Standardized bench method for evaluating the efficacy of phototherapy devices

Vreman, H J; Wong, Ruby M.; Murdock, JR; Dk, Stevenson

doi:10.1111/j.1651-2227.2007.00631.x

Cited by 41 publications

(46 citation statements)

References 22 publications

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“…Therefore, it was recently suggested that a high hematocrit/hemoglobin level could reduce the therapeutic efficacy of phototherapy (26). In a post hoc analysis of hemoglobin data from our patients, we found a significant negative correlation between Hb and photoisomer formation during the early phase of phototerapy (15,30, and 60 min), which disappeared at the later time points. This fits with the fact that a difference only exists until an equilibrium between Z,E-and Z,Z-bilirubin is achieved.…”

Section: Discussionmentioning

confidence: 69%

“…The efficacy of phototherapy depends on the irradiance and wavelength of the light, and on the irradiated skin area (3,14). The efficacy of phototherapy is also influenced by bedside optimization of spectral power (e.g., using reflecting surfaces), patient characteristics, and the phototherapy device characteristics (15). The 2004 American Academy of Pediatrics guidelines on management of neonatal jaundice defined intensive phototherapy as irradiance higher than 30 μW/cm 2 /nm over the 430-490 nm wavelength interval (16).…”

Section: Discussionmentioning

confidence: 99%

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Early formation of bilirubin isomers during phototherapy for neonatal jaundice: effects of single vs. double fluorescent lamps vs. photodiodes

et al. 2015

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Background:In neonatal jaundice, phototherapy converts bilirubin to more polar photoisomers which can be excreted without conjugation. We measured changes in the concentration of bilirubin Z,E-photoisomer during the first 4 h of intensive phototherapy using single fluorescent lights as a reference, compared to double fluorescent lights, and a single unit of photodiodes. Methods: Neonates (N = 42; birth weight: 1,200-4,690 g; gestational age: 28-42 wk) were studied during phototherapy. Infants were randomized to: (i) single, or (ii) double fluorescent phototherapy; or (iii) single unit photodiodes. Irradiance was measured. Serum bilirubin (by cooximetry) and Z,E bilirubin (by high-pressure liquid chromatography) were measured at 0,15, 30, 60, 120, and 240 min after the start of phototherapy. Data were analyzed with a linear mixed model. results: There was a highly significant increase of Z,E-bilirubin over time (P < 0.0001), starting at 15 min. Photoisomers reached ~25% of total bilirubin concentration after 4 h. However, there were no significant differences between the three randomized groups in spite of significantly higher irradiance using double fluorescent lights vs. single fluorescent or photodiodes. conclusion: Formation of bilirubin photoisomers is rapid, and occurs early during intensive phototherapy for neonatal jaundice. The rate and level of photoisomerization was not influenced by irradiance and light source. P hototherapy is the standard treatment for hyperbilirubinemia in newborns, and is administered to prevent kernicterus and other sequelae of bilirubin neurotoxicity (1).It is effective and considered safe. However, a recent report suggests that "aggressive" phototherapy in the smallest infants of birth weight 501-750 g may be associated with increased risk of death (2).When native bilirubin IXα (Z,Z) in neonates is exposed to light, a rapid photochemical reaction produces water-soluble configurational (4Z,15E; 4E,15Z; 4E,15E) and structural (Z-lumirubin; E-lumirubin) isomers (3,4). Photooxidation may also occur (5,6). Due to increased polarity, these isomers can be excreted in bile and urine, bypassing the need for conjugation. It has recently been suggested that these isomers, because of their polarity, should be less able to cross the bloodbrain barrier (1,7). If this is correct, photoisomer formation might be directly neuroprotective, irrespective of the effect on excretion. Experimental data suggest that bilirubin photoisomers are less toxic than the native IX α (Z,Z), but there are methodological weaknesses in these studies (1). Thus, experimental proof of the hypothesized direct neuroprotective effects of photoisomerization is still needed. Both different light qualities and variable light irradiance are commonly employed in practical phototherapy. Herein we have investigated whether such factors may impact on photoisomer formation.The common light sources used in phototherapy are either fluorescent, or tungsten-halogen lamps with wide emission spectrum, or light-emitting diodes (LEDs) wi...

