LED Surgical Task Lighting

BUILDING TECHNOLOGIES PROGRAM

Technical Guidance Document: LED Surgical Task Lighting

The U.S. Department of Energy’s (DOE) Hospital Energy Alliance (HEA) brings together leading hospitals and national associations in a strategic alliance designed to improve energy efficiency and reduce greenhouse gas emissions of healthcare systems throughout the country. By lever- aging access to advanced technologies emerging from the national laboratories, HEA members are creating a national forum for the industry to share evidence- based technology solutions and influence the energy performance of medical equipment and systems.

In October 2010, acknowledging rapid LED surgical task light. Photo credit: Steris Corp. improvements in light-emitting diode (LED) technology, the HEA Lighting Project Team selected LED surgical task not require such filtering media, and their gical task lights. LED technology lighting as a project to explore in 2011. A higher efficacy can allow for reductions in may offer additional benefits, including scoping study was completed in January connected load of 50 percent or more, with enhanced mitigation of shadows cast 2011, characterizing the energy-savings potential for additional energy savings by surgical staff, as demonstrated in potential of currently available LED prod- through constant-color dimming and Figure 1.ii Some products even allow for ucts relative to tungsten-halogen (halo- reduced cooling load in the operating room. color adjustment. At present, however, gen) and high-intensity discharge (HID) Furthermore, while halogen lamps are typi- independent test data are generally not benchmarks.i This fact sheet was subse- cally rated for just 1,000 to 3,000 hours and readily available, performance in the later quently developed to provide objective fail catastrophically (sudden and without years of the product’s lifetime can only guidance to hospital owners and manag- warning), LED surgical task lights are be estimated, and products are relatively ers seeking to acquire high-performance generally rated for 25,000 to 40,000 hours expensive on a first-cost basis. Thorough LED surgical task lights. and are expected to “fail” by gradually product specification and evaluation are fading in brightness. Table 1 summarizes essential for a successful LED surgical Why Use LEDs for Surgical some of the primary benefits of LED sur- task lighting project. Task Lighting? LED technology is advancing into new cat- Table 1. Potential Advantages of LEDs egories of white light applications, including Parameter Benefit surgical task lighting, where early indica- tions suggest significant potential for energy Efficacy LEDs require less wattage to produce equivalent light levels. savings and reduced maintenance. The Heat in Beam Substantial thermal energy must be conducted away from LEDs, but halogen lamps typically used in surgical they radiate relatively little ultraviolet (UV) or infrared (IR) energy. task lights suffer from relatively low lumi- Dimmability Although system compatibility must be verified on a case-by-case basis, nous efficacy (lumens of light output per LEDs may offer dimming without color shift or flicker, thereby yielding watt of input power), which is only wors- additional energy savings. ened by filters that must be used to reduce the amount of non-visible radiation they Maintenance LEDs promise significantly greater life and a non-catastrophic failure mechanism. emit. LED surgical task lights typically do TECHNICAL GUIDANCE DOCUMENT: LED SURGICAL TASK LIGHTING 2

