312. Mathematical Modeling of Pathogen Trajectory in a Patient Care Environment
Session: Poster Abstract Session: Assessing and Reducing Infection Risk
Friday, October 21, 2011
Room: Poster Hall B1
Background:  The Nebraska Biocontainment Unit (NBU) is a facility designed for the treatment of patients with highly infectious diseases.  The unit has single pass negative pressure airflow with a minimum of 15 air exchanges per hour. This study utilized mathematical modeling to evaluate particle trajectories and subsequent particle concentrations within regions of a patient care room.  The model provides clinically relevant data to minimize healthcare worker exposure to airborne infectious pathogens.

Methods:  Detailed quantitative mathematical modeling of airflow in a patient care room was achieved using the Ansys Fluent computational fluid dynamics software package.  Multiple models were created based on a release of particles from various locations in the room.  Computerized particle trajectories were presented in time-lapse fashion over a blueprint of the room.  A series of smoke tests were conducted to evaluate the model under each scenario.  Standard smoke test techniques were used along with the Superior Smoke #2B candle for airflow studies, which generates 8,000 cubic feet of smoke over a 60 second period.

Results: In a single occupancy room, most particles released from the head of the bed initially traveled towards the back wall, then lingered near the back portion of the room.  Particles rarely entered the bathroom, even when the door was open.  After a toilet flush, few particles escaped from the bathroom.  The models predicted that the areas of highest particle concentrations and thus highest potential exposure to a healthcare worker were the head of the bed, the foot of the bed, and the entry inside the bathroom after a toilet flush.

Conclusion: Mathematical modeling provides valuable information necessary to protect healthcare workers from exposure to airborne infectious diseases.  Based on the results of these models, healthcare workers in the NBU will be advised on which areas in the patient care room are at highest risk for exposures to airborne particles.  The model also facilitates optimal arrangement of the furniture and equipment in the room.  Mathematical modeling of particle flow in negative airflow settings may be applicable to multiple healthcare settings and could potentially serve as a modality to enhance the protection of healthcare workers.

Subject Category: N. Hospital-acquired and surgical infections, infection control, and health outcomes including general public health and health services research

Angela Hewlett, MD, MS1, Scott Whitney, PhD2, Shawn Gibbs, PhD3, Hendrik Viljoen, PhD1,2 and Philip Smith, MD, FIDSA1, (1)Division of Infectious Diseases, University of Nebraska Medical Center, Omaha, NE, (2)Department of Chemical and Biomolecular Engineering, University of Nebraska- Lincoln, Lincoln, NE, (3) Department of Environmental, Agricultural & Occupational Health, University of Nebraska Medical Center, Omaha, NE


A. Hewlett, None

S. Whitney, None

S. Gibbs, None

H. Viljoen, None

P. Smith, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.