Omron HEM-9000AI, Инструкция по эксплуатации

Страница: 14 / 96

14
7.Introduction to the HEM-9000AI
7. Introduction to the HEM-9000AI
Functional Description
The OMRON Non-Invasive Blood Pressure Monitor with AI, HEM-9000AI, has been
developed for blood pressure measurement and AI calculations.
Blood pressure measurement is obtained via digital oscillometric method using a blood pressure cuff. An
accompanying AI calculation is made based on several components of the patient's pulse wave, which is
obtained through applanation tonometry (measures pressure required to indent the artery) using a sensor
placed against the radial artery.
Configuration of Pulse Waves
A pulse wave is a wave in a blood vessel generated when blood is pressurized into the aorta by the
contraction of the heart. The pressure changes within the blood vessels create the wave action, and this is
called a pressure pulse wave. Looking closely at the wave, it consists of two primary elements: ejected wave
and reflected wave.
(Refer to Figure 1)
The ejected wave is generated by the contraction of the heart, which sends blood throughout the body. The
reflected wave is generated by the reflection of the ejected wave, after the ejected wave propagates
throughout the body, reflecting from an artery bifurcation or from a peripheral artery.
The pattern formed by the superimposition of these two wave elements is regarded as the pulse wave
pattern.
In addition, an incisura (notch) on the back of the reflected wave represents a pressure change caused by
reverse flow as the aortic valve, located at the opening of the aorta, is closed.
Pulse Wave and Blood Pressure
The pulse wave represents a local blood pressure change caused by the passage of blood from the left
ventricle into the aorta, accompanied by the wave action through the artery. Systolic blood pressure is
measured during the period of ventricular contraction, creating a wave. Diastolic blood pressure is measured
between periods of ventricular contraction.
AI is defined as
AI defines an amplitude value ratio of the peak point (P2) at which the reflected wave is overlapped to the
peak point (P1) at which the ejected wave is overlapped. (Refer to Figure 2)
What AI indicates
When a peripheral blood vessel is stiff, the reflected wave becomes larger. When the blood vessels in the
pulse wave propagation path are stiff, the time in which the reflected wave returns becomes shorter. As a
result, the peak of the reflected wave will be near the peak of the ejected wave. Both of these phenomena
increase AI. The heart enhances myocardial contractility to overcome the increased blood pressure. If this
lasts for a long time, the heart will become strained, showing that when the AI is higher, the “load on the
heart” is higher.
Ejected wave
incisura
Ejected wave
Reflected wave
Reflected wave
The pulse wave is represented
by a combination of the "ejected"
and the "reflected" wave.
[Figure 1] [Figure 2]
P1 P2