BP measurement

Working group national high blood pressure education program (1996)

The following are the recommendations by this committee on BP measurement:

1.       Position-sitting

2.       Cuff width-approximately 40% of arm circumference

3.       Diastolic pressure-K5 for both child and adult

4.       Number of measurements-average of 2 or more

Small cuff increases both systolic and diastolic BP.

Non compressible arteries (Monckeberg sclerosis) will produce pseudohypertension.

American heart association updates recommendations for blood pressure measuremens:-

·         Systolic and diastolic blood pressures, as opposed to pulse pressure, remain the best means to classify hypertension. Cardiovascular risk begins to increase steadily as blood pressure rises from 115/75 mm Hg to higher values.

·         15% to 20% of patients with stage I hypertension have elevated blood pressure only in the presence of a physician. This "white-coat" hypertension  is more common in older men and women, and antihypertensive treatment in these patients may reduce office blood pressure white not affecting ambulatory blood pressure.

·          Patients who are older or have a long history of diabetes may have noncompressible brachial arteries , producing pseudohypertension.

·         Orthostatic  hypotension is defined by a decrease  in systolic blood pressure of 20mm Hg or more or diastolic blood pressure of 10mm Hg or more after 3 minutes of quite standing after being supine. Food ingestion, time of day, age, and hydration can impact this form of hypotension, as can a history of Parkinsonism, diabetes, or multiple myeloma.

·         Korotkoff sounds should be used to measure blood pressure. Compared with intra-arterial blood pressure, these sounds generally produce reduced systolic blood pressure values and higher diastolic values.

·         Mercury sphygmomanometers are considered a gold standard for blood pressure measurement, but they are being supplanted by aneroid sphygmomanometers.

·         Oscillometric blood pressure, in which the mean intra-arterial pressure is measured by the point of maximum of oscillation of the sphygmomanometer needle, affords the advantage of more accurate readings in noisy environments. However, this method is inappropriate for patients with noncompressible arteries.

·         Posture:-Before performing a blood pressure reading, the patient should be comfortably seated with the back and arm supported, the legs uncrossed, and the upper arm at the level of the right atrium.  

·         Proper cuff size selection is critical to accurate measurements. The bladder length and width of the cuff should be 80% and 40%, respectively , of the arm circumference. Blood pressure measurement errors are generally worse in cuffs that are too small vs those that are too big.

·         Blood pressure measurement in the sitting and recumbent positions is acceptable. The diastolic blood pressure can be expected to  be about 5mm Hg higher in the sitting position.

·         A different in blood pressure between the two arms can be expected in about 20% of patients. The higher value should be expected in about 20% of patients. The higher value should be the one used in treatment decisions.

·         When measuring blood pressure, the cuff should be inflated to 30mm Hg above the point at which the radial disappears. The sphygmomanometer pressure should then be reduced at 2 to 3 mm/second. Two readings should be performed at least one minute apart.

·         Blood pressure readings in the emergency department do not accurately predict hypertension on subsequent clinic visits.

·         Blood pressure machines stationed in public places are frequently inaccurate.

·         Five of 24 self-monitoring blood pressure systems have been shown to provide consistent, accurate results. Home blood pressure should be at least lower than 137/85 mm Hg. Night time home blood pressure is usually lower than daytime pressure.