Respironics bilichek, User Instruction Manual

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ENGLISH
The light reflected from the skin of neonates and collected by the Bili Chek is analyzed with a highly sophisticated,
proprietary algorithm to generate a serum bilirubin measurement. The major skin components (figure 1) which impact
the spectral reflectance in newborns are (1) dermal maturity, (2) melanin, (3) hemoglobin, and (4) bilirubin. The
intensity of the reflected light is converted to absorbance units, Optical Density (OD), for analysis. The total OD at
each measured wavelength is equal to the sum of the component ODs. This is represented mathematically as:
OD
total
= OD
derm
+ OD
mel
+ OD
heme
+ OD
bili
By utilizing known spectral characteristics of each component, the contribution to the total OD can be sequentially
subtracted until bilirubin is all that is remaining.
FIGURE 1
Non-Invasive Skin Spectral Components
1
1
Jacques, S., Saidi, I., Ladner, A., and D. Oelberg. Developing an optical fiber reflectance spectrometer to monitor bilirubinemia in neonates.
Each of these components have also been considered in the development of the algorithm by which the Bili Chek
computes the bilirubin measurement. By measuring the intensity of the reflected light at more than 100 individual
wavelength bands across the visible spectrum, a spectral analysis can be performed. By normalizing against a
reference standard, the Bili
Cal ™, the variations over time of the bulb and the photo-detectors are eliminated. The peak
absorption of the bilirubin at approximately 460nm is measured by subtracting the absorption of the other components
from the total skin absorption. This is represented by the equation below.
OD
bili
= OD
total
- OD
mel
- OD
heme
- OD
derm
The absorption of light by a molecule is proportional to its concentration. Therefore, the absorption of bilirubin, as
calculated above, is proportional to the concentration of bilirubin in the subcutaneous capillary beds and subcutaneous
tissue. By subtracting the contribution of the aforementioned components, the bilirubin absorbance can be quantified and
is correlated to the laboratory total serum bilirubin levels.
Non-Invasive Skin Spectral Components
1
1
SPIE Proceedings 2975, Laser-Tissue Interactions , San Jose, CA Feb. 1997. 1-7.
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