In young people it varies normally from 100 to 140 mm, and in people at 60 years of age from 140 to about 170 mm. Blood pressure also varies according to the time of day and the kind of activity a person is engaged in. It is usually lowest just before awakening in the morning. Strenuous physical activity can increase the systolic blood pressure 60 to 80 mm above normal. Excitement, nervous tension, or fright raises the systolic blood pressure.
Increased weight tends to lead to increased blood pressure.
Errors in blood pressure measurement can result from failure of the cuff to reach and compress the artery. The cuff diameter should be 20 per cent greater than the diameter of the limb, the bladder of the cuff must be centered over the artery, and the cuff must be wrapped smoothly and snugly to assure proper inflation. When a mercury gauge is used, the meniscus should be at eye level to avoid a false reading. The blood pressure is displayed on an oscilloscope at the bedside so that the patient's pressure can be determined at a glance. This intra-arterial technique of blood pressure monitoring provides accurate, objective, and continuous data on the patient's status.