Blood pressure
Blood pressure is the force exerted by circulating blood on the walls of blood vessels, crucial for maintaining the flow of blood throughout the body. It is measured in millimeters of mercury (mmHg) using a sphygmomanometer, which records two key readings: systolic pressure (the maximum pressure during heart contraction) and diastolic pressure (the minimum pressure when the heart is at rest). An average blood pressure reading for healthy adults is typically around 120/80 mmHg, while readings of 140/90 mmHg and above indicate hypertension, which can increase the risk of serious health issues such as heart attack and stroke.
Blood pressure can fluctuate based on various factors including age, physical condition, stress, and lifestyle choices like diet and exercise. Maintaining a healthy blood pressure may involve lifestyle changes such as reducing salt and sugar intake, increasing physical activity, and managing stress. In some cases, medications may be necessary to control high blood pressure. Conversely, low blood pressure, or hypotension, may lead to symptoms like light-headedness and fainting, and can be managed through increased fluid and salt intake. Regular monitoring of blood pressure is important for overall health, particularly as one ages or experiences health changes.
Blood pressure
DEFINITION: The force exerted by blood upon the walls of blood vessels as the heart pumps blood through the circulatory system.
Structure and Functions
When the left ventricle of the heart beats, it pumps five liters of blood per minute to the aorta, through the arteries, and into the arterioles. As these blood vessels decrease in diameter, they create resistance to blood flow, and the pressure of the blood against their walls increases. This blood pressure is expressed as two numbers measured in millimeters of mercury (mmHg) by a sphygmomanometer. The first number, called the systolic pressure, is the maximum pressure that occurs when the heart contracts and the ventricle is emptying its blood. The second number, called diastolic pressure, is the minimum pressure that occurs when the heart relaxes, and the ventricle is filling with blood before the next contraction.
Blood pressure depends on the strength of the heart muscle, the volume and thickness of blood being pumped, and the diameter and flexibility of the blood vessels, all of which may vary with age, health, and physical condition. Blood pressure is also affected by activity, diet, hydration, emotional stress, physical pain, tobacco use, weight (including pregnancy), abrupt changes in body position, and medication and drugs (including caffeine and alcohol).
Blood pressure is a commonly measured indicator of the body’s state of health, along with body temperature, pulse rate (number of heartbeats per minute), and respiratory rate (number of breaths per minute). It can be measured noninvasively using a sphygmomanometer, which may be electronic and automatic or require manual inflation and deflation. With the patient seated or lying down, an inflatable cuff is wrapped firmly around the upper arm at the level of the heart with the lower edge of the cuff one inch above the crease in the elbow. The arm should be bare, and any sleeve should be pushed or rolled up without constricting circulation. If the meter is electronic, then the cuff will automatically inflate and deflate when activated, and a digital reading will be displayed. If the meter is manual, then a health-care provider will place the bell of a stethoscope over the large artery on the inside of the elbow, just below the cuff. The cuff is then inflated by quickly squeezing a rubber bulb until the gauge reads ten–thirty mmHg higher than the expected systolic pressure but no higher than 210 mmHg. No sound should be heard through the stethoscope. A valve is opened so that the cuff deflates slowly; the pressure reading should drop two–three mmHg per second. When the sound of pulsing blood is first heard through the stethoscope, the reading on the gauge is the systolic pressure. As the cuff continues to deflate, this sound will disappear, and the reading on the gauge at that point is the diastolic pressure. Blood pressure should be checked at least every year or two. It should be checked more often during illnesses and medical treatments.
Disorders and Diseases
The average blood pressure for healthy adults is 120 over 80 mmHg (written as 120/80). A systolic pressure of 120 to 139 mmHg or a diastolic pressure of 80 to 89 mmHg is considered slightly elevated, a condition called prehypertension. A systolic pressure of at least 140 mmHg or a diastolic pressure of at least 90 mmHg is considered elevated, a condition called hypertension. In some cases, hypertension has no known direct medical cause; however, in other cases, it is secondary to other health conditions, such as kidney disease. Potential risk factors for hypertension include obesity; anxiety, trauma, or pain; poor cardiovascular fitness; obstetric disorders, such as preeclampsia; sickle cell crisis; pancreatitis; medications, such as oral contraceptives, beta-2 agonists, and monoamine oxidase inhibitors; drugs, such as caffeine, cocaine, amphetamines; and withdrawal from alcohol or opiates. Chronic hypertension is a risk factor for heart attack, stroke, and aneurysm.
