Blood pressure

Synonyms and acronyms: RR (after the inventor of the blood pressure cuff Scipione Riva-Rocci), vascular pressure.

Blood pressure is the pressure exerted by the circulation of the blood on the vessel walls of the body and lung circulation.¹ In everyday medical practice, this is usually understood to mean the arterial blood pressure of the large arteries.² Along with other vital parameters, blood pressure provides information about a person’s health. In the long run, high blood pressure in particular can be dangerous to health.

The systolic blood pressure corresponds to the upper blood pressure value (in the above example: 120 mmHg) and indicates the maximum pressure in the heart ejection phase (tension phase = systole).

Der systolische Blutdruck entspricht dem oberen Blutdruckwert (im oben genannten Beispiel: 130 mmHg) und zeigt den maximalen Druck in der Herzauswurfphase (Anspannungsphase = Systole) an.

The diastolic blood pressure, on the other hand, corresponds to the lower blood pressure value (in the above example: 80 mmHg) and indicates the minimum pressure in the heart filling phase (relaxation phase = diastole).

Depending on age, different blood pressure values are considered “normal”. If there are deviations, the systolic and diastolic values are usually either increased or decreased together. However, there can also be a deviation of only one of the two values.³

Table 1: Blood pressure values- reference range:⁴

Too high blood pressure is called hypertension.⁵

According to the European guideline, this is defined as blood pressure values of 140/ 90 mmHg or higher at rest. Since hypertension is common (average prevalence in adulthood: 50%)⁶ and is a strong risk factor for cardiovascular disease, it is clinically more relevant than low blood pressure.⁷ What makes the diagnosis and understanding of the disease particularly difficult is that the disease is asymptomatic in patients and is often diagnosed late. Treatment of hypertension is essential, however, because hypertensive crises with systolic blood pressure values > 180-230 mmHg can have serious consequences such as cerebral hemorrhage.

In the long term, multiple end-organ damage such as hypertensive retinopathy (eye), myocardial infarction (heart), stroke (brain) or nephropathy (kidney) can occur. A study conducted by Ebinger J. et al (2022) also showed that the risk of hospitalization is twice as high for hypertensives in the case of infection with the omicron variant of SARS-CoV-2 despite triple vaccination. It should be emphasized that hypertension alone, without other chronic conditions such as heart failure or diabetes, was responsible for a more severe course of covid-19 in the study.⁸

Both the start of treatment and the setting of the target blood pressure depend on the overall risk assessment. A change in lifestyle is essential for reducing blood pressure: alcohol and nicotine should be avoided as far as possible and in most cases additional weight loss is recommended. Drug therapy (ACE inhibitor/sartan and diuretic/calcium antagonist) can also be induced.⁹

Blood pressure values below 100/60 mmHg are considered too low and are called hypotension.

Possible symptoms of hypotension are mainly an increased pulse (tachycardia), dizziness, headache, pallor, involuntary muscle tremor, fatigue, lack of concentration and orthostatic dysregulation. Orthostatic hypotension is manifested by the dropping of blood into the legs when changing posture from lying to standing (orthostasis). The reason for this is that the body’s nerves cannot maintain the state of tension against gravity.¹⁰

Low blood pressure mainly affects younger people, especially women. In contrast to hypertension (see above), there is only a need for action such as drug therapy in the case of hypotension if the patient’s symptoms cause increased suffering. However, since low blood pressure can also be caused by diseases such as heart valve defects, anemia or adrenal dysfunction such as Addison’s disease, this should also be investigated in the long term. Measures such as sufficient fluid intake (2 – 2.5 liters per day), alternating showers, sauna sessions, physical training, sufficient night sleep and stays in regions such as the North Sea or the high mountains can help against low blood pressure.¹¹

Hypotension can be categorized as follows:

1. Primary hypotension: idiopathic (with no identifiable cause), in people with slender builds, often occurs along with physical inactivity.
2. Secondary hypotension: endocrine (related to the endocrine system), cardiovascular, or drug causes (e.g., beta-blocker administration), hypovolemia (volume deficiency), or infection.

