1297 A NARROW SPECTRUM LIGHT SOURCE FOR PHOTOTHERAPY

Abstract

The increasing use of phototherapy for the treatment of neonatal jaundice has generated some concern in view of the potential long-term genetic consequences of this therapeutic modality. Our laboratory has determined that light at wavelengths ≤ 450 nm is the portion of the visible spectrum responsible for the in vitro and in vivo DNA-modifying activity of phototherapy. In view of this and subsequent work which has shown that light at wavelengths > 460 nm generate water-soluble bilirubin photoisomers, we have developed a new, portable phototherapy unit in which more than 95% of the spectral emission falls between 460 and 480 nm. The light source is a 5 kilowatt mercury arc lamp which has been doped with metal halides. The light is then passed through a series of three filters which remove all undesired radiation, including infrared. The resulting irradiance is 20 watts/M2 over an area 60 x 45 cm, or 10 times the 460-480 nm spectral output of a standard phototherapy unit (Duro Test, Vita Lite). Using UV-difference spectroscopy to compare the generation of bilirubin photoproducts by these two light sources, we found enhanced photooxidation of bilirubin with the standard phototherapy unit, while the narrow spectrum unit proved more effective in bilirubin photoisomerization. These results demonstrate the feasibility of developing a phototherapy unit devoid of wavelengths with a potential for long-term genetic sequellae yet effective in bilirubin isomerization.