Lighting
possible to design operating lights with low thermal buoyancy, that are also easy to clean.
Proving suitability
One of the issues in demonstrating the suitability of operating lights for use in UCVs is the lack of available standards. The effectiveness of the original design was proven by measurements of airflow with the lights mounted in a Howorth UCV system. The measurements tested the airflow in the UCV airflow, and smoke tests were carried out to visually check for turbulence.
The UK standard governing UCV systems is HTM 03, which sets out an initial performance test to demonstrate that the UCV ceiling can achieve the minimum airflow across the whole of the ‘sterile’ zone. This is undertaken by marking out a 1 m grid on the floor under the UCV ceiling, and taking airflow measurements at 1 m intervals. However, the test is undertaken without any obstructions, with the operating table and operating lights removed. The HTM 03 test only tests the UCV as a standalone system, and ignores the turbulence that will be introduced when an operating light is fitted.
The only assistance as regards operating lights in HTM 03 is advice that reticulated or cruciform operating lights should be considered for use in UCV theatres. This is of little help to the designer of operating lights, as there is no objective test or standard to test to.
Tested in ‘real life’ situations Brandon Medical’s solution was to test its lights in ‘real life’ situations. A partner was sought to perform scientific testing of the effectiveness of combinations of UCV ceilings and operating lights during live surgery. The University Hospital of Oslo (Rikshospital) had two adjacent, brand new UCV theatres, and was carrying out
Figure 3: Turbulence – Quasar eLite 60. 22 44 49 25 4
41 50 53 5 9 39 38 38 43 7
60 30 0
42 60 60 23 3 –30 14 15 16 6 12 –60 –60 º30 0 30 60 Coordinates
Figure 4: Parameters – Quasar eLite 60. Test Report
Average
Standard Deviation Coefficient of variation Minimum
Boost 50 cms above Boost 150 cms below
32 Health Estate Journal September 2016
research into new UCV systems, so was the ideal partner. Rikshospital used four particle counters in each theatre to measure cfus (colony-forming units) at four points under the UCV ceiling during live surgery, with up to 11 clinical staff in the theatre. Brandon Medical’s Galaxy range of reticulated operating lights were tested in one theatre, and conventional lights from another manufacturer in the adjacent theatre. The results, which were widely published in academic journals, clearly demonstrated the suitability of the reticulated lights, and the poor performance of conventional operating lights, to the theatre environment. The Rikshospital results were corroborated in the laboratory in controlled conditions by installing them in the test laboratory at Weiss Klimatechnik in Germany. Here it was possible to make detailed measurements of the airflow conditions with the operating light in every conceivable position relative to the incident airflow, and to prove the suitability of the design.
Expensive and time-consuming However, the investment in cost and time to perform this thorough level of ‘real life’ and scientific testing is too expensive and time-consuming for all manufacturers to follow, so attempts were made to develop
Tu (%0) 31 19 61 3
v (m/s) 0.2
0.07 34
0.10
No No
T-zu (°C) 20.6 0.23 1
20.3
a quantitative test. The majority of operating light manufacturers are located in Germany, so they led the way in developing a measurement of suitability, resulting in a measurement called the ‘Laminar Flow Index’. Two different theoretical models of Laminar Flow Index were developed, resulting in formulae that can be applied to any operating light, but they were ‘skewed’ towards the German manufacturers’ designs. Neither of the Laminar Flow Index models was adopted by a recognised national or international standards body, as there was a lack of independent evidence that the Laminar Flow Index was a good measure of suitability of lights for UCV.
A proper standard at last It has taken a long time, but at last there is a standard for testing the suitability of operating lights for UCV theatres, DIN 1946 Part 4 (12-2008). It was originally proposed in draft format in 2008, and is now published. Although it is a German national standard, it can be treated as advisory in much the same way as our own HTMs. The advantage is that it is a recognised and regulated national standard that gives a clear ‘pass’ or ‘fail’ result for the suitability of operating lights for UCV theatres. It also provides a quantitative measure for the turbulence
Figure 5: Turbulence – Quasar eLite 30. 20 44 29 8 3
39 67 51 21 5 49 60 29 24 5
–60 –30 0 30 60 Coordinates
60 30 0
16 27 14 8 6 –30 5 4 6 11 6 –60
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