Pilot Study Reinforces Use of Portable Anteroom HEPA Filtration to Prevent Perioperative Transmission of Airborne Microorganisms

WASHINGTON, D.C. — 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, Mich. “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, more than  94 percent 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’s 2008 president and director of integrated services at Sutter Medical Center in Sacramento, Calif. “These findings should be considered for integration into an overall infection prevention and control program to help ensure both patient and healthcare personnel safety.”

Olmsted emphasized that infection prevention professionals should review both of these guidelines along with the compendium of corrections that accompanies the 2005 tuberculosis recommendations, paying particular attention to information regarding the use of portable air filtration units during surgical procedures.

The investigators concluded that supplemental PAS-HEPA filtration appears to be an effective strategy for containing potential airborne infections. “It also offers clinicians the option of deployment at any point in a daily schedule of surgeries and can be moved with the patient to a private recovery room to avoid postoperative transmission,” Olmsted said. Nevertheless, he suggested that in order to validate these findings, additional data derived from other facilities are needed. He also cautioned that the use of surrogates to mimic M. tuberculosis made it impossible to truly predict pathogen transmission behavior.

Reference: AJIC. 2008; 36 [4]: 260-267.

Source: Association for Professionals in Infection Control and Epidemiology