Environmental circulation of airborne SARS-CoV-2 particles in intensive care rooms

Abstract Background: Airborne transmission is a major concern in intensive care units (ICUs). This study aimed to identify the determinants of airborne and surface contamination in ICU rooms occupied by patients with COVID-19 associated respiratory failure. Methods: Observational study in a tertiary care hospital comprising six ICUs with diverse architectural layouts and HVAC systems. We modeled the dispersion of respiratory particles in five rooms using computational fluid dynamics (CFD). Air and surface samples were collected at predefined locations in 19 rooms occupied by 28 patients testing positive for SARS-CoV-2. Risk factors associated with environmental contamination were identified using classification tree analysis. Results: Measured HVAC airflow rates were substantially lower than programmed values in three ICUs. CFD simulations suggested that exhaled particles initially rose above the patient, accumulated beneath the ceiling, and subsequently dispersed in the room. SARS-CoV-2 was detected in 14/64 (22%) air samples and 60/134 (45%) surface samples. The most important determinants of environmental contamination were patient viral load, room characteristics, and mode of respiratory support. Environmental contamination was more frequent in rooms with low airflow rates and extraction vents located outside the room. Conclusion: In our ICUs, the main factors associated with environmental detection of SARS-CoV-2 particles were patient airway viral load, the flow rate and location of the exhaust ventilation system, and the use of mechanical ventilation. These results could help guide the renovation or construction of intensive care rooms.