Blood pressure

A healthcare worker measuring blood pressure using a sphygmomanometer.
A digital sphygmomanometer used for measuring blood pressure
Overview of main complications of persistent high blood pressure
Cardiac systole and diastole
Blood flow velocity waveforms in the central retinal artery (red) and vein (blue), measured by laser Doppler imaging in the eye fundus of a healthy volunteer.
Schematic of pressures in the circulation
A schematic representation of the arterial pressure waveform over one cardiac cycle. The notch in the curve is associated with closing of the aortic valve.
Taking blood pressure with a sphygmomanometer

Pressure of circulating blood against the walls of blood vessels.

- Blood pressure
A healthcare worker measuring blood pressure using a sphygmomanometer.

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An anesthetic machine with integrated systems for monitoring of several vital parameters, including blood pressure and heart rate

Vital signs

Vital signs (also known as vitals) are a group of the four to six most crucial medical signs that indicate the status of the body’s vital (life-sustaining) functions.

Vital signs (also known as vitals) are a group of the four to six most crucial medical signs that indicate the status of the body’s vital (life-sustaining) functions.

An anesthetic machine with integrated systems for monitoring of several vital parameters, including blood pressure and heart rate
Oral glass thermometer
An individual taking their own radial pulse.
Manual sphygmomanometer and stethoscope used to take blood pressure in clinic.

There are four primary vital signs: body temperature, blood pressure, pulse (heart rate), and breathing rate (respiratory rate), often notated as BT, BP, HR, and RR.

Modern stethoscope

Stethoscope

Acoustic medical device for auscultation, or listening to internal sounds of an animal or human body.

Acoustic medical device for auscultation, or listening to internal sounds of an animal or human body.

Modern stethoscope
A girl having her heart listened to with a stethoscope.
This early stethoscope belonged to Laennec. (Science Museum, London)
Early stethoscopes
A Traube-type stethoscope in ivory
Early flexible tube stethoscopes. Golding Bird's instrument is on the left. The instrument on the right is the stethophone.
A doctor using a stethoscope to listen to a patient's abdomen
Parts of a binaural stethoscope
Acoustic stethoscope, with the bell upwards
A Pinard horn used by a U.S. Army Reserve nurse in Uganda
A 3D-printed stethoscope

In combination with a manual sphygmomanometer, it is commonly used when measuring blood pressure.

Heart performance during ventricular diastole: early diastole is a suction mechanism that draws blood 'down' from the left atrium (pink) and right atrium (blue) into each of the two ventricles. Then, in late ventricular diastole, the two atrial chambers begin to contract (atrial systole), forcing additional blood flow into the ventricles.

Diastole

Part of the cardiac cycle during which the heart refills with blood after the emptying is done during systole .

Part of the cardiac cycle during which the heart refills with blood after the emptying is done during systole .

Heart performance during ventricular diastole: early diastole is a suction mechanism that draws blood 'down' from the left atrium (pink) and right atrium (blue) into each of the two ventricles. Then, in late ventricular diastole, the two atrial chambers begin to contract (atrial systole), forcing additional blood flow into the ventricles.
A Wiggers diagram, showing various events during diastole. During early ventricular diastole—see vertical bar marked "Isovolumetric relaxation"—pressure in each ventricle (light-blue trace) begins to drop quickly from the wave height reached during systole. When ventricular pressures fall below those in the atrial chambers the atrioventricular (mitral and tricuspid) valves open, causing blood volume (red trace) in the atria to flow into the ventricles. + In late ventricular diastole, the two atrial chambers begin to contract (atrial systole), causing blood pressure in both atria to increase and forcing additional blood volume into the ventricles. This beginning of the atrial systole is known as the atrial kick—see "Ventricular volume" trace (red) directly above the P-wave in the electrocardiogram trace (dark-blue).

The term is more commonly known as one of the two main components for measuring blood pressure, "diastolic pressure", which is the lowest arterial pressure occurring each heartbeat.

Hypotension

Low blood pressure.

Low blood pressure.

Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood.

Automated arm blood pressure meter showing arterial hypertension (shown by a systolic blood pressure 158 mmHg, diastolic blood pressure 99 mmHg and heart rate of 80 beats per minute)

Hypertension

Automated arm blood pressure meter showing arterial hypertension (shown by a systolic blood pressure 158 mmHg, diastolic blood pressure 99 mmHg and heart rate of 80 beats per minute)
Determinants of mean arterial pressure
Illustration depicting the effects of high blood pressure
Rates of hypertension in adult men in 2014.
Diagram illustrating the main complications of persistent high blood pressure
Image of veins from Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus
Graph showing, prevalence of awareness, treatment and control of hypertension compared between the four studies of NHANES

Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated.

