), why some masks in general use may not be so protective and what the advantages and disadvantages of each type of mask are. The information in this short article is aimed both at the public and at key workers in healthcare settings.

It’s worth starting by thinking about why we need protection. In a healthcare setting, there are multiple risks, including splashing of bodily fluids (e.g. blood and saliva) and airborne transmission of disease-causing pathogens such as bacteria and viruses. In the context of coronaviruses, the aim is to minimize the risk from airborne particles, which can either be aerosols or droplets. 

What is the difference between aerosols and droplets?

Aerosols are liquid or solid particles suspended in air and they can be visible (like fog) or invisible, which is most common. In fact, these invisible aerosols are what we know as small droplets, which, because of their size, are buoyant and float in the air for a long period of time before they evaporate. Therefore, they can float long distances and increase the risk of airborne transmission of disease. Large droplets tend to drop to the ground before they evaporate, therefore causing droplet transmission in a smaller radius. Also it’s worth remembering that large droplets turn into small droplets as they evaporate, so the distinction between the two is not crystal clear.

Note that we are particularly cautious of transmission in environments such as operating theatres because procedures involving anaesthetising patients and tubing their airways increases the risk of aerosol generation. The risk of this is much less outside of these environments, but remember that activities such as coughing and sneezing do result in aerosol generation.

How do I Choose The Correct Face mask?

Let’s move on to personal protective equipment (PPE) and specifically masks. It’s worth considering the 4 Fs that determine the effectiveness and ease of use of masks:

  1. Filtration: Consider how much filtration is needed. When in an environment where there is high droplet or aerosol transmission e.g. next to known COVID-19 infected patients, use a high filtration mask (see particulate filter respirators below).
  2. Fluid resistance: Use a fluid-resistant mask when there is any splashing of fluid from a known infected source. The reason why surgeons use surgical masks in an operating theatre is to protect against splashes. There are 3 grades of surgical masks available and we will look at each of these in turn later.
  3. Functionality: In surgical settings, we use level 3 surgical masks with hand ties. In addition, we may use anti-fog films and tapes to reduce fogging issues, and shields and additional eyewear to protect the eyes from blood and other fluid splashes.Washability, breathability and reusability are other features to consider.
  4. Fit: It is incredibly important that masks fit correctly. The nose and mouth must be completely covered and a tight seal created around the face to prevent gaps that increase the risk of exposure to droplets and aerosols.

Please do remember that we use masks in order to keep aerosols and droplets out of our respiratory tract (to protect ourselves) and to keep our own aerosols and droplets In (to protect others). In addition, don’t forget that we should always try to minimize the risk of contact spread by social distancing, hand hygiene and avoiding touching the mask or face.

The four categories of masks available are:

  1. Homemade non-manufactured face masks
  2. Manufactured non-medical grade face masks
  3. Surgical masks
  4. Particulate filter respirators
Homemade non-manufactured face masks

Homemade non-manufactured face masks

Let’s start with the most basic face coverings, the homemade non-manufactured face masks that are easy to put together e.g. using scarves, bandannas or handkerchiefs. To be honest, the level of protection here is negligible. Although it is probably better than nothing, clearly we would not wear these in a healthcare environment! In terms of droplet and aerosol transmission (which can contain coronavirus), the level of protection is minimal for the smallest droplets, although increasing the number of layers may be more effective. So when you are out and about in public, these face coverings are better than having nothing on but do be aware of their limitations. 

Manufactured non-medical grade face masks

Manufactured non-medical grade face masks

The next level of protection is from manufactured non-medical grade face masks (including homemade sewn converings). Again, to be clear, the level of protection against droplets and aerosols  is minimal and although they are used by the public frequently, remember again that social distancing, hand hygiene and avoiding touching the mask or face is much more important

Surgical masks

Next up are surgical masks  that are commonly used in healthcare settings, especially on the frontline. There are 3 types of surgical masks available:

When do healthcare workers wear Type I face masks?

Type I (Level 1): provide low barrier protection for use for low-risk, nonsurgical procedures and interactions at the frontline of healthcare where the wearer is not at any risk of fluid or droplet exposure. An ear loop mask that is readily available for purchase is considered a level 1 mask. These level 1 masks can be used when you are in contact with mild or asymptomatic suspected or confirmed cases of COVID-19 and if this is all that is available, consider using an additional full-face shield. Bacterial efficiency is in the region of 95% or greater. Type 1 masks are available in washable, breathable and reusable versions.  In the UK, these masks should comply with the EN14683:2019 Type I standard.