Along with body temperature, blood oxygen saturation and heart rate, blood pressure is another important vital sign that helps to gain an even deeper insight into a person’s health. Deviations from the normal values, especially if they deviate significantly upwards, are often the cause of many cardiovascular diseases such as heart attacks and thus represent a major risk factor for health. But even a very low blood pressure can provide information about the current state of health.

Underlying diseases of the kidneys, thyroid or blood vessels can be the cause of high blood pressure in 10-15% of hypertensive patients. One of the causes, for example, is primary hyperaldosteronism (Conn’s syndrome). The body, or more precisely the adrenal gland, releases too much aldosterone here, which leads to an accumulation of water and sodium and thus to increased blood pressure.²¹ A study conducted in 2016 showed that 6% of the subjects with hypertension had Conn’s syndrome.²² Hyperthyroidism can also be responsible for high blood pressure. Another relevant factor in the development of hypertension is sleep apnoea syndrome, which is associated with nocturnal breathing pauses. It is reassuring to know that successful treatment of the underlying diseases can also treat hypertension.

There may also be a genetic predisposition to high blood pressure: In this case, there is an increased incidence of high blood pressure in the family and risk factors for high blood pressure are increased as a result.²³

High blood pressure is an important risk factor for the development of many diseases or complications such as end organ damage.²⁴ Some of the diseases are listed below:

• Diseases of the eye:
  • Retinopathy (retinal disease that can severely affect vision)
  • Blindness
• Cardiovascular diseases:
  • Stroke
  • Aortic aneurysm
  • Heart failure
  • Dementia
  • Arteriosclerosis
  • Coronary heart disease
  • Cerebral hemorrhage
  • Peripheral arterial occlusive disease (occlusion of arm or leg arteries, usually due to arteriosclerosis)
  • Heart attack
  • Cardiac arrhythmia with ventricular extrasystoles²⁵
  • Left ventricular hypertrophy (enlarged left ventricle of the heart)
• Diseases of the ears:
  • Hearing loss (statistically higher risk for women)
  • Tinnitus
• Mental illnesses/ diseases of the nervous system:
  • Erectile dysfunction
  • Cerebral circulatory disorder
  • Depression (there is a higher risk of developing depression if blood pressure therapy with calcium antagonists or beta-blockers has been used)
• Diseases of the kidneys and urinary tract:
  • Renal insufficiency
  • Kidney failure
  • Nephropathy with proteinuria (increased protein excretion)²⁶

The level of blood pressure depends on both numerous physiological factors such as age, health status and gender, as well as external conditions, which are described in more detail below.

Blood pressure is subject to large fluctuations during the course of the day, also known as the circadian blood pressure rhythm. Even before waking up in the morning, blood pressure rises continuously, there is a brief low at midday, while it then rises again from 4-6 p.m. and drops again significantly during the night.²⁷ Renal hypertension is often characterized by hypertension at night – and thus by a disturbed circadian rhythm.

In addition, diabetes and hypertension (e.g. secondary forms of hypertension such as sleep apnoea) should also be considered when a disturbed circadian rhythm is detected. A large-scale meta-study showed that elevated blood pressure at night is a major risk factor for heart attack and stroke. They also concluded that blood pressure measurements taken during the day in hypertensive patients, for example in the doctor’s office, are less effective because night-time blood pressure is the most informative for the cardiovascular risk of the respective patient.²⁸

Another study with 18.078 participants also showed that the targeted intake of blood pressure-lowering medication before a night’s rest significantly reduces the risk of cardiovascular disease.²⁹ In contrast, too much lowering of blood pressure was observed in older people with silent reduced blood flow to the brain or heart.³⁰

In addition, studies showed that lack of sleep or poor sleep quality can also increase blood pressure. The reasons for this are increased sympathetic activity and the release of cortisol in the adrenal glands.³¹³²

