Blood pressure

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Blood pressure ( BP ) is the pressure of blood circulation on blood vessel walls. Used without further specification, "blood pressure" usually refers to pressure in the large arteries of the systemic circulation. Blood pressure is usually expressed in systolic pressure (maximum for one heartbeat) during diastolic pressure (at least between two heartbeats) and measured in millimeters of mercury (mmHg), above atmospheric pressure around it (considered zero for comfort).

Blood pressure is one of the vital signs, along with respiratory rate, heart rate, oxygen saturation, and body temperature. Normal resting blood pressure in adults is about 120 millimeters of mercury (16 kPa) of systolic, and 80 millimeters of mercury (11 kPa) diastolic, abbreviated "120/80 mmHg".

Traditionally, blood pressure was measured non-invasively using a mercury-tube sphygmomanometer, which is still generally considered the gold standard of accuracy. Recently other semi-automatic methods have become common, largely due to concerns about potential mercury poisoning, although cost and ease of use have also affected this trend. The initial alternative to sphygmomanometers of mercury tubes is often inaccurate, but modern-validated devices have the same accuracy as mercury devices.

Blood pressure is affected by cardiac output, total peripheral resistance and arterial stiffness and varies depending on the situation, emotional state, activity, and state of health/relative disease. In the short term, blood pressure is regulated by baroreceptors that act through the brain to affect the nervous and endocrine systems.

Low blood pressure due to the state of the disease is called hypotension, and the consistently high pressure is hypertension. Both have many causes. and possibly a sudden attack or long duration. Long-term hypertension is a risk factor for many diseases, including heart disease, stroke, and kidney failure. Long-term hypertension is more common than long-term hypotension and is often undetectable due to rare monitoring and no symptoms.

Video Blood pressure

Classification

Systemic arterial pressure

The risk of cardiovascular disease increases progressively above 115/75 mmHg. In practice, blood pressure is considered too low only if there are visible symptoms.

Observational studies have shown that people who maintain arterial pressure at the lower end of this pressure range have a much better long-term cardiovascular health. There is ongoing medical debate about what the optimal level of blood pressure to target when using drugs to lower blood pressure with hypertension, especially in the elderly.

This table shows the blood pressure classification adopted by the American Heart Association for adults over 18 years of age. This assumes the values ​​are the result of the average resting blood pressure reading measured at two or more visits to the physician.

In November 2017, the American Heart Association announced a revised definition for the category of blood pressure that increases the number of people considered to have high blood pressure.

In the UK, clinical blood pressure is usually categorized into three groups; low (90/60 or lower), normal (between 90/60 and 139/89), and high (140/90 or higher).

Blood pressure fluctuates from minute to minute and usually shows a circadian rhythm over a 24-hour period, with the highest reading in the morning and evening and the lowest reading at night. The loss of normal blood pressure at night is associated with a greater risk of cardiovascular disease in the future and there is evidence that nighttime blood pressure is a stronger predictor of cardiovascular events than daytime blood pressure. Also, a person's blood pressure varies with exercise, emotional reactions, sleep, digestion and time of day (circadian rhythm).

Various other factors, such as age and sex, also affect a person's blood pressure. In children, the normal range is lower than adults and depends on the height. Blood pressure value references have been developed for children in different countries, based on the distribution of blood pressure in children in these countries. As adults get older, systolic pressure tends to increase and diastolic pressure tends to decrease. As a result, in older people, systolic blood pressure often exceeds the normal range of adults, this is thought to be due to increased arterial stiffness.

The difference between left and right arm blood pressure measurements tends to be small. However, there are sometimes consistent differences greater than 10 mmHg which may require further investigation, e.g. for obstructive arterial disease.

Average arterial pressure

Tekanan arteri rata-rata (MAP) adalah rata-rata di atas siklus jantung dan ditentukan oleh output jantung (CO, resistensi pembuluh darah sistemik (SVR), dan tekanan vena sentral (CVP):

${\ displaystyle \! {\ text {MAP}} = ({\ text {CO}} \ cdot {\ text {SVR}}) {\ text {CVP} }}  ÂÂ$

Dalam prakteknya kontribusi CVP (yang kecil) umumnya diabaikan dan begitu

${\ displaystyle \! {\ text {MAP}} = {\ teks {CO}} \ cdot {\ text {SVR}}}  ÂÂ$

MAP dapat diperkirakan dari pengukuran tekanan sistolik ${\ displaystyle \! P _ {\ text {sys}}}  ÂÂ$ dan tekanan diastolik ${\ displaystyle \! P _ {\ text {dias}}}  ÂÂ$ Â

${\ displaystyle \! {\ text {MAP}} \ approxeq P _ {\ text {dias}} {\ frac {1} {3}} (P_ {\ text {sys}} - P _ {\ text {dias}})}  ÂÂ$

