Mindray PM-7000, Service Manual

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Chapter 2 Principles
22
pressure can be obtained. For neonates, pediatric and adults, it is necessary to select
the cuffs of a proper size to avoid possible measurement errors. In the NIBP
measurement, there is a protection circuit used to protect patient from over-high
pressure.
The NIBP measurement modes include:
1) Adult/pediatric/neonate mode: To be selected according to the build, weight and age
of the patient;
2) Manual/Auto/Continuous mode: The manual measurement is also called single
measurement; in this mode, only one measurement is done after being started. In the
auto measurement mode, the measurement can be done once within the selected
period, with the interval being 1, 2, 3, 4, 5, 10, 15, 30, 60, 90, 120, 180, 240 or 480
minutes. In the continuous measurement mode, quick continuous measurement will be
done within 5 minutes after being started; it detects the changes in blood pressure
effectively.
2.4.4 SpO
2
The SpO
2
value is obtained through the pulse waves of the finger tips based on specific
algorithm and clinical data. The SpO
2
probe is the measurement transducer. It has two
inbuilt LEDs and an inbuilt light receiver. The two LEDs include one red-light diode and
one infrared diode, which emit light in turns. When the capillaries in the finger tip are
iteratively congested with blood pumped by the heart, the light emitted by the LEDs, after
absorbed by the capillaries and tissue, casts on the light receiver, which can sense, in the
form of electric signal, the light strength changing with the pulsated blood. The DC/AC
ratio of the two photoelectric signals corresponds to the content of the oxygen in the blood.
Therefore, the correct pulse oxygen saturation can be obtained with specific algorithm.
Moreover, the pulse rate can be obtained according to the pulse waveform.
The circuit of the SpO
2
module is involved in four parts: SpO
2
probe, signal processing
unit, LED-driven sequencing control part and the MCU.
2.4.5 TEMP
Temperature measurement principle:
1. The transducer converts the body temperature to the electric signal;
2. The amplifier amplifies the electric signal;
3. The CPU processes the data.
The circuit is a proportional amplifier consisting of operation amplifiers. When the
temperature reaches the heat-sensitive probe, the heat-sensitive probe generates the
voltage signal, which is sent to the A/D converter after being amplified. The probe
detecting circuit is a voltage comparator consisting of operation amplifiers. When the
probe is disconnected, the voltage input is lower than the comparing voltage, so the
voltage comparator outputs the low level; when the probe is connected, the voltage input
is higher than the comparing voltage, so the voltage comparator outputs the high level.
2.4.6 IBP
The IBP module can monitor the arterial pressure, central venous pressure and
pulmonary arterial pressure.