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PPE--personal protective equipment. How we can have enough in the era of Covid-19.

We doctors are worrying about shortages of personal protective equipment. PPE is what we call it. When we see a patient with a disease that could be transmitted to others, we wear things that cover our bodies that can either be washed or thrown away. Infections can be spread by contact, by droplets or aerosols. We have different precautions for each type and within these categories, what we do depends on precisely which kind of infection we are worried about. We also, since the advent of HIV, use "universal precautions" to protect ourselves and our patients from bloodborne pathogens that we may have no reason to suspect but might be present anyway.

Universal precautions include wearing gloves for any procedure that involves contact with a patient's blood or body fluids or presents a significant risk for that, such as drawing blood or cleaning wounds.

Diseases such as influenza or certain pneumonias are transmitted by droplets. For those infections we need to use a mask and ideally the patient will use one too. Contact precautions, requiring the use of gowns and gloves, cleaning equipment we use on the patient before re-use, is for things like infectious gastroenteritis (stomach flu, norovirus), Clostridium difficile and resistant bacterial infections such as MRSA. Airborne precautions are for diseases such as tuberculosis, measles and chickenpox. Those require a mask that filters out most particles. The N95 mask filters out 95% of airborne particles. The N stands for "not" oil resistant since these masks are also used for industrial particle protection. We also use a helmet type device called a PAPR or powered air purifying respirator. This has a little battery powered HEPA filter that creates airflow inside a plastic shield that hangs off of a well fitting lightweight helmet.

Covid19 is carried by droplets but viruses also can move as an aerosol. The arosolized viruses can float further than a droplet and when the virus lands it is viable for hours to days. Protection in this case includes droplet, aerosol and contact precautions. So that means we should use a gown, gloves and a mask at least as good as an N-95. N-95 masks work if they have been fitted to a person's face and don't allow air around the sides. When I was fitted for my N-95 mask, a skilled occupational medicine nurse at my hospital found the right size and showed me how to put it on. She then put a hood over my masked head and sprayed a few small but pungent particle sprays in the hood to see if I could taste or smell them. The small size mask fit me well so that is the size I wear. Nobody in my clinic that I know of has been fitted for N-95 masks and we don't have any in my clinic anyway. We use the much more common surgical mask that is only effective for droplet transmission or a PAPR for very high risk patients. We also use gloves and disposable gowns. All masks and gowns and perhaps gloves are available only in the numbers that we normally use, so we're going to run out in places with a high volume of visits. We will run out even in places where Covid19 doesn't overrun us because we will be using them, appropriately, for everyone we suspect of having it.

The good news is that the virus causing Covid19 does not live forever on dry surfaces. A group of researchers in Hamilton, Montana looked at the survival of virus on various dry surfaces and found that it survives best on metal and plastic, up to 72 hours, but less well on copper or cardboard. This means that it would be possible to "quarantine" our masks and gowns for some number of days and re-use them in rotation. This would be especially safe in equipment we used just to be super safe around a person with a cough or sore throat who turned out to be very unlikely to have Covid19. If we put the (not grossly soiled) PPE in a bag with a date on it we could be quite sure that it would be safe to re-use after 5 days. This will not help the hospitals already at the end of their supplies. There will also be attrition of PPE as it gets ratty, torn, soiled or breaks. We still need all of the ideas for increasing supply of this stuff, especially to the hardest hit areas of the country.

Be aware, though, that the longer the virus is away from the host, the less infectious it will be. This applies to our home situations as well. Right after being sick with this virus our homes will have viable virus around. When we are well, however, it won't take long for the virus in our environment to be well and truly gone. Cleaning and disinfecting may be a good idea but once people in the home are well and immune it won't be strictly necessary.

Making masks out of cloth is probably not terribly useful except in situations of dire need since it would be very difficult to make a mask that was able to protect against aerosols. But droplet protection is better than nothing, especially for people working outside of healthcare. I saw a hilarious and probably effective mask from Tbilisi, Georgia, on a guy in a bus. It was a 5 gallon water bottle with the bottom cut off, attached to a sweater, with a baffle at the neck of the bottle which was at the top. Not attractive, certainly, but most likely very effective. Also encourages social distancing!

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