Lighting
Special requirements in UCV theatres
Graeme Hall FIHEEM, MIET, managing director of Brandon Medical, considers in detail the particular requirements and criteria for operating lights used in ultraclean ventilation (UCV) theatres, and explains how the recent establishment of a standard for testing of lighting’s suitability for such theatre environments will help designers and manufacturers, as well as those specifying UCV theatre illumination, going forward.
replacement surgery. The first artificial hips were developed by Prof. John Charnley, a famous British orthopaedic surgeon, who, having spent a period professionally at Manchester Royal Infirmary in the late 1940s (having been appointed a joint honorary assistant orthopaedic surgeon there in 1947) subsequently established a pioneering hip surgery centre at Wrightington Hospital in Lancashire. During this ‘pioneering’ period, having encountered a high incidence of infections during such surgery, Prof. Charnley traced the source of infections to airborne particles falling into the wound, most of which were skin cells from the surgeons and clinical staff in the theatres. Prof. Charnley enlisted the help of a local specialist in clean air systems to develop the first ultraclean ventilation systems for surgery. Sir Hugh Howorth and his company developed the first systems to ‘drop’ clean filtered air down onto the patient, and create a flow from the patient and away past the clinical staff, thus sweeping any contamination away from the surgical site. The air is ‘scrubbed’ clean of bacteria and dust by HEPA filters, and chilled below the temperature of the operating theatre, to help it drop down vertically over the patient.
U Introducing
ceiling-mounted lights There is a very obvious issue created for ultraclean ventilation when a ceiling- mounted operating light is introduced. The surgeon has to place the operating light above his head in the clean air, where it forms a major obstruction to the air flow. The lights also get warm, which creates thermal buoyancy, warming the air around the light head, which in turn tries to rise
ltraclean ventilation (UCV) systems were originally developed in the UK to reduce infection rates during hip
was an obvious choice. Brandon Medical designed the first operating lights specifically for UCV applications, and it has been one of our key areas of expertise ever since.
Developing the first operating
Figures 1&2: The temperature probe positioning, and the thermal camera image, during the testing at the University of Giessen in Germany.
against the flow of chilled air from the UCV system. The combination of these two factors leads to turbulence in the clean air flow, and reduces the effectiveness of the UCV in delivering consistently clean air over the surgical site, with a corresponding increase in surgical site infections. Professor Charnley and Sir Hugh Howorth looked for an operating light manufacturer which could develop a low turbulence light for UCV theatres. Brandon Medical already worked with Thackrays, which manufactured the Charnley hip joints. It was also the only British operating light manufacturer, so
lights for UCV theatres The original UCV operating lights were developed by Brandon over 40 years ago, before the advent of computer-aided engineering. Empirical testing was used to develop the best shape of light head to minimise turbulence of the relatively low speed airflow, with the light head set in different positions and at different angles, as it would be during surgery. Empirical tests were undertaken to measure and minimise the turbulence of the lights in every position. Finally, a set of design rules were created for the best shapes which can be used to design suitable airflow lights. At the time of the development, all operating lights used incandescent light sources – generally tungsten halogen – which creates a considerable amount of heat. In order to achieve the best shape and an effective thermal design, a reticulated design was necessary (pods mounted in a space frame). A reticulated design has a much higher surface area than single cupola design, allowing for a lower surface temperature and fewer heating issues. Lights with a cruciform or torroidal design (‘doughnut’ shape) also increase the surface area, but create a larger flow impediment.
Although reticulated lights have been used in UCVs for many years, and can be made to work very well, they are harder to wipe clean after surgery. LED is now the default light source for operating lights, and the considerable increase in such lighting’s efficiency has reduced the heating problem considerably, making it
Health Estate Journal 31September 2016
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