What is normal blood pressure?

Arterial hypertension

Hypertension is a chronic disease that affects millions of people around the world. It is estimated that about 20% of the entire population have blood pressure levels above normal. In the elderly, hypertension is even more common, being present in more than half of people.

Hypertension is the most common risk factor for cardiovascular disease and stroke (brain stroke). High blood pressure is also responsible for other serious problems, such as chronic kidney failure, aneurysms, and damage to the blood vessels in the eyes. As if all the possible complications were not enough, hypertension still has another problem: it is a silent disease that does not cause symptoms in most cases.

Therefore, the only way to know if someone is hypertensive is by measuring their blood pressure. But what are normal blood pressure values? In this article we will show you what are the desirable values ​​of blood pressure for teenagers, adults and seniors.

What is blood pressure?

Blood pressure is the pressure the blood exerts on the walls of the arteries. Let’s make an analogy: imagine an all empty and withered hose. As we turn on the water, the pressure inside the hose builds up and its walls stretch. As the hose is an open system, no matter how much we open the faucet, the fact that water comes out of one of the ends prevents the pressure under the wall of the hose from becoming too high.

In the human body, however, the circulatory system is a closed system, if the pressure inside the vessels increases, the blood has nowhere to go, and the only thing the body can do is to stretch the blood vessels in order to hold the circulating blood volume.

Theoretically, blood vessels are self-regulating, that is, they dilate or compress according to the volume of circulating blood, in order to keep blood pressure more or less constant. If the blood volume decreases a little, the vessels constrict (vasoconstriction); if the blood volume increases a little, the vessels dilate (vasodilation). Of course there is a limit, if the blood volume decreases too much or increases too much, no matter how much the arteries constrict or expand, they will not be able to maintain the blood pressure at an adequate level.

Therefore, you can already understand that one of the causes of high blood pressure is an excessive increase in the volume of blood inside the blood vessels. This excess usually occurs when the body retains too much salt and water. However, most hypertensive patients do not have excess fluid in the body, at least not enough to exceed the ability of the vessels to dilate. What happens is a failure in the self-regulation capacity. Arteries are always more compressed than necessary for blood pressure to stay normal.

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The origin of the loss of the ability to self-regulate blood pressure, which gives rise to hypertension, is a complex process and still not well understood. It involves genetic factors, the amount of salt (sodium) in the body, the ability of the kidneys to handle the body’s water volume, production of hormones that act directly on the blood vessel wall and the health of the arteries, which need to be able to contract and dilate properly.

The smaller the capacity of the vessels to self-regulate according to the volume of blood present, the greater the risk that the patient will develop hypertension. The most serious cases are usually those in which the patient has a real excess of volume and their vessels are unable to dilate to cope with the increased pressure on their walls.

What are systolic and diastolic blood pressure?

In order for us to understand what a normal blood pressure is, we first need to understand how we describe pressure values. For example, do you know what it means to say that a patient has a blood pressure of 120/80 mmHg?

The heart pumps blood through its beats. When the heart contracts, it expels blood from its interior towards the vessels. When it relaxes, it fills with blood again. This alternation of contraction and relaxation occurs, on average, 60 to 100 times per minute. The heart fills and empties, fills and empties… The pressure under the artery walls is pulsatile, that is, it increases in the contraction phase of the heart and decreases in the relaxation phase.

The contraction of the heart muscle is called systole. Therefore, systolic pressure is that which occurs during systole. Relaxation of the heart muscle is called diastole, so diastolic pressure is that which occurs during diastole. Blood pressure is at its highest during systole and lowest during diastole. Hence, they are also called maximum pressure and minimum pressure.

Blood pressure measurement is described under the unit millimeters of mercury (mmHg). Therefore, if the patient has a blood pressure of 120/90 mmHg, this means that the maximum pressure on the artery wall, which occurs during systole, is 120 mmHg and the minimum pressure, which occurs during diastole, is 80 mmHg.