When do healthcare works wear Type II or Type IIR (FRSM) Face Masks?

Type II & IIR: provide moderate barrier protection where there are low-to-moderate levels of aerosols, sprays and fluids. An example of frontline healthcare use is when minimal exposure to droplets is likely to occur e.g. in emergency departments for wound dressings. Bacterial efficiency is in the region of 98% or greater. Type II are made up of a 3 ply construction while type IIR are slightly thicker with a fluid repellent layer. Note that the fluid resistant properties of Type IIR masks are specifically for close proximity environments such as care homes and hospitals and will protect against fluid transfer from coughs and sneezes. The World Health Organisation certifies Type IIR (and FFP2 masks) for use in close clinical environments e.g. in healthcare settings with known COVID-19 patients. In the UK, these masks should conform to the EN14683:2019 Type IIR standard.

What is a Level 3 Face Mask ?

Type III (Level 3): provide maximum barrier protection for any situation that has the potential for exposure to heavy levels of aerosols, sprays and fluids. These are the masks we use in all surgical and trauma procedures where there is a high risk of blood or body fluid splash. Bacterial efficiency is in the region of 98% or greater. In general, these masks should be reserved for use in operating theatres only and in trauma environments. Type IIR masks are more suitable for general use by the public.

Please do note that with surgical masks, the face seal is still loose fitting and leakage can occur around the mask as the wearer inhales and exhales. These masks do not provide the wearer with a reliable level of protection from inhaling small airborne particles and so cannot be considered to provide a high level of respiratory protection. Most importantly though, they generally stop the wearer from infecting the surrounding environment.

 

Particulate filter respirators

These masks are designed to provide the highest level of protection for the respiratory tract and are generally limited for use in healthcare settings. However, during the current pandemic, they have become available for use by the general public, especially as certified manufactures have increased their production capabilities globally

The most commonly available one is the N95, although N99 respirators are also available. The N stands for Non oil-based particles and the number (95 or 99) stands for the percentage of suspended particles (in the micrometer range) that the mask can filter out. Both are excellent at reducing the wearer’s exposure to airborne and droplet transmission. One other difference between N95 and N99 respirators is that N95s are a single standalone unit, while N99s have two separate components, a reusable respirator along with a disposable filter or valve (this is added because the filtration material of the respirator is thicker). Note that FFP stands for Filtering FacePiece and that FFP2s are equivalent to N95s and FFP3s to N99s.

When do healthcare workers wear an N95 (FFP2) Face Mask?

N95 (FFP2) respirators were designed to be used in healthcare settings where respiratory protective equipment is needed from high-risk particle generators such as aerosol generation in patients with highly infectious diseases (such as tuberculosis) and smoke generation from procedures (such as electrosurgical dissectors) and therefore, standard surgical masks should not be used.

Particulate filter respirators, in comparison to the other types of masks available, offer a much closer fit to the face but this can become uncomfortable over prolonged periods of wear. In high-risk healthcare settings, fit testing is essential to ensure that leakage is minimal during respiration.

N95 respirators are held in place by elastic ear loops or head straps and provide excellent protection. However, they cannot be shaped any further to your face for closer fitting and there is a maximum of 8% leakage to the inside.

When do healthcare workers wear an N99 (FFP3) Face Mask?

Following on N99 (FFP3) respirators, on the other hand, are better shaped to your face for a tighter fit (and so can be slightly more uncomfortable) and the additional valve does help make breathing easier.

N99 respirators only have a maximum leakage of 2% to the inside and the valve also reduces moisture buildup, allowing the mask to be worn for a longer period of time.

In general, N95 respirators give the most protection needed in high-risk healthcare settings, although we as surgeons do avoid the use of valves in operative cases as although the one-way valve filters the inhaled air, exhaled air is expelled out through the valve. 

Summary

This short article focuses on when frontline healthcare workers use certain types of masks and why. The information provided is also for general public use and I would recommend that you digest all the information available here (and other trusted sources) and make your own evidence-based decision as to which type of mask would be most suitable for you. Do remember though that in addition to wearing masks, social distancing, hand hygiene and avoiding touching the mask or face are of paramount importance.

*Please refer to HM Government Guidelines

 

 

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