Nibp Monitoring; Measuring Principle - Gima PC-900PRO Mode D'emploi

² The skin placed electrode is unclean or poor contract caused by scurf and hair;
² Electrode long-time used.

8.2 NIBP Monitoring

8.2.1 Measuring Principle

Blood pressure may be measured in an invasive way (whereby the sensor will be inserted into blood vessel directly) or a
non-invasive way. The non-invasive way includes several methodologies, such as the Korotkoff Sound Method and
oscillating method. The Korotkoff Sound Method is used as a conventional way, whereby stethoscope is used to
measure the blood pressure. By the oscillating method, an inflation pump will fill the air, and release it slowly. A
computer will record change of the cuff pressure when the air is released. With this record, the blood pressure value will
be determined. First of all, make sure the signal quality judgment by computer meets the requirements of accurate
calculation (such as sudden limb movement or cuff being hit during the measurement). If the answer is negative, give up
the calculation. If the answer is positive, proceed with calculation of the blood pressure value.
As change of the blood pressure is recorded by electric sensor, which sensitivity is much higher than that of human ears,
the oscillating method uses different definitions for measurement of diastolic pressure, mean arterial pressure and
systolic pressure from the Korotkoff Sound Method. When the oscillating method is used, the circuit in the measuring
apparatus will separate the amplitude of the cuff pressure from its change with pulsation. With the oscillating method,
the blood pressure at the maximum amplitude of cuff pressure is defined as the mean arterial pressure. The blood
pressure at amplitude of cuff pressure forward reduced according to proper proportion is defined as systolic pressure,
while the blood pressure at amplitude of cuff pressure backward reduced according to proper proportion is defined as
diastolic pressure. The maximum change of pulse pressure occurs at these two points. They are equivalent to the point
with pulse sound and the point without pulse sound respectively in the Korotkoff Sound Method.
When the risk of invasive monitoring method outweighs its advantage of accuracy, non-invasive monitoring method
shall be used.
Comparison between blood pressure measuring methods
To overcome the effect of human hearing variation and air release speed on measurement accuracy when the
conventional Korotkoff Sound Method is used to take measure of blood pressure, people have been dedicated to study of
automatic measurement of blood pressure. By now, automatic blood pressure measuring system based on the principle
of oscillating method is mature. In practice, however, various problems are encountered, such as why the measures
taken by the oscillating method is lower or higher than those taken by Korotkoff Sound Method? Why the measures are
inclined to decline? Why, in some cases, no result is obtained in spite of the inflation actions? Why the measure values
have big discreteness and even abnormal data in some cases? Why the SpO
so on. The following explanations are devised to give the answers.
The Oscillating method vs. the Korotkoff Sound Method
Blood pressure measurement by the oscillating method and Korotkoff Sound Method has good correlation with the
invasive measurement. Notwithstanding, any of the non-invasive blood pressure measurements has its one-sidedness
when it is compared to the invasive measurement. The oscillating method has its advantages over the Korotkoff Sound
Method in less error, higher reliability and stability. Their differences may be reflected in the following aspects.
1. The measures by the Korotkoff Sound Method are liable to effect of human factors. For example, different people
may have different sound judging ability, or different reactivity when listening to heart sound and reading mercury
meter. The air release speed and subjectivity may also affect the judgment. By the oscillating method, the
computation is accomplished by the computer, thus relieving the possibility of effect due to human factor.
2. With the Korotkoff Sound Method, the measure is taken on the basis of appearance and disappearance of heart
sound. The air release speed and heart rate may have direct effect on the measurement accuracy. It also has the
disadvantages of rapid air release and poor accuracy. In the contrast, with the oscillating method, the determination
waveforms may disappear suddenly? ...and
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