Mis à jour : 3 août 2020
Blood pressure is a measure of the force the heart uses to pump blood around the body.
Because blood is a liquid and to all practical considerations in-compressible, blood pressure can be measured at numerous places but best done close to the heart, as pressure is lost as the blood enters smaller and smaller vessels. Most commonly it is measured using the brachial artery in the upper arm but it can also be measured around the thigh.
An external blood pressure device, used correctly, is almost as accurate as invasive arterial monitoring devices.
The measurement is made traditionally using millimeters of mercury (mmHg), because traditional sphygmomanometers used mercury to measure blood pressure owing to its stability at room temperature and has a high density, meaning that it will expand less due as pressure changes. It’s about 14 times denser than water so it’s more practical as well - to get the same effect using water a traditional sphygmomanometers would have to be 14 times larger!
Each heart beat leads to a corresponding pressure increase in the arteries.
The blood pressure reading consists of four important values.
· Systolic: This is the higher number - a reflection, principally, of the pressure during systole (contraction phase) of the heart on the blood within the arteries and the force of this on the arterial wall.
· Diastolic: This is the lower number - a reflection of the pressure maintained in the arteries by the volume of blood alone, without the pressure from the contraction of the heart (during the resting phase of the cardiac cycle)
· I’ll leave mean arterial pressure and pulse pressure out of this answer.
Blood pressure is a dynamic entity. It varies widely depending on what state your body is in. If you are lying down, asleep it is generally lower than if you are up and active. Stress and other psychological states have also been shown to affect it.
Blood pressure important?
A. Blood pressure is important because the higher your blood pressure is, the higher your risk of health problems in the future.
If your blood pressure is high, it is putting extra strain on your arteries and on your heart. Over time, this strain can cause the arteries to become to become thicker and less flexible, or to become weaker.
If your arteries become thicker and less flexible, they will become narrower, making them more likely to become clogged up. If an artery becomes completely clogged up (known as a clot), this can lead to a heart attack, a stroke, kidney disease or dementia.
Few terminologies using in blood pressure.
High blood pressure or essential hypertension is blood pressure in the brachial artery (the artery in the upper arm) equal to or greater than 140/90 mm Hg after a period of rest preferably in the sitting position without prior smoking. All these criteria are apparently too many to handle. However, they are important as large clinical trials and recommendations based upon them are based on these parameters.
Low blood pressure (hypotension) in itself is not a disease. If it is associated with a high pulse rate, cold clammy extremities, low urine output then it is called peripheral circulatory failure or more popularly known as shock. This is a dreaded manifestation of disease and needs urgent intervention without which the person may die. Shock is rarely found outside hospital settings. More common is postural hypotension which in turn may be a manifestation of anti-hypertensive, aging, autonomic neuropathy (a disease of peripheral nerves), or other disease conditions. This basically means that blood pressure falls when the person sits or stands up making her dizzy. Even commoner is a low normal blood pressure, which laymen usually call low blood pressure. People who have blood pressure on the lower side of the normal distribution curve of the population often are "diagnosed" as having "low blood pressure".
Is Low Blood Pressure Harmful?
Appropriately, this should be called low normal blood pressure, which is nothing but a variant of normal blood pressure. There is no reason or evidence that this is harmful. Neither does this require any treatment. In the treatment of hypertension, however, guidelines may vary on recommending the target blood pressure, or how much the blood pressure should be lowered. Some guidelines prefer intensive treatment and some do not. A word of caution here: this has nothing to do with the population that have a low normal blood pressure.
Most of the time low blood pressure is perfectly normal and is certainly not more harmful than high blood pressure.
According to the American Heart Association, doctors really only consider low blood pressure to be dangerous if it causes symptoms such as dizziness, fainting, dehydration, or shallow breathing.
Low blood pressure treatment – low blood pressure is very common now days even in youngster too. Low blood pressure is not as bad as high blood pressure but in some condition low blood pressure cause many diseases. A young healthy person blood pressure is 120/80mmhg. If your blood is lower than this your blood pressure is low and your blood pressure is higher than 120/80 your blood pressure is high. in some people 110/70 also read as normal.
Causes of low blood pressure
1. When thyroid gland not working properly.
Low blood pressure Symptoms?
If you blood pressure is low then you this the symptoms which you feel headache, laziness, sweating, increase in your heart rate or dizziness
What do the numbers mean?
Every blood pressure reading consists of two numbers or levels. They are shown as one number on top of the other.
The first (or top) number is your systolic blood pressure. It is the highest level your blood pressure reaches when your heart beats.
The second (or bottom) number is your diastolic blood pressure. It is the lowest level your blood pressure reaches as your heart relaxes between beats.
Keep your blood pressure low
Even if you do not have high blood pressure at the moment, it is important to keep your blood pressure as low as you can. The higher your blood pressure, the higher your risk of health problems.
For example, a blood pressure of 135 over 85 may be “normal” but someone with this reading is twice as likely to have a heart attack or stroke as someone with a reading of 115 over 75.
High Blood pressure causes
1. Cholesterol gets deposited on arterial walls, causing narrowing of arteries and reducing available space for blood flow thereby increasing pressure on arterial walls. 2. Hardening of arteries. Cholesterol deposition and ageing process causes hardening of arteries, known as atherosclerosis. Arteries loose its natural elasticity resulting in high BP. 3. Water retention. It's caused by some medical conditions like kidney problems etc. Commonest cause of water retention is access salt and alcohol intake. In both the conditions blood volume increases which in turn raises blood pressure. 4. Constriction of arteries. It's caused mainly due to stress, smoking or intake of nicotine. When arteries are constricted blood pressure increases. When one takes medicine it gives relief of symptoms by relaxing arteries or by reducing heart rate or its force but does not eliminate underlying causes discussed above and one gets feeling of cured and continues with unchanged life style, harboring disease in perpetuity.
· High blood pressure is also known by the name of hypertension. Due to our lifestyles that we lead and the kind of food we eat hypertension is growing at an alarming rate. Let us first understand the meaning of blood pressure. In our body, the blood circulates and exerts a pressure on the veins, heart chambers and the walls of arteries. If the force increases it results in high blood pressure. It also causes heart attack and the strokes as it starts the formation of plaque in the arteries. It is very necessary to control the high blood pressure otherwise it may lead to a heart attack.
· It is a silent disease as it is not necessary that it will show the symptoms all the time. The first or upper number reading in blood pressure is known as systolic pressure. The second or lower number in the blood pressure is known as diastolic pressure. It is known to everyone that normal blood pressure is 120/80 mmHg. In hypertension or high blood pressure the systolic pressure increase more than 160 or the diastolic pressure comes to even more than 100.