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Blood Preasure Basics

Background On The Numbers We Hear Frequently

We all have to have it, whether it's good or not. A blood pressure is necessary to live. It's the force that circulates blood throughout the body. And this essential movement of life-sustaining fluid is necessary to deliver oxygen and other nutrients to the vital organs.

What exactly is blood pressure? It's the measurement of the tension within the arteries. This essential tension is the result of two forces – the pumping of blood from the heart and the resistance of the arteries to the blood that is being pumped from the heart.

To maintain a healthy blood pressure, the arteries must be strong and flexible. This allows the arteries to stretch when the heart beats and pumps blood into them, reducing the amount of pressure needed to push blood throughout the system. In return, this need for less pressure eases the workload on the heart. This leads to a lower heart rate (beats per minute) and a healthier heart.

When your blood pressure is checked, the pressure of the cuff actually closes the arteries in your upper arm for a short period of time.

Measurement Meaning

Relax - If You Can

You've seen the numbers, written like a fraction. Hopefully, they were less than 140/90, which is considered a high-normal reading. But what exactly do the blood pressure numbers mean?

The measurement refers to how high the pressure in the arteries can raise a column of mercury. The numbers actually represent mm HG - millimeters of mercury. The top number is called the systolic pressure and the bottom number is called the diastolic pressure.

  • Systolic – the higher number that measures the pressure within the arteries when the heart contracts (beats) and pushes blood into the circulatory system.
  • Diastolic – the lower number that measures the pressure within the arteries when the heart is resting between beats and is filling with blood.

It's important that blood pressure measurements are taken when a person is at rest. That's because every movement or change of position can have an effect on the result. For this reason, a health professional may take several readings over a period of time to verify the measurement, especially if it's on the high side. About 35% of those with high blood pressure on a single reading will not have an elevated reading if another measurement is taken.

Sometimes having a person other than the doctor measure the blood pressure can provide a more accurate "at rest" reading. That's because some patients get nervous around doctors, the tension raising their blood pressure. Called "white-coat" hypertension, this affects 20% of the population.

Note: The optimal blood pressure reading in regard to cardiovascular risk is 120/80 mm HG.

(Sources: Mayo Clinic Heart Book, American Heart Association.)