Testing the efficacy of a portable anteroom system air fitter unit

AORN Journal,  June, 2008  by George Allen

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American Journal of Infection Control Hay 2008

Airborne infectious agents including Mycobacterium tuberculosis, the bacteria that causes tuberculosis (TB), are difficult to contain in most ORs that are designed to operate under positive air pressure in relation to the corridor. Positive air pressure prevents potentially contaminated air from the corridor from entering the OR when the door is opened, and thus protects the patient with an open incision who is at risk for the transmission of infection. In contrast, a patient with infectious TB is cared for in a negative pressure room which prevents air contaminated with the TB bacteria from rushing into the corridor when the door is opened and potentially exposing and infecting individuals outside of the room.

High-efficiency particulate air (HEPA) filter units capable of cleaning the air of TB bacteria also can mitigate the risk of occupational exposure to TB and improve air quality in the perioperative setting. The purpose of this study was to compare the effect of freestanding HEPA filter units commonly deployed in the OR to a novel portable anteroom system HEPA (PAS-HEPA) filter combination unit placed outside the OR and to assess the efficiency of particulate removal from an OR.

Sound-level monitoring was performed and smoke plume and submicron particles were observed during deployment of three different configurations of HEPA units. Two were different models of freestanding HEPA units deployed inside the OR immediately adjacent to the OR bed. The third was a PAS-HEPA unit placed outside the room. The PAS-HEPA combination unit consisted of

* a thermoplastic polymer anteroom envelope, adjustable in height from 7 ft to 10 ft 6 inches with a 12-inch diameter side exhaust port and a portable collapsible metal frame with an overall footprint of 34 inches x 61 inches;

* a negative pressure machine attached to the side exhaust port; and

* a flange (ie, door collar) secured to the OR door with sealing tape.

Data were collected in two separate phases on two different days. The first phase was limited to qualitative observation of smoke plume release, measurement of the concentration of submicron airborne particles, and measurement of noise pressure levels after deployment of the two free-standing HEPA units and the PAS-HEPA unit. During phase two, submicron particles were released in the OR, and measurement of the time taken for particle clearance was limited to the use of the PAS-HEPA unit. Common statistical techniques were used to analyze the data.

FINDINGS. Baseline noise levels with no freestanding HEPA units inside the OR were 45 decibels (dB) and 47 dB at one and five minutes. These levels increased to 69 dB and 68 dB, respectively, with one of the freestanding HEPA units and to 65 dB with the other unit. Noise levels with the PAS-HEPA unit outside the OR were essentially the same as the baseline: 48 dB and 49 dB at one minute and five minutes, respectively.

The smoke plume was not captured by the air filtration device of either of the freestanding HEPA units deployed inside the OR. Instead, the plume traveled vertically up from the OR bed into the breathing zone of personnel who normally would be around the table during the surgical procedure. By contrast, when the PAS-HEPA unit was used, the released plume was observed to be evacuated downward toward the main entry door and away from the sterile field. The PAS-HEPA unit, working in tandem with the OR heating, ventilation, and air conditioning system, removed more than 94% of an initial release of at least 500,000 submicron particles per cu ft within 20 minutes of release.

CLINICAL IMPLICATIONS. The results of this study revealed that when freestanding HEPA units were used, the plumes were drawn vertically upward and directly into the breathing zones where team members would be stationed during a surgical procedure. Additionally, the study confirmed that the PAS-HEPA unit evacuated the plume downward toward the main entry door and away from the sterile field. The researchers concluded that a PAS-HEPA unit is effective in removing submicron particles and will enhance the safety of patient care. Perioperative managers should understand that this study clearly indicates that the use of freestanding HEPA units in the OR during a surgical procedure should be avoided and that the PAS-HEPA unit may be an effective strategy to use when performing a surgical procedure on a patient with a disease such as tuberculosis that is spread via the airborne route.

GEORGE ALLEN, PHD, RN, CNOR, CIC

Olmsted RN. Pilot study of directional airflow and containment of airborne particles in the size of Mycobacterium tuberculosis in an operating room. Ant J Infect Control 2008;36(4):260-267.

GEORGE ALLEN

PHD, RN, CNOR, CIC

DIRECTOR OF INFECTION CONTROL

DOWNSTATE MEDICAL CENTER

BROOKLYN, NY

COPYRIGHT 2008 Association of Operating Room Nurses, Inc.
COPYRIGHT 2008 Gale, Cengage Learning