The goal of hypertension treatment is to get the resting blood pressure below 140/90. In some cases, this may be accomplished solely with lifestyle changes, which should be tried before drug therapy is begun. These lifestyle changes include discontinuing alcohol consumption and tobacco use, reducing dietary salt and sugar intake, eating foods low in saturated fat, performing regular low-intensity exercise, such as walking, and getting sufficient sleep and stress relief. When these changes alone are insufficient, one or more medications may be prescribed, such as diuretics, beta-blockers, calcium-channel blockers, or angiotensin-converting enzyme (ACE) inhibitors. Hypertension is one of the most common health issues, especially as people age.
While hypertension is diagnosed from specific elevated blood pressure measurements, hypotension is diagnosed by symptoms of low blood flow rather than solely by blood pressure numbers. These symptoms include light-headedness, weakness, visual disturbance, and fainting.
To increase the volume and thickness of blood being pumped, patients with hypotension are typically instructed to drink more liquids (excluding caffeinated and alcoholic beverages) and ingest more salt. They must also avoid dehydration from excess sweating and hot showers or baths. To improve the resistance in blood vessels, patients may wear compression stockings and should regularly perform moderate exercise. Little is known about the causes of hypotension, and few medications are available to raise low blood pressure safely.
Perspective and Prospects
Direct measurement of arterial blood pressure was first reported by Reverend Stephen Hales in 1733. He inserted a glass tube in a horse’s artery and found that the column of blood rose to a vertical height of more than eight feet. Pressures were later measured with columns of water and saline, but they still required an unwieldy length of tube. Eventually, a mercury column was used because mercury is more than thirteen times as dense as water, and the column length was more manageable. However, as studies found more evidence of health hazards related to mercury exposure, sphygmomanometers phased out the use of mercury, transitioning instead to aneroid and digital methods.
Bibliography
Alwan, Heba, et al. "Epidemiology of Masked and White-Coat Hypertension: The Family-Based SKIPOGH Study." PLoS One, vol. 9, no. 3, 2014.
Beune, Erik J. A. J., et al. "Culturally Adapted Hypertension Education (CAHE) to Improve Blood Pressure Control and Treatment Adherence in Patients of African Origin with Uncontrolled Hypertension: Cluster-Randomized Trial." PLoS One, vol. 9, no. 3, 2014.
"Blood Pressure." BetterHealth Channel, Victoria State Government, 28 Oct. 2022, www.betterhealth.vic.gov.au/health/conditionsandtreatments/blood-pressure. Accessed 10 Dec. 2024.
“Blood Pressure.” Cleveland Clinic, 7 Jan. 2022, my.clevelandclinic.org/health/diseases/17649-blood-pressure. Accessed 24 July 2023.
"Blood Pressure Medicines." MedlinePlus, National Library of Medicine, 29 Dec. 2023, medlineplus.gov/bloodpressuremedicines.html. Accessed 10 Dec. 2024.
"Blood Pressure Test." NHS, 11 July 2023, www.nhs.uk/conditions/blood-pressure-test/. Accessed 10 Dec. 2024.
Fortmann, Stephen P., and Prudence E. Breitrose. The Blood Pressure Book: How to Get It Down and Keep It Down. 3rd ed. Bull, 2006.
Gatzoulis, Michael A. OCL Pulmonary Arterial Hypertension. Oxford UP, 2011.
Humbert, Marc, et al. Pulmonary Vascular Disorders. Karger, 2012.
Kowalski, Robert E. The Blood Pressure Cure: Eight Weeks to Lower Blood Pressure without Prescription Drugs. Wiley, 2008.
Shibao, Cyndya, et al. "Evaluation and Treatment of Orthostatic Hypotension." Journal of the American Society of Hypertension, vol. 7, no. 4, 2013, pp. 317–24.
SPRINT Research Group. "A Randomized Trial of Intensive versus Standard Blood Pressure Control." New England Journal of Medicine, vol. 373, 2015, pp. 2103–116.
"What Is High Blood Pressure?" Blood Pressure UK, Blood Pressure Association, www.bloodpressureuk.org/your-blood-pressure/understanding-your-blood-pressure/what-is-high-blood-pressure/. Accessed 10 Dec. 2024.
"What Is High Blood Pressure?" National Heart, Lung, and Blood Institute, National Institutes of Health, 25 Apr. 2024, www.nhlbi.nih.gov/health/high-blood-pressure#. Accessed 10 Dec. 2024.