| The design of airborne infection isolation (AII) room has become one of the major research domains following the emergence of the global concern of acute respiratory diseases in this century. These include severe acute respiratory syndrome (SARS) in 2003, H5N1 avian influenza, and pandemic influenza H1N1 in 2009. All of which have claimed thousands of lives. Even with the current stringent design and practice guidelines, nosocomial infection of healthcare workers (HCWs) and inpatients continues to occur. This implies that there might be limitations in current isolation ward designs.;Many patients with severe respiratory infection require supportive therapy for respiratory failure. Common interventions involve supplemental oxygen to improve tissue oxygenation. In the worst scenario, mechanical ventilation via non-invasive positive pressure ventilation (NPPV) may be required. Since a large amount of aerosols is generated during these interventions, there is a great risk of spreading infectious aerosols from the respiratory tract of the patient to the surrounding environment.;According to recommendations from the Facility Guidelines Institute (FGI) of the American Institute of Architects (AIA), World Health Organization (WHO) and Center for Disease Control and Prevention (CDC), a common engineering approach to isolation room design is to maintain the air ventilation rate at a minimum of 12 air changes per hour (ACH) for mixing and dilution, and a negative pressure in the room to direct airflow inwards, instead of leaking outwards.;In collaborations with physicians in the Respiratory Division and the Intensive Care Unit (ICU) at the Chinese University of Hong Kong (CUHK), a series of experiments were carried out to verify the ventilation performance of an All room at the Princess Margaret Hospital (PMH). Experiments investigated the effects of ACH, the control of airflow direction, the air tightness of the automatic swing door and the application of positive pressure ventilation procedures, such as high flow rate oxygen masks, jet nebulizers and NPPV. These were extensively tested in two different isolation rooms of the Prince of Wales Hospital (PWH) and PMH, under common clinical circumstances and environmental conditions.;The experiments implemented a high-fidelity human patient simulator (HPS) which could be programmed with different lung breathing conditions and oxygen flow rate settings. The patient exhaled air dispersion distances and airflow patterns were captured in detail with a non-intrusive, laser light sheet, smoke particle scattering technique, designed for this thesis. Thin laser light sheets were generated by a high energy YAG laser with custom cylindrical optics. Smoke concentration in the patient exhaled air and leakage jets was estimated from the intensity of light scattered, which was then expressed as nonnalized particle concentration contours using computer programs developed for this study.;The study quantitatively revealed the distinctive patient exhaled airflow patterns and the extent of bioaerosol, generated directly from the patient source with the application of different oxygen delivery interventions for different patient lung conditions and oxygen flow rates. It was found that contamination was more critical during the administration of oxygen therapies, which is common in clinical circumstances. Source control is therefore the most efficient and effective approach to the reduction and even elimination of patient exhaled bioaerosol contaminants. Thus, when working in an isolation room environment, full preventive measure should be taken and it is essential to consider the location of mechanical vents and the patient exhaled airflow patterns. It has also been shown in experiment that applications of bacterial viral filter could be a solution to the problem.;The aerodynamic data in this thesis infonns architects and engineers on how to improve the hospital ward ventilation design so as to avoid aerosol and ventilation leakage. Ultimately, it is hoped that this work may play a role in preventing devastating nosocomial outbreaks in the future. |
