Assessment of Health-Care Worker Exposure to Pandemic Flu in Hospital Rooms

This study examines the effectiveness of a current Airborne Infection Isolation Room (AIIR) in protecting health-care workers (HCWs) from airborne-infection (AI) exposure, and compares HCW AI exposures within an AIIR and a traditional patient room. We numerically simulated the air-flow patterns in the rooms, using room geometries and layout (room dimensions, bathroom dimensions and details, placement of vents and furniture), ventilation parameters (flow rates at the inlet and outlet vents, diffuser design, thermal sources, etc.), and pressurization corresponding to those measured at a local hospital. A patient-cough was introduced into each simulation, and the AI dispersal was tracked in time using a multi-phase flow simulation approach. The measured data showed that ventilation rates for both rooms exceeded 12 air-changes per hour (ACH), and the AIIR was at almost 16 ACH. Thus, the AIIR met the recommended design criteria for ventilation rate and pressurization. However, the computed results revealed incomplete air mixing, and not all of the room air was changed 12 (or 16) times per hour. In fact, in some regions of the room, the air merely circulated, and did not refresh. With the main exhaust flow rate exceeding the main supply, mass flow rate conservation required a part of the deficit to be accounted for by air migration from the corridor through the gaps around the main door. Hence, the AIIR was effective in containing the "infectious aerosol" within the room. However, it showed increased exposure of the HCW to the AI pathogens, as the flow from the ceiling-mounted supply louver first encountered the patient and then the HCW almost directly on its way to the main exhaust, also located on the ceiling. The traditional patient room exhibited a similar flow path. In addition, for the traditional patient room, some cough-generated aerosol is observed very close to the gaps around the door to the corridor, indicating that the aerosol may escape to the corridor, and spread the infection beyond the room. The computational results suggest that ventilation arrangement can have an important role in better protecting the HCW from exposure to airborne infectious pathogens.