A new study from a leader in airborne disease research indicates that Operating Room HEPA filtration is not a guarantee against nosocomial infection. Dr. Russel Olmstead led a team that looked at airborne contamination inside of the OR environment.

Pilot study reinforces use of portable anteroom HEPA filtration

To prevent perioperative transmission of airborne microorganisms

Washington, DC, May 6, 2008 – Amidst an increase in new tuberculosis cases, researchers have begun investigating the effectiveness of new operating room filtration systems designed to protect staff and patients. According to pilot study findings published in the May issue of the American Journal of Infection Control, a supplemental portable anteroom high-efficiency particulate air (PAS- HEPA) filter unit placed outside operating room suites may prevent secondary transmission of airborne microorganisms like Mycobacterium tuberculosis (M. tuberculosis).

“The rate of decline in newly reported tuberculosis cases in the U.S. has slowed,” said lead study investigator Russell N. Olmsted, MPH, CIC, epidemiologist from Saint Joseph Mercy Hospital in Ann Arbor, MI. “This, coupled with the worldwide emergence of even more drug-resistant tuberculosis, reinforces the need for renewed vigilance and surveillance from healthcare professionals. In particular, study results reinforce the need for measures to optimize air particle removal.”

Olmsted and colleagues compared the efficiency of freestanding HEPA filtration units to a new portable anteroom system (PAS)-HEPA combination unit in removing harmful airborne infectious pathogens. Freestanding HEPA units were evaluated in the operating room, while the PAS-HEPA unit was placed outside over the main operating room door. Both smoke plume and non-infectious particles similar in size to M. tuberculosis were used to mimic movement of airborne pathogens within highly pressured environments.

“We observed interruption of normal patterns of airflow with freestanding HEPA units placed inside the operating room,” said Olmsted, adding that instead of being captured by the air-filtration system, smoke plume traveled upward from the operating room table and into the breathing zone of personnel who might be present during a typical surgical procedure.

“This suggests an increased potential for occupational exposure to airborne microorganisms as well as an unwanted introduction of contaminants into the patient’s open surgical site,” he explained.

In contrast, deployment of the PAS-HEPA combination unit pulled the smoke downward, away from the operating room table and toward the floor and main door. The second phase of the study (which involved simulated microscopic particles) mirrored these observations; within 20 minutes, over 94% of submicron particles were cleared from the operating room.

“The results of Mr. Olmsted’s study reinforce the Centers for Disease Control and Prevention (CDC) 2003 guidelines for environmental infection control as well as 2005 guidelines for preventing the transmission of M. tuberculosis in healthcare settings,” said Janet E. Frain, RN, CIC, CPHQ, CPHRM, APIC 2008 President and Director, Integrated Services, Sutter Medical Center in Sacramento, CA. “These findings should be considered for integration into an overall infection prevention and control program to help ensure both patient and healthcare personnel safety.”

These findings substantiate results we've discovered in our testing of Operating Rooms. Recently we found microbial contamination (including fungi) immediately downstream from HEPA filtration units installed in ORs. The contamination was found one week after the filters were certified for efficiency compliance.
Filters are great for trapping microorganisms, but they do not 'kill'. Eventually filters can become colonized and act as a breeding ground for pathogens. Thinking that you have 100% protection because you have HEPA filtration is a false sense of security.
We suggest a balance between UV and filtration to provide a better strategy for reducing environmental pathogens in critical care areas of your hospital. E-mail us to find out more about a recent study in which VIGILAIR provided better protection than laminar flow for operating suites in a large urban hospital.