In the meantime, it is well known that illnesses can have different gender-specific courses. There are also differences in blood pressure between the male and female sexes: in general, it can be said that women’s blood pressure is lower than men’s until their menopause³³ After the menopause, however, this changes. The evaluation of four cohort studies also showed that women had a 25% increased risk of cardiovascular diseases already at systolic blood pressure values of 100-109 mmHg (reference value: 100 mmHg), whereas this was only the case for men from 130-139 mmHg. In addition, the risk of stroke increased in women from a systolic blood pressure of 120 mmHg, while the same risk increased in men from 150 mmHg. Whether there should now be gender-specific standard values remains to be discussed. However, the study shows how important gender-sensitive medicine really is.³⁴

The following table shows the blood pressure values divided by age:³⁵

In contrast to adults, there are no risk-adapted standard values for children, as these change with body growth. For this reason, they are defined in comparison to healthy control groups of the same size and age (percentile curves). If the blood pressure is above the 95th percentile, it is defined as “high blood pressure”.³⁶

Higher than indicated blood pressure in children and adolescents is a growing health problem. If children are diagnosed with hypertension, they should be screened for cardiovascular or renal disease and diabetes mellitus. Effective treatments include weight loss (if overweight), a healthy diet low in salt, exercise and abstaining from alcohol and tobacco. The prevalence of hypertension in children aged 3-18 years is 3.6%.³⁷ The majority of children diagnosed with hypertension also suffer from high blood pressure as adults.³⁸

Due to the hormonal changes, many bodily functions change during pregnancy. As a rule, blood pressure drops slightly, especially at the beginning of pregnancy, and the heart rate is increased. While low blood pressure does not normally pose any risks for the expectant mother and the child, too high blood pressure can be dangerous for both.³⁹ A blood pressure of 140/90 mmHg is set as the limit value.

The following types of hypertension are distinguished in pregnancy (with frequency in percent in each case):

• Chronic hypertension: diagnosed before/during pregnancy (3%)⁴⁰
• Pre-eclampsia: hypertension occurring during pregnancy with proteinuria (5-8%)⁴¹
• Gestosis: pre-eclampsia in women with chronic hypertension (20-25%)
• Gestational hypertension: high blood pressure that manifests after the 20th week of pregnancy and normalizes by 12 weeks after birth (6%).

Risk factors are considered to be general factors such as the presence of autoimmune or renal diseases, obesity, diabetes, older age or chronic hypertension. Multiple pregnancies, gestational diabetes and first births are also pregnancy-associated risk factors.⁴² The pathophysiological cause of hypertension in pregnancy is disturbed placentation⁴³, which poses a risk to the fetus

If preeclampsia is not treated in time, it can lead to placental abruption and/or premature birth. A severe form of pre-eclampsia can also cause organ damage and seizures (eclampsia) in the pregnant woman.⁴⁴ Since high blood pressure during pregnancy poses a great risk to the mother-to-be and the fetus, blood pressure should be checked regularly.

The risk of developing hypertension increases with age because the elasticity of the blood vessels continues to decrease. For this reason, three out of four people between the ages of 70 and 85 are hypertensive. In addition to the loss of elasticity, lifestyle habits in particular also seem to be causative for high blood pressure, as studies show that in indigenous people blood pressure remains constant even in old age.⁴⁵ Treating blood pressure is essential, however, because high blood pressure in old age is also associated with an increased mortality risk. Attempts are made to adjust the systolic blood pressure to below 140 mmHg. Scientists from Ulm examined 1,100 participants and found out that the mortality risk is strongly influenced by the frailty⁴⁶ of the test persons. While the optimal blood pressure in the fitter elderly subjects was 130 mmHg (related to mortality risk), it was surprisingly 160 mmHg in the very frail elderly. This study thus shows the importance of individual adjustment of blood pressure and that physical and mental fitness should be included in the treatment of hypertension.⁴⁷⁴⁸

Blood pressure is generally higher during physical exertion, stressful situations or nervous strain. Under physical stress, the systolic blood pressure rises because the stroke volume of the heart increases – the diastolic blood pressure, on the other hand, remains approximately the same. However, the diastolic blood pressure also rises during maximum exercise. The reason for this is that maximum exercise leads to isometric muscle contraction and, as a result, peripheral vascular resistance increases sharply.⁴⁹

