Ventilation-Based Strategy to Manage Intraoperative Aerosol Viral Transmission in the Era of SARS-CoV-2

Abstract

In operating theaters, ventilation systems are designed to protect the patient from airborne contamination for minimizing risks of surgical site infections (SSIs). Ventilation systems often produce an airflow pattern that continuously pushes air out of the area surrounding the operating table, and hence reduces the resident time of airborne pathogen-carrying particles at the patient's location. As a result, patient-released airborne particles due to the use of powered tools, such as surgical smoke and insufflated CO₂, typically circulate within the room. This circulation exposes the surgical team to airborne infection-especially when operating on a patient with infectious diseases, including COVID-19. This study examined the flow pattern of functional ventilation configurations in view of developing ventilation-based strategies to protect both the patient and the surgical team from aerosolized infections. A favorable design that minimized particle circulation was deduced using experimentally validated numerical models. The parameters adapted to quantify circulation of airborne particles were particles' half-life and elevation. The results show that the footprint of the outlet ducts and resulting flow pattern are important parameters for minimizing particle circulation. Overall, this study presents a modular framework for optimizing the ventilation systems that permits a switch in operation configuration to suit different operating procedures.

Keywords: COVID-19; SARS-CoV-2; aerosol viral transmission; operating room; safety; ventilation systems.

Figure 1

Experimental and numerical setups. (a) Image of the real operating room with the inlet duct highlighted (purple square). (b) Corner of the operating theater with one of the outlet ducts highlighted (red square). (c) Corresponding CFD domain geometry with the inlet (purple square) and outlet ducts (red squares) highlighted. (d) Representative schematic highlighting the positions (tripods) and directions (blue arrows) of the particle tracking cameras.

Figure 2

Model validation using measured and CFD-calculated particle streamlines in an empty OR. (a) The 3D schematic showing target view plane for the camera setup positioned at the outlet vent corner (View-plane 1). (b) The 3D schematic showing target view plane for the camera setup positioned at the corner without an outlet vent (View-plane 2). (c) Flow streamline on View-plane 1. (d) Flow streamline on View-plane 2. Dotted box in (c,d) highlights focus area of the camera in experiments. (e–h) Experimental airflow-tracing bubble tests performed in a fully equipped OR without the presence of the surgical staff. (e) Experimentally traced particle trajectory on View-plane 1. (f) Experimentally traced particle trajectory on View-plane 2. (g) Traced CFD-calculated particle trajectory on View-plane 1. (h) Traced CFD-calculated particle trajectory on View-plane 2.

Figure 3

Operation room ventilation system designs and particle dynamics. (a) Representative schematic of configuration C1. (b) The 3D steady state particle dynamics of configuration C1. (c) Representative schematic of configuration C2. (d) The 3D particle dynamics of configuration C2. (e) Representative schematic of configuration C3. (f) The 3D particle dynamics of configuration C3. Inlet ducts highlighted with purple squares and outlet ducts with red rectangles.

Figure 4

Flow streamline and particle spatial dynamics of adapted configurations. Steady state flow streamlines across the center ZX-plane of (a) Configuration C1, (b) Configuration C2, and (c) Configuration C3. Steady state spatial dynamics of particles in (d) Configuration C1, (e) Configuration C2, and (f) Configuration C3. Particle color map in (d–f) represents particle elevation.