Phototherapy Devices - Basics
| What does "Phototherapy" mean? |
Photo = light Phototherapy = Therapy using light |
| What does it do? |
The phototherapy light shines light onto the baby’s
skin. The light must be the correct wavelength (colour) and
the correct intensity (brightness). It is used for treating
a condition called Jaundice or Hyperbilirubinemia. |
| Physiology |
When red blood cells die and are broken down, a chemical called
“bilirubin” is produced. Normally the bilirubin
is processed by the liver and excreted from the body by the
kidneys in the urine. The baby’s liver sometimes cannot
process the bilirubin quickly enough and it begins to build
up in the blood. Bilirubin is deposited in the skin, whites
of the eyes, and mucous membranes (for example the inside of
the mouth). When this occurs, the baby appears yellow and is
said to be “Jaundiced”. Usually Jaundice disappears
in 1-2 weeks and does not require special treatment. Some bilirubin
in the blood is normal but when the concentration rises too
high it is dangerous hyperbilirubinemia. An excessive level
of bilirubin can lead to serious neurological damage such as
brain damage and hearing loss. |
| How it works |
During phototherapy the baby’s skin is exposed to blue
light (420 – 500nm). The bilirubin deposited in the skin
is “photoisomerised” (changed shape by the light)
and becomes water soluble. This is a similar change that occurs
normally in the liver. The photoisomerised bilirubin then dissolves
back into the blood where it is excreted from the body in urine.
The untreated bilirubin in the blood then deposits in the skin
and the process continues until all or most of the bilirubin
is removed. This happens over a long period of time, usually
several days. The effectiveness of the phototherapy depends on: - the intensity of the therapeutic light - the wavelength (colour) of the light - the surface area of skin exposed Some phototherapy lights use white light instead of pure blue. White light contains all the colours but it is only the blue wavelengths that treat the Jaundice. |
| Units of measurement |
mW/cm2 |
| Typical values |
Wavelength = 420-500 nm (with the most important wavelength
of 470 nm) Intensity = 8 uW/cm2/nm to 25 uW/cm2/nm or 0.65 mW/cm2 to 2 mW/cm2 (with a blue filter of 80nm bandwidth) |
| Picture of equipment |
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 Ohio |
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