However it is well known that physical activity can lower blood pressure in the long term: while it lowers the sympathetic tone, the vagus tone increases at rest. This lowers the heart rate and dilates the arterial blood vessels. For every kilogram of body weight lost, systolic blood pressure decreases by 1.5-2.0 mmHg and diastolic by 1.2-1.5 mmHg diastolic. Up to 160 mmHg (systolic), blood pressure can be normalized with three times a week exercise to a similar extent as with medication. If the blood pressure is above 160 mmHg, it must first be adjusted with medication to avoid dangerous blood pressure peaks. This is because high blood pressure can be seen as an important risk factor for sudden cardiac death during physical activity. Another study showed that every third person who died from sudden cardiac death was hypertensive. While a few years ago, low-intensity sports such as cycling, jogging or swimming were recommended and strength training was discouraged, more recent studies have shown positive effects on lowering blood pressure through strength training.

However, it is important to know that in the short term, high blood pressure first increases. The important thing here is that certain limits must not be exceeded. The appropriate choice of sport is also important, as certain types of sport trigger blood pressure spikes even in people with normal blood pressure levels. Studies show that regular exercise can greatly reduce the cardiovascular mortality risk in hypertensive patients.⁵⁰ A prospective cohort study over 25 years concluded that the cardiovascular mortality rate was 70% lower in subjects with hypertension who were active in sports than in the control group who were inactive in sports.⁵¹ Blood pressure is generally higher during physical exertion, stressful situations or nervous strain. Under physical stress, systolic blood pressure rises because the stroke volume of the heart increases – diastolic blood pressure, on the other hand, remains approximately the same. Under maximum stress, however, this also rises.

After a meal, on the other hand, blood pressure is somewhat lower. The reason for this is that the human body is busy digesting and the digestive organs are therefore supplied with more blood. The blood volume of the body therefore decreases somewhat and so does the blood pressure. In order to avoid false results, blood pressure should not be measured immediately after a meal.⁵²

However, if the blood pressure drops sharply after a meal, this is called postprandial hypotension. This can result in dizziness, lightheadedness and an increased risk of falling. It usually affects older people with high blood pressure or people who have damaged a center in the brain that controls the autonomic nervous system – i.e. in diseases such as Parkinson’s, Shy-Drager syndrome or diabetes. The reason for this is that blood pressure during digestion cannot be maintained by the blood vessels in other parts of the body. Eating small meals that are low in carbohydrates can help.⁵³

It is often mistakenly assumed that high temperatures can lead to high blood pressure. In fact, the opposite is true: the high temperatures cause dilatation of the vessels and thus blood pressure drops. While hypotension is not dangerous for healthy people, it can cause serious problems for pregnant women and elderly people, as the supply of vital organs or the care of the child can no longer be guaranteed. If, on the other hand, the temperature drops, this becomes a problem, especially for hypertensive patients. The drop in temperature causes the vessels to contract further and the blood pressure rises, as a higher resistance has to be overcome.⁵⁴

Caffeinated drinks should not be consumed before a blood pressure measurement, as they can increase blood pressure by 10-20 mmHg in the short term. A higher increase in blood pressure after coffee consumption can be observed especially in people who drink coffee only occasionally – but with more frequent caffeine consumption, a habituation effect sets in.⁵⁵ The question of whether the consumption of caffeinated beverages increases blood pressure is controversial. A systematic review and meta-analysis (n=172,567) concluded that drinking more than three cups of coffee a day compared to one cup or less was not associated with an increased risk of hypertension. However, a slightly increased risk was found with consumption of 1-3 cups daily.⁵⁶

Im Liegen ist der Blutdruck um 3-10 mmHg höher als im Sitzen. Aus diesem Grund gilt bei gesunden, mobilen Personen die Empfehlung, immer im Sitzen zu messen, um die Messergebnisse nicht zu verfälschen.⁵⁷ Neben der Höhe des Blutdrucks ist allerdings auch seine Stabilität von großer Bedeutung. Eine Studie aus dem Jahr 2006 hat gezeigt, dass bei Personen, deren Blutdruck sowohl im Stehen als auch im Liegen ähnliche Druckwerte aufweist, gemessen an der Sterblichkeit, doppelt so vital waren als diejenigen Probanden, deren Blutdruck vom Liegen zum Stehen deutlich absank. Schlussfolgernd kann ein instabiler Blutdruck als Risikofaktor für Herz-Kreislauf-Erkrankungen angesehen werden.⁵⁸

