A blood pressure cuff is wrapped around the upper arm. It is inflated to levels higher than the pressure in the artery, temporarily stopping the flow of blood. A stethoscope is placed over the artery beyond the cuff. The pressure in the cuff is gradually decreased. As soon as the pressure in the cuff is lower than that in the artery, the stethoscope picks up the sound of the blood beginning to flow turbulently through the artificially narrowed artery.
Blood pressure varies with normal activities during the day.
It goes up with exercise and goes down with rest and during sleep. This is normal. Some people, however, have readings that are elevated even at rest. It is now recognized that the risk of complications from untreated hypertension rises with the degree and duration of elevation of blood pressure. This understanding has led to guidelines that classify blood pressure readings for adults into different levels.