Ambulatory blood pressure measurement

The phenomenon of blood pressure has been known for almost 2000 years, but it has only been possible to measure it for around 100 years (Vetter 1999).

As early as 1713, Stephan Hales succeeded in taking the first blood-based measurement of blood pressure (Eckert 2006).

Pouseuille developed the first mercury manometer as part of his dissertation in 1821 (Eckert 2006).

In 1896, the Italian Scipione Riva-Rocci presented a blood pressure measuring device with an upper arm cuff and mercury manometer, with which systolic blood pressure could be determined by compressing the brachial artery (Eckert 2006).

Diastolic blood pressure was first determined by the military doctor Nikolai Sergejev Korotkoff, who developed this method as part of his dissertation in St. Petersburg in 1905 (Eckert 2006).

The first self-measurement of blood pressure was carried out by Brown in 1930, and since then it has been known that blood pressure measured at home is lower than that measured in a doctor's office. Self-measurements by patients became increasingly widespread in the 1970s - 1980s (Eckert 2006).

When measuring blood pressure, the arterial pressure in the vessels is measured. This is defined as the blood ejection capacity of the heart, the resistance in the vessels and the capacity or distensibility of the peripheral vascular system (Wormer 2017).

Blood pressure can be measured directly or indirectly (Scholz 2018):

• Blood-based measurement, also known as "direct blood pressure measurement":

This is possible using a Statham pressure transducer in an intensive care unit, during surgery and during a cardiac catheterization (Herold 2025).

• Bloodless measurement, also known as "indirect blood pressure measurement":

This involves 3 different measurement techniques:

- the usual sphygmomanometric measurement method according to Riva-Rocci (Herold 2025)

- the palpatory measurement. After inflating the cuff, the pulse is palpated on the radial artery. As soon as it appears, this corresponds to the systolic blood pressure (Scholz 2018).

- the so-called oscillatory measurement using automatic measuring machines or electronic hand-held measuring devices (Scholz 2018).

Blood pressure can be measured in the doctor's office or independently at home. Blood pressure measurements are possible at rest or under stress, as well as 24-hour long-term measurements (Eckert 2006).

Blood pressure measurement, which is still common today, was only made possible by the combination:

• the stethoscope developed by Laennec
• compression of the brachial artery according to Riva-Rocci
• auscultation of the sound phenomena described by Korotkoff (Eckert 2006).

Carrying out the blood pressure measurement:

• Blood pressure should be measured with the patient lying or sitting down after a 3-5 minute rest period
• The arm on which the measurement is taken should be positioned at heart level and the elbow slightly bent (otherwise the measured values will be approx. 10% higher)
• The lower edge of the blood pressure cuff should be placed approx. 2.5 cm above the crook of the elbow
• A microphone, if present, should be placed above the brachial artery
• The cuff pressure should be inflated to approx. 30 mmHg above the expected systolic pressure
• The pressure is then slowly lowered by 2 mmHg per second (Herold 2018 / Herold 2025)
• If noises are immediately audible, the pressure of the cuff must be released completely and inflated again to higher values after 1-2 minutes
• The systolic value is measured at the first audible Korotkoff murmur and the diastolic value when the Korotkoff murmur disappears
• Blood pressure should be measured on both arms and repeated at least once (Herold 2025)

Indications for blood pressure measurement:

• serves to screen for arterial hypertension
• monitoring the course of arterial hypertension
• As it is a non-invasive examination, it should be part of every physical examination
• A reduction in systolic blood pressure of just 2 mmHg already leads to a 7% reduction in mortality from CHD and a 10% reduction in the risk of suffering an apoplexy (Ertl 2024).

Contraindications to blood pressure measurement:

There are no major contraindications to conventional blood pressure measurement.

However, patients with dialysis shunts are recommended to have the measurement performed on the contralateral arm, as are patients after surgery or radiotherapy for breast cancer with or without lymphedema of the arm (Ertl 2024).

Special features of blood pressure measurement:

• Cuff width

The width of the cuff plays a role in blood pressure measurement. It should be at least 40% of the arm circumference and the length of the cuff should be at least 80% of the arm circumference (Kasper 2015). This results in the following cuff dimensions:

- Arm circumference between 24-32 cm for 13x24 cm cuff size

- Arm circumference between 33-41 cm with 15x30 cm cuff size (Herold 2025)

For much thicker arms, the pressure would otherwise be measured approx. 10 mmHg too high, for very thin arms approx. 10 % too low (Herold 2025).

• Korotkoff tones down to 0 mmHg audible:

This may be the case if

there is an increased HZV or hypercirculation, as is possible, for example:

- anemia

- with fever

- during pregnancy (Herold 2018)

- in the case of a large AV fistula

- in the case of severe aortic regurgitation (Kasper 2015)

In this case, the diastolic value should be read in phase IV (see Korotkoff murmurs), i.e. as soon as the sound becomes quieter (Herold 2018).

Quiet Korotkoff sounds

Auscultation can be difficult in very thin, seriously ill or elderly patients. In such cases, before inflating the cuff, it is advisable to raise the patient's arm above the patient's head height for approx. 30 seconds while the hand opens and closes 5-10 times. The regular measurement is then carried out. As a rule, the tones can then be heard more clearly without affecting the blood pressure (Campbell 2023).

Measuring blood pressure on the thigh

In the case of hypertensive blood pressure values, the pulse on the femoral artery should always be measured as well. If this is weakened, there is a suspicion of aortic coarctation. This suspicion can be checked by measuring the blood pressure in the lower extremities. The blood pressure there is generally 30-40 mmHg higher than in the upper extremities. If hypotension is found in the legs with hypertension in the arms, this is an indication of aortic coarctation and requires further diagnostics (Herold 2025).

Advanced arteriosclerosis

Arteriosclerosis causes stiffness of the vessel wall, which leads to a demonstrable underestimation of systolic blood pressure (Campbell 2023).

The noise itself is caused by the natural resonance of the equivalent spring-mass-damper system. The optimal systolic endpoint is the occurrence of Korotkoff murmurs, the optimal diastolic endpoint is their disappearance (Babbs 2015).

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