Factors That Affect the Dose and Efficacy of Phototherapy

FactorMechanism/Clinical RelevanceImplementation and RationaleClinical Application
Spectrum of light emittedBlue-green spectrum is most effective. At these wavelengths, light penetrates skin well and is absorbed maximally by bilirubin.Special blue fluorescent tubes or other light sources that have most output in the blue-green spectrum and are most effective in lowering TSB.Use special blue tubes or LED light source with output in blue-green spectrum for intensive PT.
Spectral irradiance (irradiance in certain wavelength band) delivered to surface of infant↑ irradiance →Irradiance is measured with a radiometer as μW/cm2 per nm. Standard PT units deliver 8–10 μW/cm2 per nm (Fig 6). Intensive PT requires >30 μW/cm2 per nm.If special blue fluorescent tubes are used, bring tubes as close to infant as possible to increase irradiance (Fig 6). Note: This cannot be done with halogen lamps because of the danger of burn. Special blue tubes 10–15 cm above the infant will produce an irradiance of at least 35 μW/cm2 per nm.
↑ rate of decline in TSB
Spectral power (average spectral irradiance across surface area)↑ surface area exposedFor intensive PT, expose maximum surface area of infant to PT.Place lights above and fiber-optic pad or special blue fluorescent tubes* below the infant. For maximum exposure, line sides of bassinet, warmer bed, or incubator with aluminum foil.
→ ↑ rate of decline in TSB
Cause of jaundicePT is likely to be less effective if jaundice is due to hemolysis or if cholestasis is present.When hemolysis is present, start PT at lower TSB levels. Use intensive PT. Failure of PT suggests that hemolysis is the cause of jaundice. If ↑ direct bilirubin, watch for bronze baby syndrome or blistering.
(↑ direct bilirubin)
TSB level at start of PTThe higher the TSB, the more rapid the decline in TSB with PT.Use intensive PT for higher TSB levels. Anticipate a more rapid decrease in TSB when TSB >20 mg/dL (342 μmol/L).
  • PT indicates phototherapy; LED, light-emitting diode.

  • * Available in the Olympic BiliBassinet (Olympic Medical, Seattle, WA).