Design of convertible patient care unit for both non-pandemic and pandemic times: Prototype, building spatial layout, and ventilation design

Convertible patient care units can accommodate non-respiratory infectious disease patients in non-pandemic times and provide isolated treatment for respiratory infectious disease patients during pandemic times. A prototype convertible patient care unit covering a floor area of 1518 m², featuring 16 wards, and accommodating 40 beds was developed to examine the impact of building spatial layout and ventilation design on the inter-zonal airborne transmission and energy use intensity (EUI) during both non-pandemic and pandemic times. Building spatial layout referred to the presence of patient corridors and anterooms, while ventilation design referred to the location of air terminals and the calculation method of residual air volume (namely, difference between supply and exhaust airflow rates). Adding anterooms provided an 18% reduction in pressure gradient fluctuations during door-opening events. The absence of exhaust in the medical corridor, anterooms, and wards increased contamination leakages to the patient corridors. Using the differential pressure method to calculate residual air volume was more effective in controlling the inter-zonal pressure gradient than the fixed residual air volume method. Various conversion methods resulted in an 84%-134% increase of EUI compared to non-pandemic times, without, however, corresponding reduction in inter-zonal airborne transmission risk. The condition of adding both patient corridors and anterooms, exhaust-only patient corridors, anterooms with balanced supply-exhaust airflow rates, and differential pressure method to calculate residual air volume were effective conversion strategies to simultaneously address both the inter-zonal airborne transmission and EUI. These findings provide fundamental information for designing convertible patient care units and revising related guidelines in China.