This study examines the efficacy of currently used Airborne Infection Isolation Rooms (AIIRs), also called Negative Pressure Rooms, in protecting Health-Care Workers (HCWs) from contact with airborne virus while conducting cough-generating procedures on patients diagnosed with Pandemic-flu (PANFLU). During these procedures, the patient coughs out contagious droplets, which are capable of causing infection if inhaled by the health-care worker. The work is motivated by the need to assess how ventilation design affects the air flow in the room with the goal of mitigating contact of the HCWs to this infection.
Numerical simulation has been carried out to determine the air flow pattern in an AIIR corresponding to the geometrical lay-out and the current ventilation parameters in a local hospital. The patient and the HCW were modeled using available anthropometric data. The HCW is in a standing position at a distance of one inch from the patient’s bed, as the HCW carries out the cough-generating procedure on the patient, to simulate a real life situation. Afterwards, a patient cough was introduced from the patient’s mouth, and the dispersed virus-carrying droplets were tracked in time.
The ventilation set-up in the AIIR was effective in containing the infection within the room. With the main exhaust flow rate slightly exceeding the main inlet flow rate, mass flow rate conservation required air from the corridor to enter the room through the gaps around the main door to the room. In the first two seconds after being ejected from the patient’s mouth, the cough droplets rise in the air and form a “cloud” above the patient. A part of the flow from the main inlet on the ceiling passes just below the cough, and encounters the patient and then the HCW almost directly in its path. It then recirculates behind the HCW and is pulled by the main exhaust, also located on the ceiling. Due to their size (≈5 micron), the droplets follow the local path of the air, and some of the droplets travel towards the lower part of the HCW’s body, and are eventually pulled in the direction of the exhaust. The rest of the air coming from the inlet is pulled directly by the exhaust, without encountering the patient and HCW in its path. Some of the droplets follow these pathlines, and travel towards lower half of the patient’s bed in the direction of the exhaust. Most of the other droplets remain airborne, and gradually follow the air flow towards the exhaust. The diameter of some droplets is found to be more than 5 microns and these droplets may tend to move around inside the room, independent of the prevailing flow pathlines.
The computational results show that AIIR is effective in containing the cough droplets inside the room. However, since some of the droplets travel in the vicinity of the HCW, the AIIR was not adequately effective in protecting the HCW from contact with the cough droplets. Hence, to alter the air flow patterns in the AIIR, consideration of alternate ventilation arrangements is warranted to better protect the HCW from contact with the airborne infectious cough droplets emitted by the patient.