![]() Specifications such as the floor area, airflow quantity and pressure gradient were designed to meet the requirements of the British operating theatre standards, which have been commonly used as reference in Hong Kong. Similar to all other operating theatres in Hong Kong around that period and up to the present day, the operating theatres were maintained at a positive pressure. The original operating theatre suite in this hospital was built in 1994. The construction of this permanent negative pressure operating theatre was completed in June 2004. 2 Afterwards, the hospital management decided that a permanent negative pressure operating theatre was necessary, in anticipation of SARS returning and for those patients contracting similar infectious airborne diseases such as tuberculosis and severe influenza. This temporary negative pressure theatre worked well during the SARS crisis. The pressure differential was maintained by sealing the entrance doors with disposable sticky tape after the patient was transported into the room. This was achieved by incorporating two strong exhaust fans next to the original exhaust system. Over a short period, one of the 11 operating theatres in the main operating suite of the hospital was converted temporarily into a negative pressure theatre. Most SARS patients admitted to the United Christian Hospital during the crisis were residents of Amoy Gardens, where the largest transmission of community-acquired SARS occurred. 1 However, a negative pressure operating theatre offers optimal protection to personnel working in adjacent areas. In principle, a positive pressure operating theatre with adequate air changes could quickly eliminate the virus from the environment, and it has been shown that the risk of cross-contamination from airborne infection is low if staff are adequately protected with appropriate personal protective equipment (PPE). When these patients required operative procedures, a negative pressure theatre was considered to be more suitable than a positive pressure environment. ![]() Generally, SARS patients were accommodated in negative pressure isolation rooms on the ward. The severe acute respiratory syndrome (SARS) crisis in Hong Kong from March to June 2003 resulted in extreme stresses and strains on the general running of hospitals. The simulation results show that the physical environment and the dispersion pattern of bacteria in the negative pressure theatre were as good as, if not better than, those in the original positive pressure design. Computational fluid dynamics, a computer modelling technique, was used to compare the distribution of room air before and after the design changes from positive to negative pressure. This has also been confirmed by regular air sampling checks. Since entering regular service, routine measurements and observations have indicated that the airflow performance has been satisfactory. This article describes the physical conversion of a standard positive pressure operating theatre into a negative pressure environment, problems encountered, airflow design, and evaluation of performance. It is currently used for treatment of suspected or confirmed airborne infection cases, and was built in anticipation of a return of SARS, an outbreak of avian influenza or other respiratory epidemics. The severe acute respiratory syndrome (SARS) crisis led to the construction of a negative pressure operating theatre at a hospital in Hong Kong.
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