Evaluation of airborne contaminant exposure in a single-bed isolation ward equipped with a protected occupied zone ventilation system

Abstract

Effective ventilation in general hospital wards is important for controlling the transmission of airborne infectious agents that may cause respiratory diseases. This study investigates the potential of protected occupied zone ventilation (POV) to reduce the risk of cross-infection in hospital isolation wards. Two life-size breathing thermal manikins were used to simulate an infected patient lying in a bed and a sitting, receiving health care worker. N 2 O was used as a tracer gas to simulate the droplet nuclei exhaled by patients. The contaminant exposure index <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>ε</mml:mi> <mml:mrow> <mml:mi>e</mml:mi> <mml:mi>x</mml:mi> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> was used to assess the risk of cross-infection for different configurations of the supply velocity, the patient’s lying position and the exhaust openings. The contaminant exposure index <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mtext> </mml:mtext> <mml:mrow> <mml:mo stretchy="true">(</mml:mo> <mml:mrow> <mml:msub> <mml:mi>ε</mml:mi> <mml:mrow> <mml:mi>e</mml:mi> <mml:mi>x</mml:mi> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mo stretchy="true">)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> shows that the ventilation strategy is effective, but this is also highly dependent on the supply velocity and the location of the exhaust relative to the patient’s breathing zone. The patient’s posterior position does not affect the personal exposure of the receiving patient. Compared to traditional ventilation systems, the POV system can reduce the risk of cross-infection in hospital isolation rooms. The full potential of a POV system can be achieved in an isolation ward where movement between the infected and protected zones is restricted or prohibited.