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Rethinking air pressure in operating rooms could save lives

July 29, 2022

By Tariq Amlani

Airborne infection prevention requires investigation of new approaches and codes

People are at their most vulnerable in the operating room. And the pandemic experience has shed new light on what's been a constant challenge, the engineering and design of operating rooms (ORs) that reduce hospital-acquired (or healthcare-acquired) infections (HAIs). Typically, ORs have been protected with positive air pressure. They are designed to shield the surgical site from infection from outside. And the air that systems push into the OR is typically HEPA-filtered and extremely clean.

As I’ve previously written, HAIs are a major issue. In 2018, the US Centers for Disease Control and Prevention (CDC) identified that nearly 1.7 million hospitalized patients in the US annually acquire HAIs while being treated for other health issues and that roughly 99,000 infected patients die due to these issues.

In Canada, a 2013 study indicated that more than 200,000 patients get infections every year while receiving healthcare; and 8,000 die as a result. Prior to the pandemic, the CDC recorded the US making progress in reducing HAIs. Due to the pandemic, requests are now coming in from clinicians for alternative configurations for ORs so that they can treat COVID-positive patients and not risk spreading the infection to adjacent operating rooms. 

Hospital-acquired infections can be deadly. Looking at air pressure in operating rooms may be key to reducing risks.

From an engineering and design perspective, I wonder if there is a better approach that can help reduce HAIs and save lives? Do we need, for example, both positive and negative-pressure ORs?

Why we use positive pressure in ORs

First, let us remember why we use positive air pressure in surgery. Surgery means breaking the body’s protective barrier to infection, bacteria, and fungi. With the body so vulnerable, conventionally we circulate huge amounts of clean air though the operating suite with a cascade of transferred air from the sterile core into the OR and from the OR into the surrounding racetrack. Positively pressured rooms prevent particles from adjacent areas from entering the operating rooms.

Operating on infectious patients

In the early months of the pandemic, we began to see the limitations of the positive air pressure OR. For instance, surgeons performing surgery on COVID-positive patients faced a conundrum regarding infection control. Keep the OR positive, bring in the patient and risk the release of viral particles into the OR and potentially to the other suites, racetrack, and to other patients in this area? Or make the OR negative pressure to protect patients in adjacent areas, which would also allow microbes and bacteria into the surgical suite?

These are difficult questions with no easy answers.

MERS example

We can learn from previous global outbreaks by looking at the ways surgeons around the world faced similar issues. In 2015, hospitals in South Korea did several things differently to adjust to the new infection risk presented by the MERS outbreak.

 They made some ORs negative pressure and some ORs positive pressure. They brought anterooms in. And they tried a variety of approaches that they hoped would allow them to accommodate infected patients while mitigating risk to staff and those in recovery. Post-op, they studied patient outcomes to see what worked best. They concluded that in the spaces converted to negative pressure and provided with an anteroom, operations were “performed without specific adverse events or perioperative MERS transmission.”

Our design and engineering can potentially save lives. But right now, the codes are stale. There are limited provisions in the codes that allows us to design a negative-pressure OR.

Three principles to keep in mind

For another perspective, I reached out to our global health sector studio. My colleague Patrick Chambers tells me that negative-pressure ORs are a hot topic in Australia, as well. He’s even drafted a plan to ensure that the negative-pressure theatre can achieve the same three basic principles that ultra clean air or ultra clean ventilation positive air systems provide.

These three principles are:

  1. Ensuring that floor particles are not disturbed and can’t come in contact with the open wound on the surgical table.
  2. Extracting the particles that originate above the wound from doctors/surgeons/nurses at low level and preventing recirculation at the surgical table.
  3. Ensuring that particles originating from outside the protected zone do not drift into the area of the surgical table/wound site. 

More examples

In other places we see hospitals using their intervention room as an anteroom and creating positive pressure there. Others are using pop-up anterooms with HEPA filters. We have also observed institutions deployment of mobile negative air pressure in response to COVID with some success.

Two conventional positively pressured operating room setups.

Opportunities for new research

Today, in new construction projects we are increasingly asked for the ability to design ORs for airborne infections. That means our clients want ORs designed with the ability to go negative pressure and have an anteroom to control infection. Our design and engineering can potentially save lives.

But right now, the codes are stale. There are limited provisions in the codes that allows us to design a negative-pressure OR. To allow for these new approaches, we need fundamental updates to our health codes. We should be asking questions such as where did the prescriptive air change requirements come from? “This is how it has always been done” is not a satisfactory answer. Do we need to build non-code compliant ORs to showcase innovative thinking and demonstrate that they are safe and can reduce infection?

Two potential operating room setups. One is a positively pressured OR with negatively pressured ante/setup rooms. The other is negatively pressured OR with positively pressured ante/setup rooms.

With data from the pandemic as well as examples of cleanrooms from the semiconductor and pharmaceutical industry in mind, there are rumblings of an industry conversation about changes to standards. We’re hearing calls for the industry to take a new look at aerobiological standards for healthcare spaces and update the guidelines to include standards for air quality. Can we apply a demand control style solution, with in-situ and live measurements of the actual number of colony-forming units in the space? Can we create prescriptive standards for airborne isolation operating rooms?

While we are examining air pressure in infection control, we must further investigate the relationship between ventilation rates, infection control, and energy consumption in healthcare settings in general. Are we getting the infection control benefit that justifies this level of energy consumption?

Some want the industry to take a new look at aerobiological standards for healthcare spaces and update the guidelines to include standards for air quality.

Conversation is underway

In this article, my colleague Paulina Czajkowski and I joined the conversation about the opportunities, needs, and impediments to change in hospital spaces and systems—negative-pressure OR spaces included. We need to continue to stimulate discussion about evidence-based solutions for hospitals and operating rooms especially regarding infection control.

It’s time to refresh the evidence, update the codes and time for hospital systems to consider investment that can mitigate infection and save lives. We believe anyone who has concerns regarding the air quality and infection prevention in our ORs will be interested in this operating room/cleanroom conversation and where it leads. 

  • Tariq Amlani

    A mechanical engineer and health sector leader, Tariq has extensive knowledge and experience working on the procurement, design, and construction of new and existing healthcare facilities.

    Contact Tariq
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