Tekanan pulsa

Tekanan nadi adalah perbedaan antara tekanan sistolik dan diastolik yang diukur,

${\ displaystyle \! P _ {\ text {pulse}} = P _ {\ text {sys}} - P _ {\ text {dias}}.}  ÂÂ$

Fluctuations rise and fall arterial pressure results from the pulsatile nature of the cardiac output, ie the heartbeat. The pulse pressure is determined by the interaction of the volume of the heart stroke, the adherence (ability to expand) the arterial system - largely due to the aorta and the large elastic artery - and the resistance flowing in the arterial tree. As it extends under pressure, the aorta absorbs some of the power of the blood spike from the heart during the heartbeat. In this way, the pulse pressure is reduced from what would happen if the aorta did not obey. The loss of arterial adherence that occurs with aging explains the increased pulse pressure found in elderly patients.

Systemic venous pressure

Blood pressure generally refers to arterial pressure in the systemic circulation. However, pressure measurements in the venous and pulmonary system play an important role in intensive care but require the measurement of invasive pressure using a catheter.

Venous pressure is vascular pressure in the veins or in the atrium of the heart. This is much less than arterial pressure, with general values ​​of 5 mmHg in the right atrium and 8 mmHg in the left atrium.

Variants of venous pressure include:

• Central venous pressure, which is a good approximation of right atrial pressure, is the primary determinant of right ventricular end diastolic volume. (However, there are exceptions in some cases.)
• Jugular venous pressure (JVP) is the pressure observed indirectly on the venous system. It can be useful in differentiating different forms of heart and lung disease.
• Porta venous pressure is the blood pressure in the portal vein. Usually 5-10 mmHg

Pulmonary Pressure

Usually, the pressure in the pulmonary artery is about 15 mmHg at rest.

Increased blood pressure in the lung capillaries causes pulmonary hypertension, causing interstitial edema if the pressure rises to above 20 mmHg, and to pulmonary edema at pressures above 25 mmHg.

Maps Blood pressure

Disorders

Blood pressure control disorders include high blood pressure, low blood pressure, and blood pressure that indicate excessive or maladaptive fluctuations.

High

Arterial hypertension may be an indicator of other problems and may have long-term adverse effects. Sometimes it can be an acute problem, such as hypertensive emergency.

Arterial pressure levels put mechanical pressure on artery walls. Higher pressure increases the workload of the heart and the development of unhealthy tissue growth (atheroma) that develops inside the artery walls. The higher the pressure, the more stress is present and the more the atheroma tends to develop and the heart muscle tends to thicken, enlarge and become weak over time.

Persistent hypertension is one of the risk factors for stroke, heart attack, heart failure and arterial aneurysm, and is a major cause of chronic renal failure. Even moderate arterial pressure causes short life expectancy. At very high pressures, arterial pressure averages 50% or more above average, one can expect to live no more than a few years unless treated appropriately.

In the past, much attention was paid to diastolic pressures; but it is now known that high systolic pressure and high pulse pressure (numerical differences between systolic and diastolic pressure) are also risk factors. In some cases, it appears that an excessive drop in diastolic pressure may actually increase the risk, possibly because of the increased difference between systolic and diastolic pressure (see article on pulse pressure). If the systolic blood pressure increases (& gt; 140 mmHg) with normal diastolic blood pressure (& lt; 90 mmHg), it is called "isolated systolic hypertension" and can cause health problems.

For those with heart valve regurgitation, the severity change may be associated with changes in diastolic pressure. In a study of people with heart valve regurgitation comparing separate 2-week measurements for each person, there was an increase in the severity of aortic and mitral regurgitation when diastolic blood pressure increased, whereas when diastolic blood pressure decreased, there was a decrease in severity.

Low

Blood pressure is too low known as hypotension. This is a medical problem if it causes signs or symptoms, such as dizziness, fainting, or in extreme cases, shock.

When arterial pressure and blood flow decrease beyond a certain point, brain perfusion becomes critically decreased (ie, insufficient blood supply), causing dizziness, dizziness, weakness or fainting.

Sometimes the arterial pressure decreases significantly when a patient stands up from a sitting. This is known as orthostatic hypotension (postural hypotension); Gravity reduces the rate of return of blood from the blood vessels beneath the heart back to the heart, thus reducing the volume of stroke and cardiac output.

When people are healthy, the blood vessels beneath their heart quickly narrow and the heart rate increases to minimize and compensate for the effects of gravity. This is done involuntarily by the autonomic nervous system. The system usually takes a few seconds to fully adjust and if compensation is too slow or inadequate, the individual will experience a decrease in blood flow to the brain, dizziness and potential power outages. G-loading improvements, such as those routinely experienced by aerobatic pilots or 'interesting Gs' pilots, greatly increase this effect. Repositioning the body horizontally largely eliminates the problem.

