Informed decisions
Last Friday my column drew from an article in the Journal of the American Medical Association (JAMA) recommending that face shields — usually part of hospital personal protective equipment or PPE—be promoted for community use to fight COVID-19. The three authors — physicians from the University of Iowa — noted there were many advantages that face shields had over masks.
A reader, E. J. Buenaventura, wrote in to ask if perhaps I should qualify the advantage as being one over cloth masks specifically.
I promised another article to clarify matters, and thought this would be an excellent opportunity to show how we need access to facts and an understanding of a bigger picture of risk to make informed decisions around prevention.
We could start with the intrinsic efficacy of these face coverings, from lowest to highest: cloth masks, surgical masks, and N95 masks (so called because they filter 95 percent of airborne particles), and, finally, N95 respirators. (Respirators have to have a tight fit, while masks are more loose.) Face shields actually rate high in internal efficacy but are more often used in hospitals, in combination with the other coverings.
But wait, within each category there will be variations, like cloth masks that are improvised versus cloth masks that use a pattern prescribed by health experts. The efficacy depends as well on the type of fabric, cotton being the best.
Efficacy can be so complex. For example, the other day at a supermarket, I saw someone in the queue with double facial protection, but what happened was he lifted his face shield and took down the mask under the shield to scratch his nose.
He probably wasn’t aware of the risk of autoinoculation, which happens when your hands pick up the virus, maybe from a flat surface that an infected person coughed into, and then, by scratching your nose, you deliver the virus straight into your body. So much for the mask and shield.
Let’s run through the coverings again to get the advantages and disadvantages of each of them:
Cloth masks. Advantages: They do block the virus, with efficacy determined by the material, the way they are sewn and the way they are worn. Reusable. More useful to prevent the wearer from infecting others than the other way around. Disadvantages: Some difficulty breathing (I bought a “waterproof” one from the sidewalk, and you could hardly breathe with it), and the loose fit means your breathing ends up fogging eyeglasses. Do not protect the eyes. Hard to talk through the mask. Strong tendency for autoinoculation from adjusting the mask with dirty hands, to scratching an itch on the face. Also dangers from reusing the masks without washing.
“Surgical” masks. Advantage: Generally better at blocking the virus than the cloth masks. Disadvantages: All the ones stated for cloth masks, plus not being reusable.
N95 masks and respirators. Advantage: Very high efficacy in blocking virus. Disadvantages: Those mentioned for cloth masks. Packaging for N95 from the United States actually warns against prolonged use. It is so effective in keeping out viruses and tiny particles that it also reduces oxygen intake, even as toxic carbon dioxide, which you’re supposed to breathe out, accumulates inside the mask.
Face shields. Advantages: The plastic or acetate shield totally blocks the virus. Easier to breathe. Generally more comfortable than masks. Protects nose, mouth and eyes. Easier to talk, and people see your entire face (which sometimes can be a disadvantage, too). Easy to wash and reuse. Disadvantage: You might forget to wash; remember the virus can’t get through but can live on the plastic for up to three days, probably shorter in the real world but you have to be conscious not to autoinoculate.
Your choice will depend on the environment. No protective covering would be needed at home with people you’ve been quarantined with for six weeks now. If you have many visitors (strictly speaking, not allowed under the quarantine), and when you go out, a cloth mask helps, a surgical mask is even better. N95 might be OA (overacting).
And yet, if you have to care for someone with COVID-19 at home, then a surgical mask and a face shield for both the patient and caregiver would be appropriate when you are together at a close distance.
Oh, Philippine Airlines has announced it will resume some flights next week, requiring masks on passengers and PPE—masks with face shields—for flight attendants.
In all this, physical distancing still makes an important difference. Make it hard for the virus to even get to you, whatever you might be wearing. At another level, frequent hand-washing AND washing the cloth masks and face shields are also crucial.
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