the second edition of the standard. Many to supplement CCT, thereby limiting such product datasheets have not been updated color variation.vii since the standard was revised, so com- parison between product ratings must be The NEMA/ANSLG standard simplifies performed with care to ensure manufac- specification of chromaticity, with allow- turers are consistently reporting depth of able measured Duv values ranging from illumination based on the current edition. -0.006 to 0.009 as a function of nominal CCT. Table 2 demonstrates that the NEMA/ Some IEC criteria provide fixed minimum ANSLG criteria are more stringent than the requirements or maximum restrictions, IEC criteria. The red text indicates five of 2 Figure 1. Shadow Dilution such as the 1000 W/m limit for total irra- the six IEC boundary points fall well out- diance. Other criteria provide ranges of side NEMA/ANSLG tolerances for white Photo credit: Cleveland Clinic acceptable values. For example, major light, suggesting the need for evaluation Industry Standard surgical luminaires (task lights or lamp- of Duv in addition to the IEC criteria for Performance Metrics heads) and surgical luminaire systems CCT and chromaticity coordinates. (having multiple lamp-heads) must pro- The U.S. Food and Drug Administration duce 40,000 to 160,000 lux of central illu- Similarly, the General Color Rendering (FDA), which grants marketing clearance minance. Because the value required by Index (CRI or Ra) may not provide an for medical devices, issued product testing surgical staff may fall anywhere within adequate measure of the ability of a light iii guidance in 1998 for surgical task lights. this wide range, specifications should source to enable color discrimination. This guidance encouraged adherence to the establish a set of narrower sub-ranges, CRI measures color fidelity of the test International Electrotechnical Commission where each sub-range is tailored to the source when lighting a set of pastel- (IEC) draft standard 60601-2-41, the second requirements of the associated surgical colored objects, relative to a reference iv edition of which was published in 2009. procedure. The number of lamp-heads source (incandescent or daylight depend- Many of the IEC criteria closely resem- should be determined in advance, since ing on CCT). Supplementing CRI, the ble criteria offered by the Illuminating together they must not exceed 160,000 lux. Special Color Rendering Index R9 evalu- Engineering Society of North America ates the ability of a source to render a (IESNA or IES) in Section 4.11 of its Color Characteristics saturated red object (having peak reflec- American National Standard, which have tance from 745 to 805nm), but it is not remained essentially unchanged since 1995.v The IEC criteria for correlated color tem- clear whether these two metrics together perature (CCT) and chromaticity coordi- provide an adequate measure of color The IEC criteria are currently used by FDA nates also require greater specificity. Two rendition in surgical lighting applications. Accredited Persons performing third- light sources of equivalent CCT are gen- party inspection of surgical task lights.vi erally expected to have equivalent color The Color Quality Scale (CQS) was devel- Considering existing protocol and the rel- appearance, with both being yellowish- oped by the National Institute of Standards atively high cost of testing products in this white, bluish-white, or something in and Technology (NIST) as an alternative category of medical equipment, it is rec- between. But if their chromaticity coordi- to CRI, after studies found CRI did not ommended that the IEC criteria continue to nates do not lie near the Planckian locus, correlate well with color preference for serve as the basis for product specifications. they can appear greenish or pinkish in color. some light source types, including LEDs.viii However, the IES recommendations merit The National Electrical Manufacturers CQS is largely modeled after CRI, with consideration, and surgical staff should be Association (NEMA), in cooperation with one major difference being the use of satu- surveyed to identify any refinements needed the American National Standard Lighting rated colors in lieu of pastels. Surgical staff to satisfy the requirements of various sur- Group (ANSLG), defined the Duv metric may wish to perform field investigations gical procedures. Additionally, in retrofit or upgrade applications, existing equipment 1 should be audited to provide an accurate Table 2. IEC Chromaticity Boundaries measure of baseline performance. Such an IEC point x coord. y coord. CCT (K) Duv audit could uncover any deterioration of A 0.310 0.375 6355 0.026 the UV-IR filters used for halogen products. B 0.310 0.307 6886 -0.007 The IEC standard provides definitions for a C 0.341 0.307 5006 -0.023 number of terms used herein. Note that D 0.420 0.370 3008 -0.012 “depth of illumination” was originally E 0.445 0.422 3010 0.006 defined by the IEC as the combined distance upward and downward to points at F 0.380 0.422 4289 0.020 20 percent of the central illuminance, but this value was changed to 60 percent in 1Software allowing calculation of CCT and Duv from chromaticity coordinates is available upon request from Yoshi Ohno at NIST. TECHNICAL GUIDANCE DOCUMENT: LED SURGICAL TASK LIGHTING 3

to determine whether CQS offers any output should be established with an under- • Depth of illumination shall be no less