The HARVEST study found that 15% of hypertension patients had a heart rate over 85 beats and 27% had a heart rate over 80 beats per minute. In addition, a high heart rate was shown to be a risk factor for developing hypertension during the course of the study.⁵⁹

Heart rate variability (HRV), the variation in the time interval between two heartbeats, was also lower in hypertensives than in people with normal blood pressure levels. In addition, the likelihood of developing hypertension was higher when baseline HRV was lower than reference baseline.⁶⁰

In contrast, some hypertensives have a consistently low resting heart rate. The so-called “baroreceptor reflex” is responsible for this: if the blood pressure rises, the parasympathetic nervous system is stimulated via the vagus nerve, the sympathetic nervous system is inhibited and thus the heart rate is lowered due to the negative chronotropic effect. If, on the other hand, the blood pressure drops, the parasympathetic nervous system is inhibited and thus the heart rate is increased.⁶¹

Since blood pressure is an important vital parameter for assessing the current state of health, it should be checked regularly. There are different types of blood pressure measurement available for this purpose.

Fig 2.: Scheme for indirect, bloodless measurement of arterial blood pressure according to Riva-Rocci. Above the arterial blood pressure and the gradually decreasing cuff pressure, below the Korotkow sounds audible in the red area above the brachial artery. Below, sketch of the measurement arrangement.

Indirect blood pressure measurement according to Riva-Rocci uses either a blood pressure cuff on the upper arm and a stethoscope or an electronic blood pressure monitor (oscillometric blood pressure measurement⁶²). Although these applications are somewhat less accurate than direct blood pressure measurement, i.e. the insertion of a measuring probe into the artery, they are used more frequently in everyday clinical practice because of their practicability.

The blood pressure cuff is applied to the upper arm, the valve must be closed beforehand. The stethoscope is placed in the crook of the elbow, it is pumped up quickly until the radial pulse is no longer visible.

Next, the valve is opened and the air is allowed to escape slowly. While the beginning of the sound represents the systolic value, the diastolic value is displayed when the sound disappears.

The principle of indirect blood pressure measurement works as follows: By compressing with a cuff, the blood flow in the brachial artery⁶³ is stopped until the pressure of the cuff is greater than the systolic blood pressure and no flow noise can be heard. Air can escape through the valve opening. When the pressures of the cuff and the systolic blood pressure are equal, the blood can flow through the artery again. However, the blood does not flow continuously because the diastolic blood pressure is still lower than the cuff pressure. This results in a rhythmic alternation between blood flow (systole) and no blood flow (diastole). This alternation is the cause of the typical pulse-synchronous flow noises, also called Korotkoff noises. The cuff pressure continues to drop, while the valve remains open. If the values are lower than the diastolic blood pressure, no more flow noises are heard because the brachial artery remains open.⁶⁴

Normally, blood pressure is always measured on the same upper arm, at the wrist or in the ear canal, preferably while sitting. When measuring on the upper arm, the cuff must always be placed at heart level.

It is important that the blood pressure measurement is always taken under the same starting conditions.

• To avoid measurement errors, a few things should be considered in advance:
  The blood pressure measurement should always be taken at the same time, as blood pressure is subject to diurnal fluctuations.⁶⁵
• Physical (e.g. pain) and/or emotional stress can strongly influence the blood pressure.
• Noise sources should be minimized and there should be no talking during the measurement.
• The size of the cuff should be appropriate for the patient’s upper arm circumference.
• Tight, constricting clothing should not be worn on the day of the measurement.⁶⁶
• Caffeine and nicotine consumption can falsify the measurement results.
• Antihypertensive medication should not be taken until after the blood pressure measurement.
• The patient should not move and the feet should be placed side by side on the floor.

It is also important to note that the values measured in a doctor’s office are not always medically correct. One reason for this can be so-called white coat hypertension. Since the patient is excited when visiting the doctor, the blood pressure values are often higher than when measured at home.⁶⁷