What’s Lurking in the OR Air?

Surgical teams take great care in cleaning surfaces, prepping the patient’s skin and making sure barrier protection is in place to reduce the risks of surgical site infections (SSIs). That might not be enough to address what’s wafting in the air around them. HVAC systems and laminar flow are designed to limit the amount of dust, lint and skin shedding in the OR, but these particles still contribute to SSIs, according to a study published in the journal Surgery.

The study’s authors say the accepted standard on the ventilation of ORs requires a minimum of 20 air changes per hour with a minimum of four outdoor air exchanges. They point out that externally sourced air can introduce microbial and chemical contaminates to the OR and say recirculated air typically has higher levels of biological and chemical contaminants than external air. 

Healthcare-acquired infection (HAIs) are categorized into 13 major types with SSIs being among the most prevalent, according to the study, which says 70% of the pathogens responsible for SSIs are potentially airborne and difficult to address through traditional infection control practices. “Although it has been historically accepted that pathogens responsible for HAIs originate primarily from surfaces, recent literature indicates that airborne microbial burden constitutes a significant portion of the overall pathogens responsible for HAIs,” notes the study.

“It’s important to note that even properly gowned healthcare workers and patients have been documented to shed between 3,000 and 50,000 microorganisms per minute and an estimated 10% of the microorganisms shed have the potential to be infectious,” write the authors.

Based on these factors, the standard OR would surpass the recommended microbial load in as little as 10 minutes, according to the study. “The very nature of an OR with many air changes per hour, laminar flow and constant personnel movement facilitates airborne pathogen sustainment,” the authors write.

Healthcare facilities often employ high-efficiency particulate air (HEPA) filters to remove particulates and reduce the levels of biological contamination, notes the study. “Because HEPA devices are designed to capture particulates, any retained particulates are likely to remain inside the filter and the viable matter — bacteria, viruses, mold and fungi — may continue to grow and multiply,” notes the study. “The force from sustained high air velocities across the filter can cause previously entrapped particulates to separate, allowing them to enter the room.”

Charles Edmiston, PhD, emeritus professor at the Medical College of Wisconsin in Milwaukee, says there is an increasing body of evidence that shows airborne microbials can contaminate surgical wounds and cause SSIs. He says his own research has shown the presence of gram-positive bacteria in the air within one meter of surgical incisions, even with optimal laminar flow and regular air exchanges. 

Clearly, you should consider taking additional precautions to purify the OR air. “Portable units positioned next to the surgical table direct a sterile airflow across patients and instruments, creating a sterile barrier over the surgical wound,” says Dr. Edmiston.

Robert Osher, MD, a professor of ophthalmology at the University of Cincinnati and medical director emeritus of the Cincinnati Eye Institute, has been using such a device since 2017. “I won’t perform surgery without it,” says Dr. Osher. “I use it in every one of my cases, and it gives me a great sense of security. It makes me feel that I’m creating the safest possible field in which to perform surgery.”

Dr. Osher was involved in two studies focused on particles floating in the air of ORs. One study found particulate matter ranging in size from .5 to 5 microns, and the second discovered that a mobile sterile air unit positioned next to the sterile field significantly reduced particle size and the number of lint fibers falling into the field during cataract surgery.

Dr. Edmiston also points to the effectiveness of systems integrated into ceiling lights that provide continuous air purification by pulling air into the unit, where it’s treated with UV-C light before being sent back into the room, as well as air purifying mist. He believes it’s important to take an evidence-based approach to lowering the risks of post-op infections and believes future risk-reduction strategies need to involve surgeons, surgical professionals and infection preventionists. “They’ll lead the way,” he says, “but it’s surgical administrators who green light investments in effective solutions.” OSM