advantages over the CRI and R9 metrics. standing of benchmark (halogen) lumen than [specify value] and no greater than maintenance. For example, if a given [specify value], or adjustable across Another potential concern is that some sur- LED light-head initially produces this range. gical task lights may produce color varia- 125,000 lux and its rated useful lifetime • Rated useful lifetime, defined as the tion across the surgical field. This would is based on the hours of operation to 80 not be evident from test data, and could hours of operation at greater than 80 percent of initial output (L80), then it would occur when an LED surgical task light percent of initial light output, shall be be a suitable replacement for a halogen no less than [specify value] hours. incorporating LEDs of more than one nom- light-head initially producing 105,000 lux. inal CCT is partially obstructed by surgi- • Dimming, if implemented, shall not cal staff. Ultimately, the color quality of a Specifying Products compromise the above criteria or cause surgical task light is best judged visually by excessive flicker, harmonic distortion, surgical staff, and in a mock-up scenario Requirements will vary between hospitals or electromagnetic interference. whereby the surgical task light is used to and even between surgical suites, so a illuminate a realistically simulated patient. recommended specification structure is Note that while DOE recommends IES offered here in lieu of recommended crite- LM-79 testing for most LED lamps and Lifetime Characteristics ria. The italicized text in brackets should luminaires, this methodology cannot be be replaced with values determined after applied to most surgical task lights for Although the lifetime of other compo- existing equipment has been audited and characterization of luminous intensity.xiii nents (such as power supplies) should be surgical staff have been surveyed: Far-field goniophotometry would not considered, LED useful lifetime is typically capture the near-field convergence and defined as the hours of operation until light • Input power, including power supply losses, shall not exceed [specify value] W. subsequent divergence of the beam of output depreciates to some percentage light, as illustrated in Figure 2. In addi- of initial output. A value of 70 percent is • Central illuminance shall be no less than tion, knowledge of total initial light out- often used in architectural applications, [specify value not less than 40,000] lux, put (lumens) would be of limited value or dimmable to this value. denoted L70. Meanwhile, IEC stipulates in this application. that light output “shall not vary by more • Central illuminance shall be no greater than 20 percent during use,” with compli- than [specify value not greater than ance to be verified after 10 days of cycled 160,000] lux. operation. • Remaining illuminance shall be no IES LM-80 provides a standard method for less than long-term testing of lumen (brightness) –– [specify value] percent with maintenance for LED light sources, but one mask this method is not applicable to complete –– [specify value] percent with luminaires (such as surgical task lights) two masks without consideration of case temperature –– [specify value] percent with tube and drive current when operated in situ.ix and no mask Furthermore, such data have typically –– [specify value] percent with tube only been collected for the first 6,000 and one mask to 10,000 hours of operation, requiring –– [specify value] percent with tube estimation of lumen maintenance later and two masks. in life. • Nominal correlated color temperature There is currently no standard method of (CCT) shall be no less than [specify extrapolating rated lifetimes from LM-80 value] K and no greater than [specify test data. Until the much-anticipated IES value] K, or adjustable across this range. TM-21 is published, LED luminaire man- • Measured CCT and Duv shall comply ufacturers are free to choose their own with NEMA/ANSLG tolerances for x method of curve-fitting to LM-80 data. white light.

Halogen lamps produce approximately 95 • Measured R9 shall be no less than percent of initial output at 70 percent of [specify value]. their rated life, at which time these cata- • Light field diameter 10d shall be no less strophically failing lamps may be replaced than [specify value] and no greater than as part of a scheduled group-relamping [specify value], or adjustable across Figure 2. Converging-Diverging Beam. xi,xii program. Criteria for initial LED light this range. (Image adapted from Skytron literature) TECHNICAL GUIDANCE DOCUMENT: LED SURGICAL TASK LIGHTING 4

Suggested submittal requirements are –– Central illuminance Ec (lux) and Sharing Experiences then as follows: corresponding measurement distance HEA is a forum in which healthcare –– Percent remaining illuminance with • Submit product datasheet and installa- leaders work together with DOE, its One mask tion instructions. national laboratories, and national build- Two masks • Submit detailed product warranty. ing organizations to accelerate market Tube and no mask adoption of advanced energy strategies • Submit IES LM-80 report and certifi- Tube and one mask and technologies. A primary function cate clearly indicating actual in-situ Tube and two masks and benefit of membership is the ability LED case temperature, actual in-situ –– Correlated color temperature (K) to share experience with new technologies LED drive current, and expected –– Chromaticity coordinates like LED surgical task lights. Similar lumen maintenance at end of rated –– Special color rendering index R9 forums are offered by HEA members, useful life. –– Light field diameter 10d including the American Society for • Submit safety certification and file –– Depth of illumination. Healthcare Engineering (ASHE) and number for Medical Equipment per These criteria and submittal requirements Practice Greenhealth, and additional the National Electrical Code. Testing will facilitate the identification of high- information on LED technology can body shall be a U.S. Occupational quality products backed by trustworthy be found on the DOE SSL program Safety Health Administration test data. website at www.ssl.energy.gov. (OSHA) Nationally Recognized Testing Laboratory (NRTL). Verifying Performance A Strong Energy Portfolio • Product shall be listed on the FDA for a Strong America Lighting systems should be audited before Establishment Registration & Energy efficiency and clean, renewable and after any retrofit or upgrade. Existing Device Listing.xiv energy will mean a stronger economy, a luminaires should be cleaned, relamped and cleaner environment, and greater energy • Submit test report from an FDA properly seasoned before any measurements independence for America. Working with Accredited Person for third-party are made. Measurement equipment should a wide array of state, community, industry, inspection indicating compliance be selected for appropriate range and accu- and university partners, the U.S. Department of Energy’s Office of Energy Efficiency and with IEC 60601-2-41, clearly indicat- racy, in accordance with the IEC standard. ing the following measured values: Renewable Energy invests in a diverse The performance of LED surgical task lights portfolio of energy technologies. –– Input power (W) including power should also be monitored periodically over supply losses time to ensure continued safe operation, and to see that lifetime claims are fulfilled for these relatively expensive products.

