Access Now: AORN COVID-19 Clinical Support

Archive September 2020 XXI, No. 9

Infection Prevention: How Clean Is Your OR Air?

COVID-19 increases the importance of addressing airborne pathogens.

Stephanie Taylor

Stephanie Taylor, MD, M. Arch, CIC.


BREATHE EASY In the fight against COVID-19 and SSIs, making sure clean air circulates through ORs is just as important as robust surface disinfection.

As the COVID-19 pandemic continues, surgical facilities are grappling with the challenge of ensuring patients and staff don't contract the virus in their facilities. That's led to a lot of talk about surface disinfection, which is extremely important. But what about the place in which the aerosolized virus resides before it lands on a surface? What about the air itself? You need that to be clean, too. Like surface disinfection, the cleanliness of your facility's air is all about risk mitigation. It's something you should constantly monitor. Here's what you need to keep an eye on.

  • Relative humidity. For me, this is by far the most important aspect of preventing COVID-19, as well as surgical site infections (SSIs). The magical relative humidity zone for your entire building — the ORs, PACU, the lobby, the waiting room, the offices, you name it — is 40% to 60%. In terms of human health, we do best in that range. Why? Take the microbiome of your gut. We couldn't live without all those "good" organisms that reside in our body. It turns out that "good" microbes are most abundant, and "bad" ones — the pathogens — are least infectious in that midrange humidity zone.

Aim to humidify your entire building in that very comfortable range.

That sounds relatively straightforward, but it's sometimes easier said than done. Many surgeons like to keep their ORs cool because they're wearing multiple layers of sterile gowns, and in the COVID-19 era, maximum PPE usage is going to be even more commonplace. But when you turn the temperature down in the OR you could develop condensation in your ductwork because the dew point is reached. In response, facility managers often lowered the minimum relative humidity in ORs to 20%. When they did that, SSI rates increased. With low humidity, more infectious particles are in the air. That's been a big surprise to many surgical professionals, but findings have been very consistent in this regard.

With low humidity, more infectious particles are in the air.

There are so many other benefits to midrange humidity. The cells around a surgical incision are less likely to become damaged because the air isn't too dry. You're also supporting everyone's respiratory immunity — keeping the mucus in their airways hydrated, ensuring the cilia are able to function and facilitating production of interferon, a protective protein.

  • Air filtration. Filtering the air in your facility is more important than ever. I currently serve on the epidemic task force with the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). We recommend MERV 13 ­— middle-efficiency filtration — throughout the building and higher-efficiency HEPA filters in the ORs. One widespread, fearful notion about COVID-19 is that it can travel through your HVAC system. Well, yes and no. This novel coronavirus is a ribonucleic acid (RNA) virus. Viral RNA has been recovered from HVAC systems, but the jury remains out on how infectious it might be, as we still need more testing and study. Bottom line: High-efficiency HEPA filters in your ORs are important safeguards.
  • Air exchanges. ASHRAE recommends anywhere from 15 to 22 room air changes per hour for ORs. Note that changing the room air more frequently doesn't guarantee it will be clean, which gets us back to humidity. If the air is really dry and you have 30 air changes an hour, you'll actually have more particles in the air than if you have proper humidity and a lower air change rate. At 40% to 60% relative humidity, you can reduce your room air change rates and save energy that way, too.
  • Novel solutions. A number of technologies such as hydrogen peroxide vapor, aerosolized hydrogen peroxide and ultraviolet light (UVC) can assist you in keeping the air free of COVID-19 and other pathogens. In my view, they're all positive as supplemental tools to the regular manual cleaning of surfaces, but won't guarantee safety on their own. For example, engineers generally design laminar airflow into ORs. Traditionally, that means air comes down the walls. You're trying to avoid air turbulence, which stirs up infectious particles and dust that you don't want landing in your incision. The thing about laminar airflow is it never works as well as it does in computerized flow diagrams. Theoretically, it's a good idea, but it doesn't really work that precisely.

UVC can disassemble RNA viruses such as COVID-19. Although we usually think of UVC in terms of portable robots, I believe UVC has a use in ductwork, such as around cooling coils where you don't want biofilm forming. What's scary, however, is that we're beginning to see viruses and bacteria that have developed resistance to ultraviolet light.

Keeping your facility safe from COVID-19 is an ongoing process where numerous different components work together to minimize risk. You can't totally eliminate the possibility of there being COVID-19 in your building, but by employing all of the tools in your belt, you can make your environment as safe as it possibly can be. OSM

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