Blood Pressure

What is measured?

The doctor measures the maximum pressure (systolic) and the lowest pressure (diastolic) made by the beating of the heart.

How is blood pressure measured?

It is important that the patient is relaxed and rested for at least 5-10 minutes before having their blood pressure taken. The blood pressure can be measured in several different ways depending on what the measurement is going to be used for, but this is what normally happens:

What is high blood pressure?

Blood pressure higher than 150/90 (systolic/diastolic) when the individual is resting is considered a high blood pressure reading. Some people, particularly diabetics, should aim for an even lower blood pressure reading of less than 140/85.

Blood pressure fluctuates during the day in any one person. Anxiety, stress or discomfort can temporarily raise the blood pressure of people who do not have significant hypertension (high blood pressure requiring treatment).

For this reason, in all but the most severe cases, it is best not to make judgments about the significance of raised blood pressure until three or four measurements have been taken over some weeks, allowing an estimate of the average blood pressure.

Ambulatory blood pressure monitoring

Ambulatory blood pressure monitoring (ABPM) involves measuring an individual's blood pressure for 24 hours, as they go about their usual daily routine and when they are asleep. Measuring the blood pressure at regular intervals in this way using mobile equipment designed to interfere as little as possible with normal activities, allows the doctor to obtain a graphical picture of blood pressure variation in a normal environment. Average daytime ABPM blood pressure is lower than equivalent clinic blood pressure and so readings above 140/85 for non-diabetics and 140/80 for those individuals with diabetes using ABPM are considered to be high.

Situations in which ABPM may be used include:

Although the average blood pressure reading for adults is 120/80, a slightly higher or lower reading (for either number) may not be a problem. If blood pressure goes above 140/90, however, some form of treatment-diet or drugs-may be needed. Lower blood pressure readings (for example, 110/70) are thought to be safe for most people.

Often in older adults the first number (the upper or systolic number) is high while the second (the lower or diastolic) number is normal. This condition is called isolated systolic hypertension, and it also should be treated. Studies prove that lowering the systolic number cuts down on strokes and heart attacks in people age 60 and over.

What are the numbers in the blood pressure test and what is abnormal? Blood pressure is read out in two numbers like 120 over 80 or 140/90, etc. The top number is called systolic and corresponds to the pressure created in the arteries when the heart contracts and pumps blood into the arteries. The second or bottom number is called diastolic and is the pressure in the arteries when the heart has finished pumping and is waiting to fill with more blood for the next beat.

Abnormal pressures are defined as an average pressure of 140/90 or more in three separate tests taken over several days or weeks. It does not matter if one or both numbers are high although most people with Hypertension have both numbers elevated. Also, the higher the number the more chance and the quicker you will develop the damage described above.

Blood Pressure Levels

Blood pressure is measured in millimetres of mercury (mm Hg). The classifications in the table below are for people who aren't taking antihypertensive (blood pressure-lowering) drugs and aren't acutely ill. When a person's systolic and diastolic pressures fall into different categories, the higher category is used to classify the blood pressure status. Diagnosing high blood pressure is based on the average of two or more readings taken at each of two or more visits after an initial screening.