Blood pressure is a measure of the force exerted on the artery walls. A bad blood pressure can be too high or low. An abnormally low blood pressure, or hypotension, compromises blood delivery to the body tissues. An abnormally elevated blood pressure, or hypertension, damages the blood vessels, with potentially life-threatening consequences.
Identification
A blood pressure measurement includes the systolic and diastolic pressure. The systolic pressure reflects the force exerted on the arteries when the heart contracts. The diastolic pressure is the force in the arteries between heart contractions. Blood pressure measurements are reported as the systolic pressure/diastolic pressure in mmHg, a unit of force.
According to the National Institutes of Health, a normal adult blood pressure is less than 120/80 mmHg. A systolic blood pressure of 120 to 139 mmHg or a diastolic pressure of 80 to 89 mmHg constitutes prehypertension. NIH defines stage 1 hypertension as a systolic pressure of 140 to 159 mmHg or a diastolic pressure of 90 to 99 mmHg. A systolic pressure of 160 mmHg or higher, or a diastolic pressure of 100 mmHg or higher reflects Stage 2 hypertension.
Hypotension is less specifically defined than hypertension because of normal variation in the population. Generally, a blood pressure lower than 90/60 mmHg causes symptoms of hypotension, reports the National Library of Medicine encyclopedia MedlinePlus.
Hypotension Effects
Mild to moderate hypotension commonly causes lightheadedness or dizziness, especially when rising to a standing position. This symptom occurs because the low pressure in the circulatory system leads to inadequate blood flow to the brain. Fainting may occur if the blood pressure drops significantly. Severe hypotension can cause the life-threatening medical condition known as cardiovascular shock. With this condition, the vital organs of the body do not receive sufficient blood flow to maintain normal function. Without emergency treatment, the organs can fail and permanent damage may occur, explains the National Heart Lung and Blood Institute.
Hypertension Effects
Unlike hypotension, which usually causes symptoms, most people with high blood pressure have no symptoms. This condition, however, gradually causes progressive and potentially life-threatening damage to the blood vessels and body organs. Chronic hypertension can damage the heart and kidneys, leading to failure of these organs, reports the National Heart Lung and Blood Institute. Hypertension-induced damage to the eye blood vessels can potentially cause vision loss. Chronically elevated blood pressure can cause ballooning of the blood vessels, or aneurysm formation. An aneurysm rupture can cause a stroke or life-threatening internal bleeding.
Prevention
Lifestyle measures can reduce the risk for developing hypertension. The National Heart Lung and Blood Institute recommends avoiding excessive salt and alcohol intake; not smoking; maintaining a healthy body weight; staying physically active; and managing stress.
Hypotension often occurs with excessive water loss due to illness or profuse sweating. Staying well hydrated may help reduce the risk for temporary episodes of hypotension.
Significance
Approximately one-third of the U.S. population has hypertension, according to the American Heart Association. Hypertension is a significant risk factor for the development of heart disease, the leading cause of death among Americans, according to the Centers for Disease Control and Prevention.
References
- U.S. Department of Health and Human Services, National High Blood Pressure Education Program: The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure
- MedlinePlus: Hypotension
- National Heart Lung and Blood Institute: Hypotension
- National Heart Lung and Blood Institute: High Blood Pressure
- American Heart Association: Heart Disease and Stroke Statistics--2010 Update
