User manual

User Manual for Multi-parameter Patient Monitor

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

waveforms may disappear suddenly? ...and 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 is calculated on the basis of cuff pressure oscillatory

waveform

envelope, and

the air release speed and heart rate has little effect on the measurement accuracy.

3. Statistics show that, when measuring the hypertension, the measure taken by the oscillating method is

likely to be lower than that taken by the Korotkoff Sound Method. When measuring the hypotension, the

measure taken by the oscillating method is likely to be higher than that by the Korotkoff Sound Method.

But, it doesn’t mean the advantages or disadvantages between the oscillating method and the Korotkoff

Sound Method. Comparison with the results taken by more accurate method, let’s say comparison of the

invasive pressure result with the output value by the blood pressure measuring simulator, will show which

method has more accurate results. In addition, higher or lower value should be a statistical concept. It is

recommended those used to adopt the Korotkoff Sound Method use different physiological calibration for

values determined by the oscillating method.