Innokas Yhtyma Oy VC150 User Manual
7-12
VC150 Vital Signs Monitor
KO00065K
GE TruSignal SpO
2
: GE TruSignal enhanced SpO
2
TruSignal SpO
2
measurement characteristics
The TruSignal pulse oximetry measurement uses a two-wavelength pulsatile
system - red and infrared light - to distinguish between oxyhemoglobin (O
system - red and infrared light - to distinguish between oxyhemoglobin (O
2
Hb)
and reduced hemoglobin (HHb).
The light is emitted from the oximeter sensor, which contains the light source
and a photodetector.
and a photodetector.
The light source consists of red and infrared light-emitting diodes (LEDs).
The photodetector is an electronic device that produces an electrical current
proportional to incident light intensity.
proportional to incident light intensity.
The two light wavelengths generated by the LEDs are transmitted through the
tissue at the sensor site and are modulated by arterial blood pulsation. Since
other fluids and tissues present generally do not pulsate, they do not modulate
the light. The pulsatile portion of the incoming signal is used to detect and isolate
the attenuation of light energy due to arterial blood flow.
tissue at the sensor site and are modulated by arterial blood pulsation. Since
other fluids and tissues present generally do not pulsate, they do not modulate
the light. The pulsatile portion of the incoming signal is used to detect and isolate
the attenuation of light energy due to arterial blood flow.
Figure 7-1. Comparative light absorption
The photodetector in the sensor converts the light intensity information into an
electronic signal. Since O
electronic signal. Since O
2
Hb and HHb absorb different amounts of the light that
is emitted from the oximeter sensor, different amounts of light reach the
photodetector at the selected wavelengths. The electronic signal varies
according to which light source is “on” (red or infrared) and the oxygenation of
the arterial hemoglobin. This information is used to calculate the relative
percentage of O
photodetector at the selected wavelengths. The electronic signal varies
according to which light source is “on” (red or infrared) and the oxygenation of
the arterial hemoglobin. This information is used to calculate the relative
percentage of O
2
Hb and HHb.
Ab
sorption
Time
Variable absorption (due to arterial pulse)
Arterial blood absorption
Venous blood absorption
Other tissue absorption