Blood pressure is the pressure occurring in the vessels, which is determined by the cardiac output, vascular resistance and blood viscosity (viscosity) of the blood. According to the German Hypertension League, approximately 35 million people in Germany are affected by hypertension (high blood pressure) and have to measure their blood pressure regularly. While a blood pressure value of less than 140/90 mmHg is considered normal for occasional blood pressure measurement by a doctor, the limit value for blood pressure self-measurement is 135/85 mmHg. For classification/definition of hypertension, see below.
Procedures
One can distinguish direct from indirect blood pressure measurement:
- In direct blood pressure measurement, the pressure is measured through a recumbent vascular catheter.
- Indirect measurement:
- According to Riva-Rocci (RR) is performed using a blood pressure monitor (also blood pressure gauge and sphygmomanometer) with a cuff usually on the upper arm or wrist* . In the indirect measurement, the blood pressure is determined either auscultatorisch (ascertainable by listening) with a stethoscope, by pulse buttons or via ultrasound Doppler.The principle is based on the compression of the artery in the five different phases of the measurement and resulting sound phenomena (Korotkow tones).
- Cuffless blood pressure measurement by determining the pulse wave transit time, for example, from the heart to the index finger. In this case, the timing of the heart contraction is determined electrocardiographically. The measurement on the finger is recorded as a photoplethysmographic signal. Thus, blood pressure can be measured from heartbeat to heartbeat. Note: According to one study, measuring devices that determine pulse wave travel times provide higher pressure values on average than cuff devices. Further studies are to be awaited.
* A study in the very elderly (> 75 years) has shown that wrist measurement is not suitable in patients with atherosclerosis (ABI < 0.9) or impaired renal function (GFR < 60 ml/min), as it measures systolic blood pressure values that are too low. Regular blood pressure measurement should be performed to establish the diagnosis of hypertension (high blood pressure).
Before blood pressure measurement
According to the German Hypertension League, the following measures should be followed when measuring blood pressure:
- Always measure at the same time in the morning and evening.
- For hypertension patients taking medication.
- Should have their blood pressure measured in the morning before taking pills and in the evening before going to bed.
- Is before and after therapy intensification to provide a pressure measurement in standing (eg, after one minute) (applies to older hypertensives).
- Perform measurement while sitting and at rest (sit quietly for five minutes).
- The environment should be quiet, do not cross your legs.
- Place the arm to be measured on the table.
- The lower edge of the blood pressure cuff of an upper arm meter should end 2.5 cm above the elbow (cuff at heart level). Attention should be paid to the correct size of the blood pressure cuff: If it is too small, a too high blood pressure value is determined.
- When measuring with a wrist blood pressure monitor is essential to ensure that the measurement cuff is at heart level.
- If the blood pressure values on both arms are different, the higher blood pressure value applies.
- Repeat measurement (at least 2 measurements in a row).
- After one minute at the earliest
- With indication of the lower value
Furthermore, blood pressure measurements should always be taken on both arms. False high measurements when:
- Failure to observe the position of the body:
- When lying down, systolic blood pressure is 3 to 10 mmHg higher than in a sitting position
- An unsupported back can increase systolic blood pressure by 5 to 10 and diastolic blood pressure by 6 mmHg
- Crossed legs during blood pressure measurement can increase systolic blood pressure by 5 to 8 mmHg and diastolic blood pressure by 3 to 5 mmHg
- Has not been sitting quietly for 5 minutes
- Measurement below the level of the heart
- Too short or too narrow cuff (under-cuffing) [common in athletes].
Measurement results
The following values are important in blood pressure measurement:
- Systolic blood pressure – maximum blood pressure value resulting from the systole (contraction/extension and ejection phase of the heart) of the heart.
- Norm: < 120 mmHg
- Mean arterial pressure (MAD; mean arterial pressure (MAP)) – lies between the systolic and diastolic arterial pressures.
- Approximate calculation for:
- Arteries near the heart: MAD = diastolic pressure + 1/2 (systolic pressure – diastolic pressure), i.e., here the MAD approximates the arithmetic mean.
- Arteries far from the heart: MAD = diastolic pressure + 1/3 (systolic pressure – diastolic pressure).
- Norm: 70 to 105 mmHg
- Approximate calculation for:
- Diastolic blood pressure – lowest blood pressure value occurring during diastole (relaxation and filling phase) of the heart.
- Norm: < 80 (80-60) mmHg
- Blood pressure amplitude (pulse pressure amplitude; also called pulse pressure, pulse pressure (PP), or pulse wave pressure; English : Pulse Pressure Variation, PPV) – indicates the difference between systolic and diastolic blood pressure.
- Norm: – 65 mmHg
Interpretation of blood pressure amplitude
| Blood pressure amplitude | Assessment | Comments |
| – 65 mmHg | normal | In one study, morbidity (incidence of disease) increased even at blood pressure amplitudes above 50 mmHg |
| > 65 and ≤ 75 mmHg | Slightly elevated | In the PROCAM cohort, men with a blood pressure amplitude greater than 70 mmHg had a 12.5% 10-year risk of coronary artery disease (CAD; coronary artery disease), compared with 4.7% when the blood pressure amplitude was less than 60 mmHg. |
| > 75 and ≤ 90 mmHg | Moderately elevated | |
| > 90 mmHg | Strongly elevated |
Definition/classification of blood pressure values (German Hypertension League)
| Classification | Systolic blood pressure (in mmHg) | Diastolic blood pressure (in mmHg) |
| Optimal blood pressure | < 120 | < 80 |
| Normal blood pressure | 120-129 | 80-84 |
| High normal blood pressure | 130-139 | 85-89 |
| Mild hypertension | 140-159 | 90-99 |
| Moderate hypertension | 160-179 | 100-109 |
| Severe hypertension | ≥ 180 | ≥ 110 |
| Isolated systolic hypertension | ≥ 140 | < 90 |
More hints
- A “high blood pressure” can only be spoken of after blood pressure has been measured at least three times at different points in time.