i Tuenge, JR. “LED Surgical Task Lighting Scoping Study: A Hospital Energy Alliance Project.” Pacific Northwest National Laboratory, Richland, WA. January 2010. ii “The Best and the Brightest—Choosing the Top LED Surgical Lights.” Health Devices, Volume 39, Number 11. ECRI Institute, Plymouth Meeting, PA. November 2010. iii “Guidance Document for Surgical Lamp 510(k)s—Guidance for Industry, FDA Reviewers/Staff and Compliance.” U.S. Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health, General Surgical Devices Branch, Division of General and Restorative Devices, Office of Device Evaluation, Washington, DC. July 1998. iv IEC Subcommittee 62D, Electromedical Equipment. IEC 60601-2-41 Edition 2.0, “Medical Electrical Equipment, Part 2-41: Particular Requirements for the Safety of Surgical Luminaires and Luminaires for Diagnosis.” International Electrotechnical Commission, Geneva, Switzerland. August 2009. v IESNA Committee for Health Care Facilities. ANSI/IESNA RP-29-06, “An IESNA Recommended Practice—Lighting for Hospitals and Health Care Facilities.” Illuminating Engineering Society of North America, New York, NY. 2006. vi Third-Party Inspection (Devices) Accredited Persons Inspection Program. U.S. Food and Drug Administration. Accessed on May 3, 2011, at http://www.fda.gov/MedicalDevices/ DeviceRegulationandGuidance/PostmarketRequirements/ThirdPartyInspection/default.htm. vii American National Standard Lighting Group. ANSI_NEMA_ANSLG C78.377-2008, “American National Standard for Electric Lamps—Specifications for the Chromaticity of Solid State Lighting (SSL) Products.” National Electrical Manufacturers Association, Rosslyn, VA. 2008. viii Davis, W. and Ohno, Y. “Color quality scale.” Optical Engineering Vol. 49(3). SPIE Digital Library. March 2010. ix IES Testing Procedures Subcommittee on Solid-State Lighting. IES LM-80-08, “Approved Method: Measuring Lumen Maintenance of LED Light Sources.” Illuminating Engineering Society of North America, New York, NY. 2008. x IES Testing Procedures Subcommittee on Solid-State Lighting. IES TM-21-11 (draft), “Projecting Long Term Lumen Maintenance of LED Light Sources.” Illuminating Engineering Society of North America, New York, NY. 2011. xi Rea, MS. IESNA Lighting Handbook, 9th edition. Illuminating Engineering Society of North America. New York, NY. June 2000. xii IESNA Maintenance Committee. IESNA/NALMCO RP-36-03, “Recommended Practice for Planned Indoor Lighting Maintenance.” Illuminating Engineering Society of North America, New York, NY. 2003. xiii IES Testing Procedures Subcommittee on Solid-State Lighting. IES LM-79-08, “Electrical and Photometric Measurements of Solid-State Lighting Products.” Illuminating Engineering Society, New York, NY. 2008. xiv Establishment Registration & Device Listing. U.S. Food and Drug Administration. Accessed under product code FSY on May 3, 2011, at http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfRL/rl.cfm.

EERE Information Center For more information, contact: 1-877-EERE-INF (1-877-337-3463) Jason Tuenge www.eere.energy.gov/informationcenter Pacific Northwest National Laboratory [email protected] commercialbuildings.energy.gov

August 2011