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Monday, 20 July 2009 15:39 |
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The standard machine for measuring blood pressure is the sphygmomanometer. It consists of a device with an inflatable cuff, and a glass column containing mercury which measures pressure.
Blood pressure test is easy and painless. The test is done in the hospital, at a doctor’s room or at a private clinic. It can be performed by a nurse or a doctor.
The cuff is applied around the arm and inflated until blood flow is cut off. As the cuff is gradually deflated, a stethoscope is used to listen for sounds caused as blood begin to flows through the arteries again.
The sounds are matched against the levels of mercury in the culm to give the blood pressure reading. Automatic electronic measuring devices do the same thing. They are easier to use, and can be used for home blood pressure monitoring.
What the numbers mean?
Blood pressure is caused by the heart pumping blood through the arteries. At the moment of the heart's most forceful contraction, the pressure in the arteries (in a normal person) is between about 120 mm Hg. This is called the systolic blood pressure.
When the heart relaxes, the pressure in the arteries falls to a low of between about 80 mm Hg. This is called the diastolic pressure.
So the blood pressure is given as a set of two readings; the systolic and the diastolic.
The unit of measurement, in millimetres of mercury or mm Hg for short, is the pressure needed to push the column of mercury up one millimetre in the sphygmomanometer.
The National Heart Foundation Australia recommends the following levels as a guide only.
Normal blood pressure: less than 120/80
High to normal: 120/80 – 140/90
High Blood pressure: equal to or higher than 140/90
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Hypertension Overview 
