Principle Of Operation; Understanding T-Stat ® Readings - Spectros T-Stat 2.0 User Manual

E. Principle of Operation
The basis for operation for the T-Stat
forms (oxy-, deoxy-, met-, carboxy-) has unique spectroscopic properties that allow StO2%
to be determined based on measurements of the spectral characteristics of the reflectance of
light from tissue. The Spectros T-Stat
monitoring to determine the relative amount of oxygenated and deoxygenated hemoglobin
in the microvascular tissue spaces. StO2% is then defined as the percentage of hemoglobin in
the oxygenated form as compared to the total hemoglobin in both oxygenated and
deoxygenated forms. The broadband spectral approach also allows for measurement of
tissue characteristics, ie lipid and water concentration. These characteristics can be used to
make a determination that the site or region where the sensor is placed is in fact looking at
components that comprise normal tissue. The software provides a displayed warning of "no
tissue" when it detects spectral parameters outside normal tissue ranges in order to alert the
doctor to verify the sensor placement.
F. Understanding T-Stat
The T-Stat
several important ways:
Capillary-weighted
Hemoglobin oxygen saturation of blood in the microvascular tissue, is typically lower than
pulse oximetry saturation (SpO
oximetry measures arterial saturation, tissue oxygenation is capillary-weighted, and
estimates the hemoglobin oxygen saturation at the site of tissue oxygen extraction. Tissue
optical saturation is thus responsive to changes in oxygenation of the tissue itself, whether
caused by changes in arterial oxygenation (hypoxemia) or by changes in blood flow
(reduced-flow or no-flow ischemia).
Non-pulsatile
Unlike pulse oximetry, a pulse is not required for the measurement to be made. Therefore, the T-
Stat Tissue Oximeter continues to measure during low-perfusion, hypotension, or asystole.
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Normal Values Differ
Hemoglobin oxygen saturation of blood in the microvascular tissue spaces (StO
runs much closer to venous saturation (SvO
oxygen saturation StO
human use have not been recognized in health and disease, measured and published values
of StO % for many tissues are typically 71% +/- 3%, or a 95% confidence interval of 65%
2
- 77% (see Table 1, below).
Spectros Medical Devices Inc.
T-STAT 2.0 User Manual
®
Readings
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Tissue Oximeter measurements differ from conventional pulse oximetry in
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%) and arterial saturation (SaO
2
% for some tissues has been established. While reference ranges for
2
2.0 Tissue Oximeter is that hemoglobin in its various
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uses broadband, multi-wavelength illumination and
%) than to arterial saturation (SaO
2
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%). Whereas pulse
2
%) typically
2
%). Tissue
2
Rev B