Medical staff's movement effects on particle counts in a surgical zone

Abstract

Movement by humans in healthcare facilities is unpreventable, especially among medical staff performing surgical procedures in an operating room. The movements can generate a secondary airflow that interrupts air supplies from ceiling-mounted diffuser, that serves to remove airborne particles from surgical zone. Consequently, the movement of particles in the surgical zone is affected, and the tendency of particles to fall onto patient’s wound is increased. This situation could elevate the chances of a patient contracting surgical site infections and could increase the risk of death. The present study aims to examine the effects of medical staff’s turning movements on the number of particles falling onto a patient. A simplified computational fluid dynamics (CFD) model of the operating room was developed and validated based on published data. A Re-Normalisation Group k-e turbulence model based on the Reynolds-Averaged Navier-Stokes equations was used to simulate airflow, while a discrete phase model was used to simulate movement of airborne particles. The medical staff’s turning movements were controlled by integrating a user-defined function code and using a dynamic mesh method. Results show that medical staff’s turning movements have a significant influence on the airflow velocity distribution and the airborne particle concentration around the patient. Replacing the turning bent-forearm medical staff with the stationary bent-forearm medical staff reduced the number of particles that settled on a patient by 60.9 %, while substituting the turning straight-forearm medical staff with the stationary straight-forearm medical staff lowered the settlement of particles by 37.5 %. Results also indicated that employing single large diffuser (SLD) ventilation in the operating room, it reduced the number of particles that move into the surgical zone under the influence of medical staff’s turning movements. The particles that settled on the patient were reduced by 41 % and 39 % when using the SLD 1 and SLD 2 ventilation, respectively. Present work confirmed that integrating the medical staff’s turning movement in the vicinity of surgical zone is important as it reflects a more realistic condition. Considering only the stationary medical staff in simulation could underestimate the number of particles move into the surgical site and settling on a patient.