Other causes of low arterial pressure include:

• Sepsis
• Bleeding - blood loss
• Toxins include a dose of blood-pressure drug toxicity
• Hormonal disorders, such as Addison's disease
• Eating disorders, especially anorexia nervosa and bulimia

Shock is a complex condition that causes decreased perfusion critical. The usual mechanisms include loss of blood volume, pooling blood in the blood vessels that reduce adequate return to the heart and/or effective pumping of the heart. Low arterial pressure, especially low pulse pressure, is a sign of shock and contribute and reflects decreased perfusion.

If there is a significant difference in pressure from one arm to the other, it may indicate a constriction (eg, due to aortic coarctation, aortic dissection, thrombosis or embolism) of the artery.

Blood pressure fluctuations

Normal blood pressure fluctuations are adaptive and necessary. Pressure fluctuations that are significantly greater than norms are associated with greater white matter hyperintensity, findings consistent with decreased local cerebral blood flow and an increased risk of cerebrovascular disease. In both groups high and low blood pressure, greater fluctuation rates were found to correlate with an increase in cerebrovascular disease compared with those with less variability, suggesting clinical management considerations of blood pressure fluctuations, even among normotensive older adults. Older individuals and those who have received blood pressure medications are more likely to exhibit greater pressure fluctuations.

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Physiology

During each heartbeat, blood pressure varies between maximum (systolic) and minimum (diastolic) pressure. Blood pressure in the circulation is mainly due to the action of the heart pump. The difference in blood pressure means responsible for blood flow from one location to another in the circulation. The average blood flow rate depends on blood pressure and the flow resistance provided by the blood vessels. Means blood pressure decreases because circulating blood moves away from the heart through the arteries and capillaries due to loss of viscous energy. Mean blood pressure decreases throughout the circulation, although most of the fall occurs along small arteries and arterioles. Gravity affects blood pressure through hydrostatic forces (eg standing), and the valves in the blood vessels, breathing, and pumping of skeletal muscle contractions also affect blood pressure in the blood vessels.

Hemodynamics

Most of the influence on blood pressure can be understood in terms of its effect on cardiac output and resistance (determinants of mean arterial pressure).

Some factors are:

• Volume of blood: the greater the volume of blood, the higher the heart's output. There is some association between dietary salt intake and increased blood volume, potentially resulting in higher arterial pressure, although this varies with individuals and is highly dependent on the response of the autonomic nervous system and the renin-angiotensin system.
• Cardiac output: the heart pumping action is ultimately responsible for blood pressure. Increased or decreased cardiac output can cause an increase or decrease in each blood pressure.
• Systemic vascular resistance: the higher the resistance to blood flow, the higher the upstream arterial pressure is necessary to maintain the flow. In simple terms, the resistance is related to the ship's radius by the Hagen-Poiseuille equation (resistance 1/radius ⁴ , so the smaller the radius, the higher the resistance). Other physical factors affecting the resistance include: the length of the vessels (the longer the vessels, the higher the resistance), the viscosity of the blood (the higher the viscosity, the higher the resistance) and the presence of arterial stenosis (narrow stenosis increases resistance to flow However, increase systemic blood pressure, it decreases downstream flow). Substances called vasoconstrictors can reduce the caliber of blood vessels, thereby increasing blood pressure. Vasodilators (such as nitroglycerin) increase the caliber of blood vessels, thereby reducing arterial pressure.

In practice, each individual autonomic nervous system and other blood regulating systems respond and regulate all of these factors so that, although the above problems are important, they rarely act in isolation and the actual arterial pressure response of a given individual can vary widely in the short and long term.

Rule

Arrangement of endogenous arterial pressure is not fully understood, but the following mechanisms regulate arterial pressure has been well characterized:

• Baroreceptor Reflex: Baroreceptors in the high-pressure receptor zone detect changes in arterial pressure. This baroreceptor sends a signal ultimately to the brainstem medulla, particularly to the rostral ventrolateral medulla (RVLM). The medulla, by way of the autonomic nervous system, adjusts the mean arterial pressure by altering both the strength and speed of cardiac contraction, as well as systemic vascular resistance. The most important artery baroreseptor lies in the left and right carotid sinuses and in the aortic arch.
• Renin-angiotensin system (RAS): This system is generally known for long-term arterial pressure adjustment. This system allows the kidneys to compensate for the loss of blood volume or decrease arterial pressure by activating an endogenous vasoconstrictor known as angiotensin II.
• Aldosterone Flow: This steroid hormone is released from the adrenal cortex in response to angiotensin II or high serum potassium levels. Aldosterone stimulates sodium retention and potassium excretion by the kidneys. Since sodium is the main ion that determines the amount of fluid in blood vessels through osmosis, aldosterone will increase fluid retention, and indirectly, arterial pressure.
• Baroreceptors in low-pressure receptor zone (especially in the vena cavae and pulmonary veins, and in the atria) produce feedback by regulating the secretion of antidiuretic hormone (ADH/Vasopressin), renin and aldosterone. The increase in blood volume results in increased cardiac output by the Frank-Starling law of the heart, in turn increases arterial blood pressure.

