Blood Pressure Measurement Health Article

Definition

Measurement of the pressure exerted by the circulating blood on the walls of the blood vessels, especially the arteries.

Purpose

The purpose of blood pressure measurement is to establish a baseline and detect any abnormalities from the normal state. Measurement is also performed to monitor the effectiveness of medication and other methods used to control hypertension.

Blood pressure should be routinely checked every one to two years. Hypertension often has no symptoms that would make the patient immediately aware that there is a problem and the patient may have had high blood pressure for many years. In most cases there is no known cause for the condition.

Precautions

As there may be no prior knowledge of the patient's previous blood pressure for comparison, it is important that the nurse is aware of the wide range of normal values that apply to patients of different ages. The inflated cuff can cause slight discomfort and this should be taken into account when dealing with very ill patients.

Description

Blood pressure is usually recorded by measuring the force of the blood in the heart where the pressure is greatest, during the contraction of the ventricles as blood is pumped from the heart to the rest of the body (systolic pressure), and during the period when the heart is relaxed between beats and pressure is lower (diastolic pressure).

The flow, resistance, quality, and quantity of blood circulating through the heart, and the condition of the arterial walls are all factors that influence the blood pressure. If blood flow in the arteries is restricted, the reading will be higher.

Hypertension is an elevation in the blood pressure above normal values, with the diastolic pressure being the indicator most commonly used.

Hypotension is a reduction in the blood pressure below normal values.

The blood pressure is taken using a sphygmo- manometer, a hand bulb pump, and a cuff that is the correct size to give a more accurate reading. Children and

adults with smaller or larger than average-sized arms require special sized cuffs appropriate for their needs.

The sphygmomanometer may be electronic or mercury-based. The mercury-based unit has a manually inflatable cuff attached by tubing to the unit that contains mercury and is calibrated in millimeters of mercury. The electronic unit is similar, but is mercury free and inflates and deflates automatically with the reading displayed digitally. Blood pressure can be measured with either unit, although electronic units are becoming more commonplace.

To record blood pressure, the patient should be seated with the left arm bent slightly, the palm facing upwards and the arm bare or with the sleeve loosely rolled up. With an electronic unit, the cuff is placed level with the heart and wrapped around the upper arm, one inch above the elbow. Following the manufacturer's guidelines, the cuff is inflated and then deflated automatically and the nurse records the reading.

If the blood pressure is monitored manually, a cuff is placed level with the heart and wrapped firmly but not too tightly around the arm one inch above the elbow over the brachial artery, with any creases in the cuff smoothed out. A stethoscope is placed over the brachial artery in front of the elbow, the cuff is then inflated until the artery is occluded and no sound is heard through the stethoscope. The cuff is then inflated a further 10 mm Hg above the last sound heard. The valve in the pump is slowly opened no faster than 5 mm Hg per second to deflate the pressure in the cuff to the point where a tapping sound is heard over the brachial artery. This point is noted as the systolic pressure. The sounds continue as the pressure in the cuff is released and the artery is no longer occluded. At this point, the noises are no longer heard and this is noted as the diastolic pressure.

With children, the tapping noise changes to a soft muffled sound. That point is noted as the diastolic pressure, as commonly in children, sounds continue to be heard as the cuff deflates to zero.

The results are charted with the systolic pressure first, then by the diastolic pressure in the following manner, xxx/xx (e.g. 120/70).