Dec 16, 2009
Measurement of the pressure exerted by the circulating blood on the walls of the blood vessels, especially the arteries.
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.
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.
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).
Medical staff should explain the procedure fully to the patient and reassure them that recording their blood
pressure is part of normal health checks and that it is necessary to ensure their health is being correctly monitored. The appropriate sized cuff should be used for the patient to give an accurate reading.
The test can be performed at any time but is best performed when the patient has been resting for at least five minutes so that any exertion, such as climbing stairs prior to the test, will not unduly influence the outcome of the reading.
Devices should be checked and calibrated annually by a qualified technician to ensure accurate readings.
Make the patient comfortable. The medical staff should be notified if the blood pressure measurement is above or below normal values. Repeated measurements are required for screening purposes. One elevated reading does not mean that hypertension is present.
Certain physical or psychological conditions can affect a blood pressure measurement by elevating or lowering the reading. These include the following factors:
There is a nationwide initiative to ban the sale of mercury thermometers and mercury devices for monitor ing blood pressure. Health activists are concerned about mercury contaminating the environment after disposal of this equipment. Several states have banned the use of products containing mercury and stores such as Wal-Mart, CVS, and Kmart have already stopped selling mercury thermometers. According to a study by the Mayo Clinic in March 2001, mercury-free devices can monitor information without compromising accuracy. The Environmental Protection Agency (EPA) "Reducing Mercury Use in Health Care" in October 1999 advises using alternative devices to avoid the need for increased regulations in years to come and to protect human health and wildlife by reducing unnecessary exposure to mercury.
The normal values for blood pressure measurement is a systolic pressure of 120 mm Hg and a diastolic pressure of 70-80 mm Hg.
Mild hypertension is a diastolic pressure above 90 mm Hg.
The American Heart Association states that a systolic pressure above 130-139 mm Hg needs to be watched carefully.
Significant hypertension is a systolic pressure above 200 mm Hg.
The blood pressure measurement is recorded and compared with normal ranges for the patient's age and medical condition. Based on the results a decision is made as to whether any further action is required.
Hypertension increases the risk of serious diseases such as heart attack and stroke.
Older children and parents may ask questions about specific concerns they have regarding their blood pressure measurement or a particular disease. The nurse can provide counseling on the normal values of blood pressure, the prevention of illness and injuries, or suggest visiting the patient's doctor who can advise on additional methods to help maintain a healthy blood pressure.
Blood pressure—The pressure of the blood in the arteries measured in millimeters of mercury by a sphygmomanometer or by an electronic device.
Diastolic—Minimum arterial blood pressure during ventricular rest.
Hypertension—High blood pressure.
Hypotension—Low blood pressure.
Pre-eclampsia—A toxic disease occurring in preg- nancy with symptoms including hypertension.
Systolic—Maximum arterial blood pressure during ventricular contraction.
Nagel, Rob. "Measuring Blood Pressure." In Body by Design: From the Digestive System to the Skeleton, edited by Betz Des Chesnes. Farmington Hills, MI: UXL, 2000.
American College of Nurse Practitioners, 503 Capitol Ct. NE #300, Washington, DC 20002. 202-546-4825. E-mail acnp@nurse.org.
American Heart Association. Blood Pressure. AHA National Center, 7272 Greenville Avenue, Dallas, TX 752311. 800-AHA-USA1, A-Z Guide.
American Heart Association. Blood Pressure Testing and Measurement. AHA National Center, 7272 Greenville Avenue, Dallas, TX 752311. 800-AHA-USA1, A-Z Guide.
Blood Pressure. National Library of Medicine. Medical Encyclopedia. <http://www.nlm.nih.gov/medlineplus/ency/article/003398.htm>.
Cooper, Phyllis G. "Blood Pressure." Clinical Reference Systems. Annual 2000, p. 173.
Margaret A Stockley, RGN
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