These different mechanisms are not always independent of each other, as shown by the relationship between RAS and aldosterone release. When blood pressure goes down a lot of physiological cascade begins to restore blood pressure to a more appropriate level.

1. A decrease in blood pressure is detected by decreased blood flow and thus a decrease in Glomerular filtration rate (GFR).
2. The decrease in GFR is felt as a decrease of Na level by the macula densa.
3. The macula densa causes an increase in reabsorption of Na , which causes water to follow through osmosis and leads to an increase in plasma volume. Furthermore, the macula densa releases adenosine which causes constriction of afferent arterioles.
4. At the same time, juxtaglomerular cells feel a decrease in blood pressure and release of renin.
5. Renin alters angiotensinogen (inactive form) to angiotensin I (active form).
6. Angiotensin I flows in the bloodstream until it reaches the lung capillary where angiotensin converting enzyme (ACE) acts on it to convert it to angiotensin II.
7. Angiotensin II is a vasoconstrictor that will increase blood flow to the heart and then preload, eventually increasing the cardiac output.
8. Angiotensin II also causes an increased release of aldosterone from the adrenal gland.
9. Aldosterone further increases Na and H ₂ O reabsorption in the distal tubules of the nephron.

Currently, RAS is pharmacologically targeted by ACE inhibitors and angiotensin II receptor antagonists, also known as angiotensin receptor blockers (ARBs). The aldosterone system is directly targeted by spironolactone, an aldosterone antagonist. Fluid retention can be targeted by diuretics; the antihypertensive effect of diuretics is due to their effect on blood volume. Generally, baroreceptor reflex is not targeted at hypertension because if blocked, the individual may suffer from orthostatic hypotension and fainting.

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Measurement

Arterial pressure is most often measured through a sphygmomanometer, which historically uses the height of the mercury column to reflect the pressure in circulation. The most common automatic blood pressure measurement technique is based on the so-called "oscillometric" method. Blood pressure values ​​are generally reported in millimeters of mercury (mmHg), although aneroids and electronic devices do not contain mercury.

For every heartbeat, blood pressure varies between systolic and diastolic pressure. Systolic pressure is the peak pressure in the arteries, which occurs near the end of the heart cycle when the ventricles contract. Diastolic pressure is the minimum pressure in the arteries, which occurs near the beginning of the heart cycle when the ventricles are filled with blood. Examples of measured normal values ​​for resting and healthy adult humans were 120 mmHg systolic and 80 mmHg diastolic (written 120/80 mmHg, and pronounced as "one-twenty-eighty").

Systolic and diastolic arterial blood pressure is not static but undergoes a natural variation from one heartbeat to another and throughout the day (in circadian rhythms). They also change in response to stress, nutritional factors, medication, illness, exercise, and momentarily from standing. Sometimes the variations are large. Hypertension refers to abnormally high arterial pressure, compared with hypotension, when it is abnormally low. Along with body temperature, respiratory rate, and pulse, blood pressure is one of the four major vital signs routinely monitored by medical professionals and healthcare providers.

Measure the pressure invasively, by penetrating the arterial wall to take measurements, much less frequently and usually limited to hospital settings.

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Fetal blood pressure

In pregnancy, it is the fetal heart and not the heart of the mother that builds the blood pressure of the fetus to move blood through the circulation of the fetus. Blood pressure in the fetal aorta is approximately 30 mmHg at 20 weeks gestation, and increases to about 45 mmHg at 40 weeks gestation.

Average blood pressure for term infants:

• Systolic 65-95 mmHg
• Diastolic 30-60 mmHg

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References

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Further reading

• Pickering TG, Hall JE, Appel LJ, et al. (2005). Professional Public Education Subcommittee of the American Heart Association Council on High Blood Pressure Research. "Recommendations for measuring blood pressure in humans and animal experiments: Part 1: measurement of blood pressure in humans: a statement for professionals from the Professional and Public Education Subcommittee of the American Heart Association Council on High Blood Pressure Research". Hypertension . 45 (5): 142-61. doi: 10.1161/01.HYP.0000150859.47929.8e. PMID 15611362 . Retrieved 2009-10-01 .

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External links

• Association of Blood Pressure (UK)
• About High Blood Pressure, American Heart Association
• Blood Pressure Control, Toronto General Hospital
• Blood Pressure Chart, Vaughn's Summaries

Source of the article : Wikipedia