Blood pressure is measured in millimetres of mercury (mmHg) corresponding to the height of a column of mercury that could be supported in a mercury sphygmomanometer, a device which until recently was the standard method of measuring blood pressure. Blood pressure is now frequently measured using accurate electronic devices calibrated in mmHg as the standard unit for blood pressure measurement.
Office blood pressure
The most accurate method for measuring blood pressure in the office is to listen for Korotkoff sounds in the brachial artery as cuff pressure is reduced [1].
24-hour ambulatory blood pressure monitoring (ABPM)
Blood pressure can also be assessed by the patient at home. This avoids the potential for white-coat hypertension, a phenomenon described as the increase of a patient's blood pressure in the presence of a physician and makes the measure of early morning blood pressure more feasible.
The best technique for measuring blood pressure is to use an ambulatory monitor, which is typi-cally a small, fully automatic device which can be worn on a belt around the waist. ABPM allows blood pressure to be measured several times an hour over a 24-hours period, and provides an assessment of the patient's circadian rhythm.
Procedure
Hypertension diagnosis should not only be based on repeated blood pressure measurement, but also on other diagnostic measurements, such as:
- evaluation of the patient's family and clinical history
- assessment of associated diseases, such as renal parenchymal disease, renovascular hypertension or drug induced hypertension, also known as secondary hypertension
- search for other risk factors and end-organ damage, for example left ventricle hypertrophy (LVH), arterioscleroses or nephrosis