Tetrahydrocannabinol

Orthostatic hypotension

Tetrahydrocannabinol

Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when standing up or sitting down.

Medical student taking blood pressure at the brachial artery

Sphygmomanometer

Medical student taking blood pressure at the brachial artery
Explanation of how blood pressure is measured based on Korotkow sounds
A French sphygmomanometer used during World War I

A sphygmomanometer, a blood pressure monitor, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner, and a mercury or aneroid manometer to measure the pressure.

Venous (darker) and arterial (brighter) blood

Vascular resistance

Resistance that must be overcome to push blood through the circulatory system and create flow.

Resistance that must be overcome to push blood through the circulatory system and create flow.

Venous (darker) and arterial (brighter) blood

Systemic vascular resistance is used in calculations of blood pressure, blood flow, and cardiac function.

MRI video of a teen's heart beating.

Cardiac cycle

Performance of the human heart from the beginning of one heartbeat to the beginning of the next.

Performance of the human heart from the beginning of one heartbeat to the beginning of the next.

MRI video of a teen's heart beating.
The cycle diagram depicts one heartbeat of the continuously repeating cardiac cycle, namely: ventricular diastole followed by ventricular systole, etc.—while coordinating with atrial systole followed by atrial diastole, etc. The cycle also correlates to key electrocardiogram tracings: the T wave (which indicates ventricular diastole); the P wave (atrial systole); and the QRS 'spikes' complex (ventricular systole)—all shown as color purple-in-black segments.
The Cardiac Cycle: Valve Positions, Blood Flow, and ECG
The parts of a QRS complex and adjacent deflections. Re the cardiac cycle, atrial systole begins at the P wave; ventricular systole begins at the Q deflection of the QRS complex.
A Wiggers diagram illustrate events and details of the cardiac cycle with electrographic trace lines, which depict (vertical) changes in a parameter's value as time elapses left-to-right. The ventricular "Diastole", or relaxation, begins with "Isovolumic relaxation", then proceeds through three sub-stages of inflow, namely: "Rapid inflow", "Diastasis", and "Atrial systole". (During the "Diastole" period, the "Ventricular volume" increases (see red-line tracing), beginning after the vertical bar at "Aortic valve closes" and ending with the vertical bar at R in the QRS complex). + The ventricular "Systole", or contraction, begins with "Isovolumic contraction", i.e., with the vertical bar at "A -V valve closes"; it ends with completing the "Ejection" stage at the bar at "Aortic valve closes". During "Ejection" stage, the (red-line) tracing of "Ventricular volume" falls to its least amount (see ejection fraction) as the ventricles pump blood to the pulmonary arteries and to the aorta.
Diastole (at right) normally refers to atria and ventricles at relaxation and expansion together—while refilling with blood returning to the heart. Systole (left) typically refers to ventricular systole, during which the ventricles are pumping (or ejecting) blood out of the heart through the aorta and the pulmonary veins.
CGI animated graphic of the human heart, sectioned, with motions and timing synced with the Wiggers diagram. The section shows: 1) the opened ventricles contracting once per heartbeat—that is, once per each cardiac cycle; 2) the (partly obscured) mitral valve of the left heart; 3) the tricuspid and pulmonary valves of the right heart—note these paired valves open and close oppositely. + (The aortic valve of the left heart is located below the pulmonary valve, and is completely obscured.) The (unsectioned) atria are seen above the ventricles.
Cardiac diastole: Both AV valves (tricuspid in the right heart (light-blue), mitral in the left heart (pink)) are open to enable blood to flow directly into both left and right ventricles, where it is collected for the next contraction.
Cardiac (ventricular) systole: Both AV valves (tricuspid in the right heart (light-blue), mitral in the left heart (pink)) are closed by back-pressure as the ventricles are contracted and their blood volumes are ejected through the newly-opened pulmonary valve (dark-blue arrow) and aortic valve (dark-red arrow) into the pulmonary trunk and aorta respectively.

Throughout the cardiac cycle, blood pressure increases and decreases.

Pressure as exerted by particle collisions inside a closed container

Pressure

Force applied perpendicular to the surface of an object per unit area over which that force is distributed.

Force applied perpendicular to the surface of an object per unit area over which that force is distributed.

Pressure as exerted by particle collisions inside a closed container
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Mercury column
The effects of an external pressure of 700 bar on an aluminum cylinder with 5 mm wall thickness
Water escapes at high speed from a damaged hydrant that contains water at high pressure
Low-pressure chamber in Bundesleistungszentrum Kienbaum, Germany

Blood pressure is measured in millimetres of mercury in most of the world, and lung pressures in centimetres of water are still common.