(195d) Testing the Effectiveness of Free-Standing Hepa Filters Placed in Operating Rooms to Reduce the Spread of Contaminated Particles Using Computational Fluid Dynamics

Heating, Ventilation and Air-conditioning (HVAC) systems within an operating room (OR) are dynamic systems that affect the airflow. Airflow patterns are a major contributor in moving contaminated particles in an enclosed space. When the airflow pattern in the OR is disrupted, bacteria may come into contact with an open surgical wound and cause a surgical site infection (SSI). SSIs account for as much as $10 billion annually in direct and indirect medical costs.¹ Reducing the rate of post-surgical infection is of great importance in the medical industry. To address these issues, The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has developed airflow and ventilation standards for health care facilities. Filtered air contains lower amounts of airborne bacteria compared to unfiltered air, helping to reduce the chance of SSI. A study by van der Heide et al. showed that a high-efficiency particulate air (HEPA) filter, filtered 70% of 0.3 µm particles and 95% 1.0 µm particles.^2,3 HEPA filters have been implemented in the OR, particularly at the inlet vent above the operating room table to ensure clean air is entering the OR. However, this does not prevent the spread of contaminated particles that are derived and transmitted within the OR. Gram-positive cocci are the most common bacteria associated with SSIs and are typically transmitted via the shedding of the patient’s or health-care team’s skin.⁴

The global COVID-19 pandemic has caused additional concern about the transmission of the severe acute respiratory syndrome coronavirus (SARS-CoV-2) within the OR. Preventing the spread of COVID-19, caused by SARS-CoV-2, is extremely important in today’s global circumstances. The inclusion of free-standing HEPA filters within the OR accounts for these issues by taking in the potentially contaminated air and exhausting out clean air. Furthermore, HEPA filters increase the number of air changes per hour (ACH).⁵ HEPA filters have a standardized efficiency of 99.7% rating for removing particles equal to 0.3 micrometers. The size of skin cells that carry bacteria are typically between 8 to 15 micrometers.⁴ The SARS-CoV-2 particles are postulated by the Center for Disease Control to be spread via respiratory droplets and typically larger than 5 micrometers.⁶ Therefore, the addition of HEPA filtration units to the OR should reduce the airborne particulate matter and further protect patients from SSIs and SARS-CoV-2.

This study investigates how a free-standing HEPA filter affects the overall airflow inside the OR and tracks how contaminated particles move within the space. A model of the OR with the filtration unit was created in Dassault Systemes Solidworks (Waltham, MA) and then transferred to ANSYS Fluent (Canonsburg, PA). The free-standing HEPA filter was placed at different locations to assess the overall airflow patterns in the OR. The ACH within the OR was tracked to determine the optimal location for the free-standing filter without interfering with the airflow needed to reduce SSIs.

References

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