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South Baylo Univ.
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Blood Pressure
Listed : [2001-07-16, 02:50:59]
Nowadays, a manometer is quite useful for those who suffer from high or low blood pressure, or with any blood pressure related diseases. Having some common sense about blood pressure is helpful in order to stay healthy.

1. Basic common sense about blood pressure

What is blood pressure?

The heart provides blood to all parts of the body. Vessel walls build pressure, and this pressure is called “blood pressure”. Blood is propelled by contraction of the left ventricle of the heart. The pressure produced here passes into the main artery and goes to the peripheral vascular system of the body. This pressure is high in the great arteries, and low in the end organs. Blood pressure can be measured in different blood vessels and the measurement of blood pressure in each part is different. Generally, blood pressure is measured from the medium sized blood vessel (artery) that is close to the heart - for instance, the blood vessel of arm. Therefore, blood pressure is inner pressure of the blood vessels.

Maximal Blood Pressure, Minimal Blood Pressure, Pulse Pressure

Blood pressure of the artery becomes maximized by the ventricle's contraction, which is called “maximal blood pressure”. When the heart starts to expand, the blood pressure decreases. If the pressure of the ventricle becomes lower than the pressure of the artery, the arterial valve closes and the outflow of blood from the ventricle ceases. The next contraction starts, and the arterial valve begins to open. The blood pressure just prior to this is the lowest, and is called “minimal blood pressure”. In addition, the difference between maximal blood pressure and minimal blood pressure is called “pulse pressure”. The pulse pressure becomes greater when the amount of blood from the heart increases, the main artery wall hardens, or loses its elasticity.

2. Change of blood pressure

Blood pressure is not always constant, and its rate of change is different depending on the state or condition of the body.

(1) Change during daytime

Even a healthy person's blood pressure changes dramatically during a day. It is the lowest in the morning, highest at noon, goes down a little in the afternoon, and very low while sleeping.

(2) Change due to age

Human blood pressure is proportional to age. Maximal blood pressure of a newborn baby is about 80, and it becomes 100 around the age of six. Around the age of 20, it is 120. It becomes higher in proportion to height. Men have higher blood pressure between the ages of 20 to 40. After the age of 40, women tend to have higher blood pressure. It is different from the change of minimal blood pressure that is due to age. The blood pressure of both men and women is higher between the ages of 30 and 50. However, between the ages of 50 and 60, there isn’t any change, and becomes rather lower in the 70's.

3. Measuring method of blood pressure

Wrap cuffs around the upper arm, and increase pressure by pumping air into it. Water transport manometer and aneroid manometer are usually used. We want to address the method of auscultation here.

* Method of auscultation: Wrap cuffs around the upper arm and apply pressure over the brachial artery. Listen to the sound of blood vessel with a stethoscope. Apply enough pressure to stop the blood flow, and start taking air out little by little. After a while, the sound of blood vessel can be heard (first sound). We consider this as the maximal blood pressure (but needs to be consistent). If you lower the pressure (as the air goes out), the sound of blood pressure becomes loud and dull (second sound). Lowering the pressure more changes the sound (third sound). Lowering even more makes the sound a little noisy (fourth sound), and the sound dies suddenly (fifth sound). Generally, the pressure measured at the fifth sound is considered as the minimal blood pressure.

4. Change of blood pressure depends on the method of measurement

(1) Position of body when measuring: The change of blood pressure is different depending on the position of the body; however, a healthy person will not see much difference. There are three positions of measuring blood pressure, which include lying, sitting, and standing positions. Usually, it is measured in the sitting position. It is important to note the position in which blood pressure was measured for a more accurate result.

(2) Difference between two sides: There is a difference of blood pressure between the right and left arms. The difference is about five to 10, but it is normal. The right arm of a right-handed person is higher than the left one, and the left arm of a left-handed person is higher than the right one.

(3) Thickness of upper arm: If the upper arm is too thick for the cuff, blood pressure is measured higher than actual. However, if the upper arm is thinner than the cuff, blood pressure is measured lower than actual.

(4) Height of measuring point: If the cuff or the measuring instrument is placed lower than the heart, the measurement will not be accurate.

(5) With tight clothes on: Results in a lower measurement.

5. Self-control of blood pressure

Neural Self-Control: The self-control of blood pressure that is developed through the nerve is very strong. It responds quickly to the bodily situation. It reduces or expands the blood vessel, and changes the resistance of blood vessel as well. Furthermore,it accelerates or suppresses the heart's activities, and influences the cardiac output. This controls the blood pressure.

Liquid Control: The hormone that is secreted from the kidney and adrenal cortex controls Blood pressure. Controlling the kidney's blood flow acts as a stimulator, and increases the production of the hormone. This hormone contracts the blood vessel, and maintains high blood pressure.

6. High Blood Pressure and Low Blood Pressure

Individuals have different blood pressures, and it changes frequently. Therefore, it is difficult to set a certain measurement and consider it abnormal. Generally, when the maximal blood pressure is less than 140 mmHg and the minimal blood pressure is less than 90 mmHg, it is considered normal. When the maximal blood pressure is more than 120 mmHg or the minimal blood pressure is more than 95 mmHg, it is considered as high blood pressure.
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