Risk Assessment of Infectious-Bioaerosol exposures to hospital Health-Care Workers. Development and Testing of innovative Medical Countermeasures in Isolation Room

An efficient ventilation configuration of an airborne infection isolation room (AIIR) is essential for protecting Health care workers (HCW) from exposure to potentially-infectious patient aerosol. This document presents a Computational Fluid Dynamics (CFD) study to predict airflow distribution and the bioaerosol dispersal originiating from an infectious patient for a range of AIIR ventilation configuration design considerations.;The Computational Fluid Dynamic analysis of the air flow patterns and bioaerosol dispersal behavior in Mock AIIR is conducted using the room geometries and layout (AIIR dimensions, bathroom dimensions, placement of vents and furniture), ventilation parameters and pressurization corresponding to that of a traditional ceiling mounted ventilation arrangement observed in existing hospitals. The measured data shows that ventilation rates for the NIOSH AIIR is about 12 ACH. Two life-sized breathing human models are used to simulate a source patient and a receiving HCW. A single patient-cough cycle is introduced into the simulation, and the airborne infection dispersal is tracked in time using a multi-phase flow simulation approach.;In the present study with ventilation configuration 1, the AIIR has two supply vents and 1 exhaust grille corresponding to that of a traditional ceiling mounted ventilation arrangement observed in existing hospitals.;In the Original and Alternate AIIR ventilation, the results reveal air recirculation regions that diminishes the effect of air filtration and prolongs the presence of flu contaminated air at HCW's zone. Within 0.7s after patient coughs, the HCW is at risk of acquiring the infectious influenza disease, as a portion of these aerosols are inhaled by the HCW.;As the time progresses, the aerosols eventually spread throughout the entire room. Subsequently, a portion of these aerosols are removed by the exhaust. However, the remaining cough aerosols re-enter and re-circulate in the HCW's zone, until they are removed by the exhaust. The Overall duration of influenza infection in the room is recorded as more than 20s. With successive coughing events, a near-continuous exposure would be possible.;Alternate ventilation configuration 2 retains the linear supply diffuser in ventilation configuration 1 but interchanges the Square supply and Main Exhaust locations. The results show the ceiling-ventilation arrangement of Mock Original and Alternate AIIRs creates an unfavorable environment to the HCW throughout his stay in AIIR.;A Novel Medical Countermeasure, namely, Direct-Control Exhaust Ventilation Configuration Intervention technique evaluated in this study has the ceiling exhaust replaced with vented headboard mantle and canopy arrangement, while supply diffusers locations remain the same as configuration 2.;Furthermore, the effects of shifting HCW's location on room air distribution and bioaerosol dispersal behavior is studied to ensure whether Direct-Control exhaust configuration is efficient in protecting HCW from patient's cough aerosols.;For the Direct-Control Exhaust Ventilation developed in this study, the results show that it is the most efficient in preventing the patient's bioaerosols from entering HCW's region. Further evaluation of this configuration is recommended for potential adoption within new and existing AIIRs to reduce the potential impact of infectious epidemics on severe workforce absenteeism and our nation's significant financial losses.