Introduction
Technical procedures are used to determine the pressure in a blood vessel when measuring blood pressure. A distinction is made between the measurement of arterial and venous pressure. Since the measurement of arterial pressure is a very simple method, it plays a very important role in everyday medical life. Various methods can be used to measure pressure.
How is the blood pressure measured?
Blood pressure provides us with important information about the pressure in the blood vessels and about the function of the cardiovascular system. When measuring blood pressure, a distinction is generally made between systolic and diastolic blood pressure. The systolic value is always the higher of the two.
When the heart contracts and pumps blood into the body, the systolic value is determined. During the diastolic value, the heart relaxes and fills with blood again. The blood pressure should be measured at rest.
To measure blood pressure, an inflatable cuff is usually attached to the upper arm, approximately at heart level. The cuff should be neither too narrow nor too wide, depending on the patient’s arm circumference. Cuffs that are too wide measure values that are too small and cuffs that are too narrow measure values that are too high.
Blood pressure can be measured on both the left and right arm, or should ideally be checked on both sides to rule out a lateral difference that could indicate vascular occlusion. It is best to measure blood pressure in the morning and before taking antihypertensive medication, as it is often too high in the morning. The method of indirect blood pressure measurement using a blood pressure cuff was developed by the physician Riva-Rocchi and therefore bears the initials RR.
By inflating the cuff, the artery of the upper arm is completely squeezed so that no more blood can flow through it. The pressure should be built up to such an extent that the values are safely above the expected systolic blood pressure. The pressure is then released from the cuff.
At the same time, the examiner uses a stethoscope to listen to the artery in the crook of the arm. Once the systolic pressure is reached, blood can flow through the vessel again. However, since the vessel is not yet fully opened, it flows turbulently and produces the so-called Korotkow sounds, which can be heard on the artery with a stethoscope.
The sounds stop when the diastolic pressure is reached. At the time of diastolic pressure, the vessel is fully open again and the blood can flow smoothly through the artery again without producing Korotkov sounds. In order to get a statement about the daily course of the blood pressure, a 24-hour measurement can be ordered by the doctor, during which the blood pressure is measured every 15 to 30 minutes.
There are also digital devices for the patient to measure himself, which make it much easier to measure the blood pressure. Patients usually have digital devices that are also applied to the upper arm. It is also important to ensure that the cuff is applied at heart level and that the measurement is taken while sitting or lying down.
In contrast to the manual measuring method, the blood pressure values of digital measuring devices are displayed directly on the device. Inflation is also automatic. Furthermore, there are also invasive or direct methods of measuring blood pressure, in which a pressure sensor is inserted directly into a vessel.
This allows the blood pressure to be monitored more accurately and continuously, which is particularly useful in intensive care medicine. In general, there are blood pressure monitors that measure either on the wrist or the upper arm. If the device is correctly adjusted and used absolutely according to the instructions, it makes no difference where you measure your blood pressure.
However, in reality this is rarely the case and errors are much more common when measuring at the wrist. This is mainly due to the fact that the cuff should be continuously at heart level during the measuring process. With the upper arm, this is easy to achieve by sitting still and letting the arm simply hang.
When measuring at the wrist, however, the arm must be held at the correct angle. This angle is often chosen incorrectly and is not maintained for the entire time of the measurement. This measuring error can then vary so much from day to day that the values are no longer comparable and the blood pressure measurement is carried out for free.
The only error that can occur when measuring on the upper arm is that the blood pressure values measured are too high due to a cuff that is too narrow in thicker people. When buying a blood pressure monitor, it is therefore best to use an upper arm monitor and get advice on the size and width of the cuff. The question of which arm to measure on varies from person to person and depends on where the blood pressure was higher when you first measured it.
So if you are new to measuring your blood pressure regularly with a home device or change to another device, you should measure on both arms the first time you use it. If your blood pressure is higher on your left arm than on your right, you should always measure on your left arm in the future. If it is higher on the right, then on the right.
Of course, it is also possible to take a measurement on both arms each time, but this requires considerably more time and is therefore not suitable for everyday use. When you are standing or sitting, the blood vessels must be tense to a certain degree so that the blood from the legs can get back to the heart. If they were not tense, the blood in your legs would “sink” and you would regularly feel very dizzy.
When you lie down, your legs and your heart are on the same level, which relaxes the muscles around the blood vessels. In addition, the rest of the body relaxes due to the fact that we lie down and are about to sleep or at least rest. This lowers blood pressure.
When we sit up again, the blood pressure rises again together with the pulse to ensure sufficient blood circulation. It can therefore be said that the difference between a blood pressure measurement in a lying position and one in a sitting position is that the blood pressure in a lying position will be lower than that in a sitting position. However, this difference is usually not very high.
It is more important to always measure the blood pressure in the same position, i.e. always lying or sitting. This makes it easier to compare the measured blood pressure values and to detect changes. It makes sense to always measure the blood pressure at the same time of day or always in the morning or evening.
Once a time has been set for the measurement, it should be kept to in the future. The reason for this is our fluctuating hormone balance, which can have a considerable influence on blood pressure. In the morning, the body releases more of the hormone cortisone, which makes us awake and active.
This causes the blood pressure to rise. In the evening, on the other hand, when it gets dark, the hormone melatonin is produced in increased quantities. It makes us tired and ensures that all body functions are shut down.
So also the blood pressure. Therefore, blood pressure values measured in the morning and evening are hardly comparable. In the initial phase after the diagnosis of “high blood pressure” has been made, it should be measured in the morning and evening if possible.
Due to our hormones, blood pressure is subject to natural fluctuations during the course of the day. Measuring in the morning and evening makes it possible to check whether these fluctuations occur regularly or whether there are any disorders that could cause a general increase in blood pressure. After this initial phase, in which the correct dose for any medication must also be found, it is sufficient to take measurements once a day, always at the same time of day.
Thick upper arms only influence the blood pressure measurement if the cuff of the blood pressure monitor is too tight and too narrow. In this case, false high blood pressure values will occur. If, on the other hand, the circumference of the upper arm is measured when purchasing the device and a meter with a larger cuff is chosen accordingly, the thickness of the upper arm no longer has any influence on the measurement result.