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The lay public often calls it 12/8 (12 by 8), but actually the correct form is 120/80 (120 by 80), as this is the pressure value in millimeters of mercury.

Normal pressure values

What is normal blood pressure?

Our arteries have been programmed to work within certain pressure ranges. When the arteries are subjected to prolonged pressure levels that are too high, the excess tension on their walls begins to cause serious damage.

Small cracks in the wall may appear, facilitating the disruption of small vessels and the formation of calcium plaques in larger arteries. These plaques, in addition to reducing the artery’s own elasticity, also reduce the internal caliber, favoring the occlusion of the circulation by thrombi, an event called thrombosis.

In addition to damage to blood vessels, excessive blood pressure also increases the work of the heart, which must pump blood against increased resistance. After years of overwork, the heart begins to dilate, leading to heart failure .

Normal blood pressure is therefore one in which the arteries are not under stress and the heart is not overloaded. Currently, blood pressure levels for adults, seniors and adolescents are divided as follows:

  • NORMAL BLOOD PRESSURE – patients with systolic pressure less than 120 mmHg and diastolic pressure less than 80 mmHg.
  • PRE-HYPERTENSION – patients with systolic pressure between 120 and 129 mmHg or diastolic pressure less than 80 mmHg.
  • STAGE 1 HYPERTENSION – patients with systolic pressure between 130 and 139 mmHg or diastolic pressure between 80 and 89 mmHg.
  • STAGE 2 HYPERTENSION – patients with systolic pressure above 140 mmHg or diastolic pressure above 90 mmHg.
  • HYPERTENSIVE CRISIS – patients with systolic pressure above 180 mmHg or diastolic pressure above 110 mmHg.

The values ​​described above are used to diagnose and classify hypertension, however, they are not a target for treatment. In hypertensive patients using medication, the values ​​we want to achieve are:

  • Adolescents and adults: blood pressure should be below 140/90 mmHg.
  • Adults with diabetes and/or chronic kidney disease: blood pressure should be below 130/80 mmHg.

Normal values ​​in children

The definition of hypertension in children is more complex, as it depends on the height percentile at which it is found. For example, a 5-year-old child who is in the 10th percentile for height is considered hypertensive if they persistently have values ​​above 109/70 mmHg. A child, also 5 years old, but in the 90th percentile of height often needs to have values ​​above 115/74 mmHg to be diagnosed with hypertension.

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There are tables with acceptable blood pressure values ​​according to age and with the 5th, 10th, 25th, 50th, 75th, 90th and 95th percentiles of height. There are dozens of possible values, so nobody knows them by heart. After measuring the child’s pressure, it is necessary to define which percentile of height he is in to be able, through the table, to interpret his blood pressure levels.

Normal blood pressure in pregnant women

Blood pressure values ​​in pregnant women should be the same as in adults in general. Therefore, it is normal for a pregnant woman to have a pressure lower than 140/90 mmHg.

However, despite the blood pressure reference values ​​being the same, the indication to start treatment with medications is different, as there are no clear benefits with very strict blood pressure control in pregnant women, and there is still the risk of side effects for the fetus .

In pregnant women there are three types of hypertension:

  • Hypertension onset during pregnancy.
  • Chronic hypertension, preexisting before pregnancy.
  • Pre-eclampsia / eclampsia.

If hypertension is recent onset, that is, it did not exist before and appeared during pregnancy, most physicians choose not to indicate treatment with medications, unless the values ​​are above 160 mmHg of systolic pressure or 110 mmHg of diastolic pressure. If, after 12 weeks of delivery, hypertension is still present, then drug treatment should be considered for women with blood pressure above 140/90 mmHg.

If the patient was already hypertensive before becoming pregnant, she should continue the treatment of hypertension, being careful not to use drugs that could harm the fetus. However, if the patient during pregnancy has blood pressure levels below 120/80 mmHg, the medications can be reduced or suspended, as long as the pressure values ​​do not exceed 150/100 mmHg.