Product Manual

M3B Vital Signs Monitor Service Manual
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2.4.2 SpO
2
SpO
2
is based on the absorption of pulse blood oxygen to red and infrared light by means of
finger sensor and SpO
2
measuring unit. The light-electronic transducer in finger sensor converts
the pulse red and infrared light modulated by pulse blood oxygen into electrical signal, the signal
is processed by hardware and software of the unit. The PLETH curve and numeral value of SpO
2
will be obtained.
By tracing the pulse waveform in the fingertip, using specified arithmetic and consulting the
clinical data table, we can obtain the SpO
2
value. The SpO
2
sensor consists of two LED and a
photodetector. The two LED are respectively red diode and infrared diode, which are lighted on
according to certain time sequence. When the capillary vessel of the fingertip congests repeatedly,
the light of the LED is absorbed by blood vessels and organs and then projected onto the
photodetector. The photodetector can detect the light intensity varying with pulse changes and
display the changing light intensity in the form of changing electronic signals. The ratio between
the DC and AC of the two types of signals for light is the proportion of oxygen in the blood. Then
we can calculate correct SpO
2
value by using specified arithmetic and also calculate pulse rate
according to the SpO
2
waveform.
The SpO
2
module mainly consists of following four parts: sensor, signal processing, control unit
of LED driving sequence, singlechip.
2.4.3 CO
2
The measure of CO
2
is based on infrared absorption characteristic of CO
2
module. CO
2
molecule
can absorb 4.3µm infrared ray. Absorption intensity is proportional to CO
2
concentration of
patient sample, the CO
2
concentration will compute from the detecting CO
2
absorption intensity
of patient sample. The relation between partial pressure and percentage of CO
2
concentration is
given below:
P (mmHg) = Percentage (%) × Pamp (ambient pressure)
There are Mainstream and Sidestream modules according to different connecting way of infrared
sensor.
SideStream measurement takes a sample of the respiratory gas with a constant sample flow from
the patient’s airway and analyzes it with a remote CO
2
sensor. MainStream measurement uses a
CO
2
sensor attached to an airway adapter directly inserted into the patient’s breathing system.
This method is available using the monitor’s built-in CO
2
measurement.
This module can be applied in operation room, monitor units etc, it can measure the CO
2
partial
pressure or concentration of patient Air Way, obtain End tidal CO
2
(EtCO
2
), Inspired minimum
CO
2
(InsCO
2
), Air Way Respiration Rate (AwRR), and display CO
2
concentration waveforms.