Diagnosis
Most physical exams include a blood pressure measurement. Patients should not smoke or drink caffeinated beverages within 30 minutes before their blood pressure measurement.
The Sphygmomanometer
- The standard instrument used to measure blood pressure is called a mercury sphygmomanometer. Measurements are given as units of mercury, which has filled the central column in standard sphygmomanometers for years. (Some people view the mercury sphygmomanometer as an environmental health hazard, but modern devices are designed to prevent mercury spillage.)
- An inflatable cuff with a meter attached is placed around the patient's arm over the artery while the patient is seated, their back is supported, and the arm being used is around the level of the heart. The inflated cuff briefly interrupts the flow of blood in the artery, which then resumes as the cuff is slowly deflated.
- The person taking the blood pressure listens through a stethoscope for so-called Korotkoff sounds, which first appear as blood begins to flow through the artery as the cuff is deflated and then change in tone and volume.
- The first pumping sound your health care provider hears is recorded as the systolic pressure, and the last sound is the diastolic pressure.
- If a first blood pressure reading is above normal, the health professional may take two or more measurements separated by 2 minutes with the patient sitting or lying down. Another measurement may be taken after the patient has been standing for 2 minutes. If the measurements are still elevated, your health care provider should take blood pressure readings from both arms.
Although this test has been used for more than 90 years, it is not completely accurate or sensitive. The following factors can cause a falsely low pressure reading:
- An arm cuff that is too wide
- Recent exercise
- Not smoking for a while after heavy, long-term smoking
Falsely high pressure can result from:
- An arm cuff that is too small
- Talking during the test
- Recently consuming foods or beverages (such as coffee) that raise blood pressure
Office blood pressure readings taken by a doctor are more likely to be higher than readings measured at home. This so-called white-coat hypertension requires additional readings by a nurse or by the patient. Home monitoring improves the accuracy of a simple office measurement. An average of all the measurements will be considered in the diagnosis of hypertension. If high normal or high blood pressure persists, further tests should be performed to determine if the organs are affected.
Home Monitoring
Monitoring Equipment. A number of methods are available for checking blood pressure between doctor visits. Evaluating blood-pressure outside of the doctor's office is useful for people who experience wide blood pressure swings, such as those who have white-coat hypertension or show poor response to drug therapy. For some patients, accurately measuring blood pressure at home over a full day can be a significantly better predictor of cardiovascular risk than standard office-based measurements.
- Devices are available that allow 24-hour ambulatory blood pressure monitoring and electronically store results for analysis by the doctor. It is not clear if their added benefits justify their expense, however.
- Manual cuffs with a sphygmomanometer and a stethoscope are fairly accurate. The far majority of people can be trained to use these correctly. The cuff must be the right size (one size does not fit all). Devices that use a digital readout and a cuff that can be electronically inflated and deflated are available, but are not always well standardized and may underestimate blood pressure.
Blood Pressure Variations at Home. In general, everyone's blood pressure varies in the same way throughout a given day. In monitoring at home, it is important to note these changes:
- Blood pressure is usually highest at work.
- It drops slightly at home.
- It then normally dips to its lowest level during sleep. There are important exceptions. Certain people have a condition called nondipper hypertension, in which blood pressure does not fall at night. Postmenopausal women appear to be at particular risk for this phenomenon, and it may pose a special danger for heart disease and stroke (particularly in older African-American women). It has also been linked to salt-sensitivity and insulin resistance.
- Upon waking, pressure in most people typically increases suddenly. In people with severe high blood pressure, this is the highest risk period for heart attack and stroke.
Some studies have reported that when patients record and report their own blood pressure, they are unreliable and don't always tell the truth. Despite the difficulties and controversy surrounding this issue, home blood pressure monitoring has been shown to encourage patients to use measures that control their blood pressure and thereby reduce the risk of cardiovascular events.
Physical Examination for Complications of Hypertension
If blood pressure is elevated, the doctor will check the patient's pulse rate, examine the neck for distended veins or an enlarged thyroid gland, check the heart for enlargement and murmurs, and examine the abdomen and the eyes.
Medical History
If hypertension is suspected, the doctor should obtain the following information:
- A family and personal medical history, especially incidence of high blood pressure, stroke, heart problems, kidney disease, or diabetes.
- Risk factors for heart disease and stroke, including tobacco use, salt intake, obesity, physical inactivity, and unhealthy cholesterol levels.
- Any medications being taken.
- Any symptom that might indicate so-called secondary hypertension (that is, caused by another disorder). Such symptoms include headache, heart palpitations, excessive sweating, muscle cramps or weakness, or excessive urination.
- Any emotional or environmental factors that could affect blood pressure.
Laboratory and Other Tests
If a physical examination indicates hypertension, additional tests may help determine whether it is secondary hypertension or essential hypertension (no other disorder is present) and whether organ damage is present.
Blood Tests and Urinalysis. These tests are performed to check for a number of factors, including potassium levels, cholesterol, blood sugar, infection, kidney function, and other possible problems. Measuring blood levels of the protein creatinine, for example, is important for all hypertensive patients in order to determine kidney damage. Patients suspected of having problems involving the adrenal glands may have several tests.
Tests to Evaluate the Heart. These tests include:
- An electrocardiogram (ECG) is performed on most patients in the doctor's office.
- An exercise stress test may be needed for patients who also have symptoms of coronary artery disease.
- An echocardiogram is needed when it would help the doctor decide whether to start treatment. Most of the time this test is not necessary for patients who have only hypertension and no other symptoms.
Tests To Evaluate the Kidneys. These tests include:
- A Doppler or duplex test may be performed to see whether one of the arteries supplying blood to the kidney is narrowed, a condition called renal artery stenosis.
- An ultrasound may also be performed to examine the kidneys.