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Section: Discussionmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 99%

Early formation of bilirubin isomers during phototherapy for neonatal jaundice: effects of single vs. double fluorescent lamps vs. photodiodes

et al. 2015

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“…Emission spectra of various blue LEDs with peak wavelengths in the 400-500 nm range are nearly symmetric around their peaks with bandwidths of 25-30 nm (21,(41)(42)(43). The spectrum of the LEDs used here (460 nm peak and 28 nm bandwidth) was from that reported from a commercially available and widely used phototherapy system (41,42).…”

Section: Impact Of Quantity and Concentrationmentioning

confidence: 99%

“…The spectrum of the LEDs used here (460 nm peak and 28 nm bandwidth) was from that reported from a commercially available and widely used phototherapy system (41,42). The relative intensity at every 2 nm was incorporated into the database.…”

Section: Impact Of Quantity and Concentrationmentioning

confidence: 99%

The effect of hematocrit on the efficacy of phototherapy for neonatal jaundice

et al. 2013

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Background:The therapeutic phototherapy action spectrum ranges from 420 to 500 nm. However, a recent report of improved efficacy of fluorescent "turquoise" light (~490 nm) as compared with blue light (~450 nm) underscores the need to define an optimal action spectrum for precision-targeted phototherapy using very narrow wavelength ranges. Methods: We used a current semi-empirical model of the optical properties of skin for robust calculations of the fraction of light absorbed by bilirubin at various wavelengths that could be confounded by hemoglobin (Hb), melanin, and skin thickness. Applying assumptions regarding the wavelength dependence of bilirubin photochemistry, "action spectra" were assembled from the calculated values. results: All the calculated action spectra displayed a peak between 472 and 480 nm (most at 476 nm), which is a significant shift from the well-reported 460 nm absorption peak of bilirubin. Of note, the relative amplitudes of the action spectra showed an inverse relationship with hematocrit (Hct). conclusion: We speculate that a narrow range of light at 476 nm would be 60% more effective than blue (broadband) fluorescent lamps. Because Hb serves as a major competitor of bilirubin for light absorption, the calculations also predict that the efficacy of phototherapy is dependent on the Hct. A high Hct could reduce therapeutic efficiency. a n in vivo model to better define the optimal wavelength range for precision-targeted phototherapy has been elusive. Advances in understanding of skin optical properties have provided an optical model of neonatal skin in the therapeutic range (400-520 nm) that allows facile calculation of the influences of skin structure, melanin pigmentation, and cutaneous hemoglobin (Hb) on the action spectrum for phototherapy. Of these, Hb absorbs most of the visible light in the skin (1,2). As a result, competition from Hb with bilirubin for light should strongly affect the wavelength region of light that is most effective for phototherapy of neonatal jaundice. Although Hb competition has been recognized and used, in part, to predict the action spectrum for phototherapy (3,4), explicit reference to Hb competition appears to be absent from the recent literature. The reports of clinical studies showing that blue-green or green light may be more effective than blue light (5,6) generally rationalize these observations on the general notion that the longer wavelengths "penetrate deeper into the skin" without specific reference to Hb absorbance.Furthermore, significant competition for light by skin Hb also implies that the hematocrit (Hct) may in turn affect the efficacy of phototherapy. This possibility was recognized in 1974 by Lucey and Hewitt (7), who conjectured that the Hct "may be a contributing factor to the differences in response of serum bilirubin to light that one observes in different infants. " They observed in in vitro irradiation studies that changes in the Hct affect diazo-reactive bilirubin disappearance in blood. Almost a decade elapsed before a clinical st...

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“…Thus, it is becoming increasingly important that devices be evaluated for their physical and spectrophotometric characteristics as well as their clinical efficacy to affect the photochemical alteration of bilirubin (BR) in the newborn skin and circulation. The study reported by Subramanian, et al [4] in this issue of Indian Pediatrics significantly adds to the efforts that have already been made towards this goal [5][6][7], while it also demonstrates the diversity of traditional and new technologies.…”

Section: E D I T O R I a L E D I T O R I A L E D I T O R I A L E D I mentioning

confidence: 99%

Evaluating the efficacy of phototherapy devices

Vreman

2011

Indian Pediatr

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Standardized bench method for evaluating the efficacy of phototherapy devices

Cited by 41 publications

References 22 publications

Early formation of bilirubin isomers during phototherapy for neonatal jaundice: effects of single vs. double fluorescent lamps vs. photodiodes

Early formation of bilirubin isomers during phototherapy for neonatal jaundice: effects of single vs. double fluorescent lamps vs. photodiodes

The effect of hematocrit on the efficacy of phototherapy for neonatal jaundice

Evaluating the efficacy of phototherapy devices

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