Blood pressure is a measure of the pressure of the blood against the walls of the arteries. This pressure is a result of the heart pumping blood into the arteries and through the circulatory system and also the force of the arteries resisting the blood flow. According to the National Heart, Lung and Blood Institute, about one in every three adults in the United States has high blood pressure.
Blood Pressure Numbers
Blood pressure readings are measured in millimeters of mercury, or mmHg, and are reported as systolic pressure over diastolic pressure. The systolic number measures the pressure from the heart pumping blood throughout the body. The diastolic number represents the pressure when the heart relaxes between beats, or when the heart is at rest.
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Measuring Blood Pressure
Blood pressure readings are typically obtained with the person in a seated position and the arm slightly bent and resting on a table at the same level as the heart. A blood pressure cuff is then wrapped tightly around the arm, above the elbow. The large artery on the inside of the arm is then located and the head of the stethoscope is placed on it to obtain a pulse. The cuff is inflated until the column of mercury reads at least 30 mmHg higher than the usual systolic pressure, or to about 210 mmHg if usual systolic pressure is unknown. The stethoscope is used to listen for the sound of blood rushing through the artery. Once a pulse can be heard, the cuff pressure is then allowed to fall gradually. The level on the mercury dial at which blood pulsing is first heard is recorded. This is the systolic pressure. As the air continues to be let out, the sounds will disappear. The level on the mercury dial in which sounds are no longer heard through the stethoscope is recorded. This is the diastolic pressure.
Categories for Blood Pressure
According to the National Heart, Lung and Blood Institute, normal blood pressure is when systolic pressure, or the top number, is less than 120 and diastolic pressure, the bottom number, is less than 80. Prehypertentsion is when systolic pressure is between 120 and 139 mmHg or diastolic pressure is between 80 and 89 mmHg. Stage 1 high blood pressure is when systolic pressure is between 140 and 150 mmHg, or diastolic pressure is between 90 and 99 mmHg. Stage 2 hypertension is when systolic pressure is 160 mmHg or higher or diastolic pressure is 100 mmHg or higher.
When to Check Blood Pressure
According to MedlinePlus, the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommends screening adults for high blood pressure every two years if their blood pressure is usually less than 120/80 mmHg. Adults with higher blood pressure readings should have their blood pressures checked more frequently as high blood pressure typically presents no symptoms and can lead to a variety or illnesses or diseases.
Special Considerations
Most doctor's offices will take blood pressure routinely as part of an appointment. Community events may also offer free blood pressure screens. Blood pressure readings taken at home may be more accurate than measurements taken at the doctor's office as nerves may affect blood pressure readings. Repeated measurements are important, as a single high measurement does not indicate a diagnosis of high blood pressure.
