Particle Aerosolization during Tracheostomy Procedure as Modeled by Computational Fluid Dynamics

ABSTRACT

Introduction SARS-CoV-2 has created a hazardous environment for healthcare workers, with some of the riskiest procedures being those that generate aerosolized particles, such as tracheostomy surgery. Tracheostomy is both particle aerosolizing and extremely common, particularly for patients in respiratory distress. We utilized computational fluid dynamics (CFD) to model aerosolized particle spread during tracheostomy to deduce the viral loading risks posed to surgeons and anesthesiologists by aerosolized viruses. Additionally, we studied how these risks change with varying tracheal incision sizes. MethodsAn intubated subject's CT scan was virtually modified to replicate the tracheostomy procedure. An anatomically accurate trachea, thorax, incision, and operating room were created. Airflow simulations were performed to reproduce the exhalation occurring with removal of the intubation tube and opening of the airway to room pressure. Particles were released into the trachea from the primary bronchi, which then escaped into open air via the tracheal incision. Three tracheal incision sizes were modeled. Four particle sizes were released (0.2μ m-20μ m). Airflow was modeled for 20 seconds. ResultsFor small, medium, and large incisions, 68.7%, 68.4%, and 68.5% of particles by mass remained in the trachea, respectively (68.5% average of the three) (Figure1). Average size of escaped particles was 5.31μ m, 5.27μ m, and 5.29μ m for the small, medium, and large incisions respectively, while average particle size remaining in the trachea was 14.0μ m, 14.66μ m, 14.29μ m.From 4 to 8 seconds after initial particle release, the average particle size falling to the level of the patient's forehead increased from 11.6μ m to 18.4μ m. Large particles (10μ -20μ m) fell quickly, while smaller particles (0.2μ m to 2μ m) were more likely to remain suspended in air after 20 seconds. ConclusionsCFD particle aerosolization modeling of tracheostomy procedures can predict the viral loads healthcare workers are exposed to for the purpose of implementing proper safety precautions. These results highlight the extended residence times of aerosols in the absence of room ventilation which should ordinarily clear suspended particles, as well as the importance of considering smaller particles when designing personal protective equipment (PPE) for hospital staff. Large particles fall due to gravity relatively quickly, meaning the largest viral loads are airborne immediately after exhalation. Tracheal incision size was insignificant to the amount of aerosol generated during tracheostomy. In the absence of proper room ventilation, particles remained suspended in highest concentration directly above the patient's forehead, not directly above the tracheal incision. This implies physicians in this relative danger zone, such as anesthesiologists, need additional safety precautions.