C
haPter
1
Introduction
The FORE-SIGHT ELITE Absolute Tissue Oximeter is a non-invasive device that measures
absolute tissue oxygen saturation. It operates on the principle that blood contains hemoglobin
in two primary forms — oxygenated hemoglobin (HbO
2
) and de-oxygenated hemoglobin (Hb) —
which absorb near-infrared light in different, measurable ways.
Tissue oxygen saturation (StO
2
) levels are determined by the ratio of oxygenated hemoglobin to
total hemoglobin at the microvascular level (arterioles, venules, and capillaries) in the region to
which the Sensor is applied:
The FORE-SIGHT ELITE incorporates CAS Medical Systems’ exclusive technology to project
harmless near-infrared light (in five precise wavelengths) through the scalp and skull and into the
brain via a disposable Sensor on the patient’s forehead. Reflected light is captured by detectors
positioned on the Sensor for optimal signal collection. After analyzing the reflected light, the
FORE-SIGHT ELITE displays the cerebral tissue oxygen saturation level on the Oximeter as an
absolute number and provides a graphical representation of historical values.
A pulse oximeter only reflects arterial blood oxygen saturation (SpO
2
) and requires pulsations to
operate; whereas, FORE-SIGHT ELITE measures even in pulseless conditions and displays the
balance of oxygen supply & demand in a target tissue (StO
2
), e.g., brain, abdomen, limb muscle.
Thus, FORE-SIGHT ELITE StO
2
values indicate overall tissue oxygenation state, which provides
direct feedback for guiding care interventions.
%StO
2
=
Oxygenated Hemoglobin
=
HbO
2
x 100
Total Hemoglobin
HbO
2
+ Hb
PN 21-22-3000 Rev 07
1
