Parameter Circuit Descriptions
Theory of Operation
1 - 16
0070-10-0591-01
Trio™ Service Manual
1.4.3
NIBP
The monitor measures non-invasive blood pressure using the oscillometric method. Detailed
measurement procedures follows:
1.
Inflate the cuff encircled around the upper arm until the pressure in the cuff blocks the
blood flow in the artery of the upper arm.
2.
Then deflate the cuff according to the requirement of the algorithm.
3.
With the pressure decreasing in the cuff, the arterial blood will palpitate with the pulse,
which results in pulsation in the cuff. Through the pressure sensor, connected to the
bladder of the cuff, a pulsation signal synchronous with the patient's pulse will be
generated.
4.
After being filtered by a high-pass filter (about 1 Hz), this signal becomes the pulsating
signal and is amplified. The amplified signal is then converted into a digital signal by
the A/D converter.
5.
After processing this digital signal, systolic pressure, diastolic pressure and mean
pressure can be obtained. To avoid measurement errors, choose appropriate cuffs for
patient size. The NIBP module also has an overpressure protection circuit to prevent the
cuff from being inflated to a very high pressure.
The main operating modes of NIBP are:
A.
Adult/Pediatric
Select according to the patient size, weight and age.
B.
Manual Measurement
Manual measurement is also called single measurement. It means the monitor only
performs one measurement for each time the
NIBP
key is pressed.
C.
Interval Measurement
Interval measurement means to perform one measurement within selected time cycle.
Time intervals can be set up as:
1
,
2
,
3
,
4
,
5
,
10
,
15
and
30
minutes,
1
,
2
, and
4
hours,
OFF
,
CONT.
(Continuous). If set to continuous, the monitor will perform a
measurement continuously for 5 minutes then revert to an interval setting of 5 min.
Continuous measurement is effective in monitoring changes in blood pressure.
1.4.4
SpO
2
SpO
2
Plethysmograph measurement is employed to determine the oxygen saturation of
hemoglobin in the arterial blood. If, for example, 97% hemoglobin molecules in the red
blood cells of the arterial blood combine with oxygen, then the blood has a SpO
2
oxygen
saturation of 97%. The SpO
2
numeric on the monitor will read 97%. The SpO
2
numeric
shows the percentage of hemoglobin molecules which have combined with oxygen
molecules to form oxyhemoglobin. The SpO
2
/Pleth parameter can also provide a pulse rate
signal and a plethysmograph. Arterial oxygen saturation is measured by a method called
pulse oximetry. It is a continuous, non-invasive, method based on the different absorption
spectra of reduced hemoglobin and oxyhemoglobin. It measures the amount of light that is
transmitted through patient tissue (such as a finger or an ear).