- At night, blood pressure physiologically drops by about 10 mmHg. In about two-thirds of all secondary forms of hypertension, this blood pressure reduction is absent (so-called “non-dipper”) or is reduced.
- A meta-analysis could show: Those who did not dip had a significantly higher cardiovascular risk. Those who dipped only a little also had a worse cardiovascular prognosis. Depending on the defined endpoint (coronary events, apoplexy (strokes), cardiovascular mortality (death rate), and all-cause mortality), event rates were up to 89% higher; even reduced dippers still had a statistically significant increased risk of 27%.
Blood pressure difference between the two arms
A blood pressure difference between the two arms of > 10 mmHg is already at greatly increased risk for stenosis of the subclavian artery and peripheral, cerebral, or cardiovascular vascular disease.Blood pressure differences between the two arms are found in:
- Aortic arch syndrome (stenosis (“vasoconstriction”) of several or all arteries branching from the aortic arch, with or without involvement of the aortic arch).
- Unilateral subclavian artery stenosis (narrowing).
- Thoracic aortic dissection (splitting (dissection) of the wall layers of the aorta).
Differences in systolic blood pressure between the two arms should be evaluated as follows:
- Difference in systolic blood pressure of more than 10 mmHg indicates:
- High risk of asymptomatic peripheral vascular disease (vascular disease).
- Difference in systolic blood pressure of more than 15 mmHg indicate:
- Peripheral arterial disease (pAVD) in the legs: relative risk 2.5 (95 percent confidence interval: 1.6-3.8)
- Cerebrovascular disease (disease of the cerebral vessels) (relative risk 1.6; 1.1-2.4).
- Heart disease
- 70% increase in risk of dying from myocardial infarction (heart attack) or apoplexy (stroke)
- 60% increase in risk of a lethal (fatal) event from other causes.
Further notes
- If the blood pressure cuff does not fit around the upper arm of an overweight patient (upper arm circumference of at least 35 cm, BMI of 30 or more, or body fat percentage of at least 25% (men) or 30% (women)), the wrist should be selected for measurement (sensitivity of 0.92 with equally high specificity).
- A meta-analysis of 123 studies with a total of about 614,000 patients examined the extent to which systolic blood pressure correlates with the incidence (frequency of new cases) of cardiovascular events: Each 10-mmHg reduction in systolic blood pressure resulted in a reduction in the relative risk of:
- Major adverse cardiac events (MACE): 20%.
- Coronary artery disease (disease of the coronary arteries): 17%.
- Apoplexy (stroke): 27 %
- Heart failure (cardiac insufficiency): 28 %
- All-cause mortality (mortality rate): 13%.
- Diastolic blood pressure of < 60 mmHg and systolic blood pressure ≥ 120 mmHg (1.5-fold risk of coronary artery disease; 1.3-fold risk of increased mortality (death rate); at baseline blood pressure in the ARIC study).
- Pressures in diastole
- ≥ 80 mmHg increased the risk of apoplexy (stroke) and heart failure (heart failure); ≥ 90 mmHg for myocardial infarction (heart attack).
- < 70 mmHg increased the risk of the combined end point occurring by approximately 30%, mortality (death rate) by 20%, myocardial infarction by 50%, and heart failure by nearly 2-fold
- Blood pressure variability (blood pressure fluctuations):
- Patients with marked measurement-to-measurement variability in blood pressure values are at increased risk for cardiovascular events. Patients with the most pronounced variability in systolic values showed a significantly higher risk of related endpoint events (cardiovascular-related death, myocardial infarction (heart attack), apoplexy (stroke)) compared with those with the relatively lowest variability (hazard ratio for highest versus lowest tercile: 1.30, p = 0.007).
- OXVASC trial: increased variability in beat-to-beat systolic blood pressure was significantly associated with increased risk of stroke recurrence even after adjustment for absolute blood pressure and other established cardiovascular risk factors (hazard ratio, 1.40; 95% CI, 1.00-1.94; p = 0.047).
- Associated with the lowest event rates (risk for myocardial and cerebral infarction, hospitalization for heart failure, all-cause mortality) while on medication:
- Optimal systolic range: 120-140 mmHg
- Diastolic optimal range: 70-80 mmHg
- In the Masked Hypertension Study, it was shown that practice measurements underestimated rather than overestimated blood pressure (= masked hypertension). The practice values of healthy participants were on average 7/2 mmHg lower than their values in the 24-hour ambulatory blood pressure measurement (ABPM). This particularly affected younger, lean individuals. In more than one-third of the study participants, the systolic ambulatory value exceeded the practice value by more than 10 mmHg. A 10 mmHg higher practice blood pressure than the ABPM value occurred in only 2.5% of participants.Conclusion: white coat hypertension thus receives a different status than in the past.The prevalence of white coat hypertension in Germany is about 13%.
- Blood pressure decreases as a function of age at death:
- Age at death 60 to 69 years: blood pressure decrease 10 years before death.
- Age at death 70 to 79 years: blood pressure decline 12 years before death.
- Age at death 80 to 89 years: blood pressure decline 14 years before death.
- Age at death > 90 years: blood pressure decline 18 years before death.
In two-thirds of all patients, the systolic value decreased by more than 10 mmHg (age at death 50-69 years: 8.5 mmHg; age at death > 90 years: 22.0 mmHg).