Lighting for caregivers in the neonatal intensive care unit Mark Rea, PhD Department of Cognitive Science, Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street Troy, NY 12180, USA The primary aim of this article is to define good lighting for caregivers (both medical staff and families) working in the hospital neonatal intensive care unit (NICU) and other areas associated with the critical care environment. Defining good lighting requires understanding that lighting is not only important for the infants in the NICU but also plays significant roles for adults in the NICU [1,2]. First, lighting supports visual processes (eg, acuity, color vision, visual perform- ance). Second, lighting affects circadian regulation (eg, alertness, sleeping, hormone production). Finally, lighting communicates a message to professional staff as well as parents and visitors about the level of care and sophistication provided by the hospital. By thoughtfully addressing all three roles, the lighted environment in the NICU can support the productivity and wellbeing of the professional staff, the health and safety of patients, as well as the profitability of the NICU. A secondary aim of this chapter is to provide practical guidance to health care professionals on how to articulate good lighting objectives to application engineers and designers responsible for the lighting in the NICU. Terminologies and technologies A variety of lighting technologies can be found in the NICU. A basic lighting vocabulary will help the health care professional discuss and achieve good lighting in cooperation with application engineers and designers. For more complete discussions of the following selected terms, consult the IESNA Lighting Handbook [3] or the Lighting Research Center website (www.lrc.rpi.edu/). The amount of light incident on a surface is known as illuminance. More for- mally, illuminance is the amount of light, or luminous flux, falling on a surface. 0095-5108/04/$ ��� see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.clp.2004.04.012 E-mail address: ream@rpi.edu Clin Perinatol 31 (2004) 229���242

It is measured in lumens per square meter (lux) or lumens per square foot (footcandles). Lumens are radiant power (measured in watts) spectrally weighted to match one type of human visual response to light. Today, illuminance meters are more commonly calibrated in terms of lux rather than footcandles. Because a square meter is about 10 times the area of a square foot, measurements in lux are about 10 times greater than measurements in footcandles for the same illumi- nance (1 footcandle = 10.76 lux). The brightness of objects is measured in terms of luminance. Luminance is the product of illuminance and the reflectance of the object toward an observer. The same illuminance on a white piece of paper and the black ink on that paper, for example, will produce two different luminances. Luminance is nearly always measured in lumens per solid angle along the line of sight, per square meter, known as nits or candelas per square meter. The Imperial unit for luminance, the footlambert, is almost never used today. Relative brightness, or luminous contrast, is based on relative luminance specifically, luminous contrast is the difference between the background luminance and the target luminance, divided by the background luminance. Black ink on white paper produces a high contrast target, whereas the same black ink on dark paper will produce a low contrast visual target. Low contrast targets need high light levels to be seen clearly, but medium to high contrast targets do not require as much light. Similarly, small targets need high light levels to be seen, whereas medium to large objects do not. Color rendering is usually defined in terms of the inherent ability of a light source to make colored objects appear natural or realistic. The lighting industry measures the color rendering of the light emitted by a lamp in terms of color rendering index (CRI), which ranges from 100 (best) to zero, and even lower. CRI values of 80 or above are considered excellent for making colored objects appear natural. Modern fluorescent lamps, the most common light source used in health care facilities, usually meet or exceed this value. The color of the light itself affects the general appearance of a space. So-called ������cool������ light sources, such as daylight from a north-facing window, produce bluish-white illumination. ������Warm������ light sources, such as incandescent lamps, produce yellowish-white illumination. The color of the illumination produced by a light source is described in terms of correlated color temperature (CCT) and is measured in degrees Kelvin (K). Commercially available cool light sources range from 5000K to 6500K warm light sources range from 2700K to 3000K. Light sources producing light with color temperatures between 3000K and 5000K are generally termed ������neutral������ in color. Cool light sources are generally associated with institutional lighting, whereas warm light sources are associated with home environments, but this generalization is not universal. Glare comes in several forms. Disability glare reduces the apparent contrast of objects in the field of view due to scattered light within the eye. When scattered light is extreme or the object is inherently of low contrast, visual targets can become invisible. Disability glare is especially important to older people who have clouded preretinal optical media, most notably due to changes in the crystalline lens. Discomfort glare, on the other hand, is an uncomfortable feeling M. Rea / Clin Perinatol 31 (2004) 229���242 230