Pilot study of directional airflow and containment of airborne particles in the size of Mycobacterium tuberculosis in an operating room
Background
Containment of airborne microorganisms to prevent transmission in a positively pressured operating room (OR) is challenging. Occupational transmission of Mycobacterium tuberculosis (M tuberculosis) to perioperative personnel has occurred, but protection of the surgical site is of equal importance. High-efficiency particulate air (HEPA) filters can mitigate occupational exposure and improve air quality. Smoke plumes and submicron particulates were released to simulate aerobiology of M tuberculosis and assess impact and efficacy of particle removal in an OR suite using different HEPA filtration units and configurations.
Objectives
My objectives were to compare the impact of freestanding HEPA filter units, which are currently more commonly deployed inside the OR, with a novel portable anteroom system (PAS)-HEPA combination unit (PAS-HEPA) placed outside the OR and assess the efficiency of removal of particulates from an OR.
Methods
Smoke plume and submicron particles were generated inside an OR. Plume behavior was observed during deployment of 3 different configurations of HEPA units. Two of these involved different models of freestanding HEPA filtration units inside the OR, and the third was the PAS-HEPA unit located outside the OR. The concentration of submicron airborne particles was quantified for each configuration of freestanding HEPA and PAS-HEPA units. In addition to measurement of submicron airborne particulates, a high concentration of these was generated in the OR, and time for removal was quantified.
Results
Observations of released plumes, using the PAS-HEPA unit revealed a downward evacuation, away and toward the main entry door from the sterile field. By contrast, when portable freestanding HEPA units were placed inside the OR, plumes moved vertically upward and directly into the breathing zone of where the surgical team would be stationed during a procedure. The PAS-HEPA unit, working in tandem with the OR heating, ventilation, and air conditioning system, was confirmed to have removed over 94% of an initial release of at least 500,000 submicron particles/ft3 within 20 minutes after release.
Conclusion
This pilot study clearly indicates that avoiding the use of freestanding HEPA filters inside an OR during a surgical procedure is prudent and consistent with Centers for Disease Control and Prevention guidelines. A PAS-HEPA unit is effective in removing submicron particles and will enhance safety of care of a patient with an airborne infection requiring surgery.
Infection Control Services, Saint Joseph Mercy Health System, Ann Arbor, MI
Address correspondence to Russell N. Olmsted, MPH, CIC, Infection Control Services, Saint Joseph Mercy Hospital, 5301 E. Huron River Dr, Ann Arbor, MI 48106-0995.
Supported by Mintie Technologies, Inc., which included provision of some of the materials plus underwriting cost for environmental testing and air balancing services. Under the aegis of APIC Strategic Partnership Program, Mr. Olmsted has also provided educational training that was sponsored by Mintie Technologies, Inc.
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