Technology; Technology Of The Inspectra Sto Tissue Oxygenation Monitor - Hutchinson Technology InSpectra StO2 650 Manual Del Usuario

Technology of the InSpectra StO Tissue Oxygenation Monitor
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The InSpectra StO Tissue Oxygenation Monitor makes use of the characteristic light absorption properties
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of hemoglobin in the near infrared wavelength range. Near infrared spectroscopy (NIRS) relies on the relative
transparency of living tissue to light in the 650–1000nm wavelength range. The InSpectra StO Tissue
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Oxygenation Monitor measures tissue optical attenuation values at 680, 720, 760, and 800nm.
The light in the optical cable contains the four wavelengths of light used for the InSpectra
StO System
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Measurement. The maximum depth of the tissue volume sampled is estimated to equal the distance between the
sensor's send and receive fibers. Cui, Kumar, and Chance (1991) confirmed that the mean measurement depth
into the tissue is half of the sensor spacing. The 15mm InSpectra StO Sensor is designed to measure the
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proper depth of the tissue sampled in the thenar eminence.
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There are two (2) light points on the face of the optical sensor , which send and
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receive the signal from the patient's tissue. The comparison of the receive signal
from the patient and the receive feedback signal within the monitor is processed
into a second derivative attenuation spectrum using a fixed wavelength gap point
difference calculation. The resultant second derivative attenuation spectrum is
sensitive to deoxyhemoglobin and oxyhemoglobin absorption. The absorption
figure 21.1
spectrum of light re-emitted from a tissue sample varies mainly with oxyhemoglobin
and deoxyhemoglobin concentration; other chromophores have less effect.
Figure 21.2 illustrates inverted second derivative absorbance curves for hemoglobin at varying oxygen saturation.
Percent InSpectra StO
System Measurements
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calculate the hemoglobin oxygen saturation of blood
contained in the volume of tissue illuminated by near
infrared light. Currently, no measurement standard exists oxyhemoglobin
for measuring tissue hemoglobin oxygen saturation. A
second derivative technique is used in order to quantify
tissue hemoglobin oxygenation (StO ).
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The second derivative spectral measurements at
deoxyhemoglobin
720nm and 760nm are converted into a scaled second
derivative spectrum value (2D720) using the 760nm
measurement as the denominator within the calculated
Wavelength (nm)
ratio. The second derivative algorithm method is insensitive
figure 21.2 Second derivative absorbance curves for
to large changes in optical scattering. An empirically hemoglobin at varying oxygen saturation.
derived calibration curve, which relates the scaled second
derivative calculated value to the displayed percent
InSpectra StO
Measurement, is stored within the device.
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