Search PubMed⌕ Search

Biomedical subjects

T T Chow

Publications and source records attributed to T T Chow.

9 recordsLinked to original sources
PubMed2006

Conversion of operating theatre from positive to negative pressure environment.

The severe acute respiratory syndrome (SARS) crisis led to the construction of a negative pressure operating theatre at a hospital in Hong Kong. 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. 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. Since entering regular service, routine measurements and observations have indicated that the airflow performance has been satisfactory. This has also been confirmed by regular air sampling checks. 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. 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.

Aerosols↗
PubMed2005

Ventilation performance in the operating theatre against airborne infection: numerical study on an ultra-clean system.

A laminar airflow study was performed in a standard operating theatre in Hong Kong, the design of which followed the requirements of the UK Health Technical Memorandum. The study of the ultra-clean ventilation system investigated the effectiveness of the laminar flow in: (i) preventing bioaerosols released by the surgical staff from causing postoperative infection of the patient; and (ii) protecting the surgical team against infection by bacteria from the wound site. Seven cases of computer simulation are presented and the sensitivity of individual cases is discussed. Air velocity at the supply diffuser has been identified as one of the most important factors in governing the dispersion of airborne infectious particles. Higher velocity within the laminar regime is advantageous in minimizing the heat-dissipation effect, and to ensure an adequate washing effect against particulate settlement. Inappropriate positioning of the medical lamps can be detrimental. Omission of a partial wall may increase the infection risk of the surgical team due to the ingression of room air at the supply diffuser periphery. This paper stresses that a successful outcome in preventing airborne infection depends as much on resolving human factors as on overcoming technical obstacles.

Air Microbiology↗
PubMed2004

Ventilation performance in operating theatres against airborne infection: review of research activities and practical guidance.

Surgical site infection risk due to airborne bacteria is a key area of consideration in developing operating theatre ventilation design and monitoring procedures. This paper reviews the recent extensive research into operating theatre ventilation development in relation to the design concepts in operating theatre layout, pressurization and ventilation, particularly the evolvement of ultra-clean ventilation. The findings that led to the current technical standards and the developments of microbial measurements and numerical techniques are discussed. Since the late 1980s, computational fluid dynamics has been a fast developing tool used in the prediction of room air distribution and contaminant dispersion. The basic principles and current practice applying to operating theatre ventilation studies are introduced.

Air Microbiology↗
PubMed2004

Effects of freezing and drying grass products prior to fatty acid extraction on grass fatty acid and lipid class composition--a technical note.

Grass and grass silage represent a rich and natural source of omega-3 polyunsaturated fatty acids, in particular linolenic acid, for ruminants. Recent research, focusing on improving the content of these beneficial fatty acids in grass, requires storage of the forage samples prior to analysis. In this study, we evaluated whether conservation of fresh grass and grass silage by freezing (1 and 4 weeks,--18 degrees C) and/or drying (24h, 50 degrees C) affected its fatty acid content and induced shifts between lipid classes. FA were extracted using chloroform/methanol (2/1, v/v) and triacylglycerols (TAG), free fatty acids (FFA) and polar lipids (PL) were separated by thin layer chromatography. Fatty methyl esters (FAME) were identified by gas chromatography. Loss of thawing liquor might provoke a dramatic decrease in extractable lipid after frozen storage of both grass and grass silage. Morever, after frozen storage, fatty acids in grass but not in grass silage seem subjected to a higher rate o f lipolysis and oxidation, as suggested by increased quantities of FFA (3.1, 7.6, 8.4 % of total FAME) and reduced proportions of poly-unsaturated fatty acids (79.5, 73.6 and 74.1 % of total FAME) when analysing fresh grass samples directly or after 1 and 4 weeks of frozen storage, respectively. Drying of fresh grass did not provoke changes in FA composition, but distribution of FA over lipid classes was significantly altered, with an increase in TAG (5.1 to 17.9 % of total FAME) and FFA (2.4 to 14.9 % of total FAME) and lower proportions of PL (90.7 to 55.7 % of total FAME).

Animal Feed↗
PubMed1976

Diagnostic ultrasound in the management of patients using intrauterine contraceptive devices.

A group of 80 patients was scanned by ultrasound within 24 hours of insertion of an intrauterine contraceptive device (IUCD) and re-examined clinically and/or by ultrasound after the next menstrual period. An attempt was made to identify factors such as uterine size, uterine flexion and the position of the IUCD which might be related to its expulsion or removal when, on initial scanning, the device was not located in the fundal area; removal was necessary in 5 out of 6 patients. In patients with an endometrial cavity of less than 40 mm length and/or acute uterine flexion, the overall figure for expulsion and removal was 54 per cent (13 out of 24). It is hoped that a consideration of these factors will lead to a reduction of the failure rate of the IUCD.

Cervix Uteri↗