What can distort blood pressure measurement?
When measuring blood pressure on your own, several things must be considered to obtain accurate readings. It is well known that measurements should be taken in a state of rest - both physically and mentally - while sitting or lying down. It is also easy to understand that one should measure before taking their medications. Only then can comparable values be found.
But why should one not speak during the measurement? How can breathing influence the process, and why should one not smoke beforehand? What happens if the arm is held too high or too low when using a wrist device? We have looked into these and other questions.
Is it necessary to take off the jacket, sweater, and similar clothing for measurement?
Every blood pressure cuff contains a sensor. In most cuffs, this operates on the oscillometric principle - it detects the vibrations of the pulsating blood that occur when the cuff is inflated and deflated. From this, the blood pressure is calculated. If there is a thick sweater, a jacket, or one or more folds of fabric (for example, with wide sleeves) between the sensor and the artery, the sensor can no longer detect these vibrations, leading to incorrect measurements.
Therefore, the arm must be freed for measurement. Only clothing with really thin, body-hugging sleeves may possibly be kept on.
Is it sufficient to roll up the sleeve of a sweater, shirt, blouse, or similar?
This question mainly concerns measurements with an upper arm device. However, even when using a wrist device, a rolled-up or pushed-up sleeve can distort the measurement. This is because rolling up or pushing up the sleeves can constrict them, or the narrow cuffs of the sleeve may not fit well at thicker parts of the arm. If the arm is constricted or tightly compressed, a narrowing of the arteries occurs even before the blood pressure cuff, and the measurement may no longer yield realistic results. Therefore, only clothing that is wide enough should be rolled up or pushed up.
The right cuff is important!
The blood pressure cuff - that is, the part of the measuring device that is applied to the upper arm or wrist - must fit you. Both the length and the width of the cuff must be suitable for your upper arm or wrist. The problem of an ill-fitting cuff occurs more frequently with upper arm devices than with wrist devices.
The width of the upper arm cuff should be chosen so that it can be applied two to three centimeters above the elbow crease. In length, the cuff must fit well around your upper arm. Many cuffs have a marking that indicates whether the cuff fits. Often, an additional marking helps to find the correct position of the cuff so that the sensor is over the artery and can record the vibrations. A cuff that is too wide or too short may yield falsely elevated values. In case of doubt, it is advisable to measure the upper arm or wrist circumference before purchasing a device and to include this in the selection process.
What happens if the measurement point is too high or too low?
Why should one not speak during the measurement?
Speaking in this context is to be seen as a strain that can increase blood pressure values. The body is therefore not in a state of rest. Additionally, the measuring device itself can be disturbed by speaking during the measurement process, causing the measurement to abort or incorrectly detect an arrhythmia.
Why should one not move during the measurement?
How does breathing affect blood pressure?
You should continue to breathe in your normal rhythm during blood pressure measurement to obtain realistic values. The type of breathing can influence blood pressure. Therefore, breathing exercises can be used in the therapy of high blood pressure. Deep, calm breathing can lower blood pressure - even in the short phase of blood pressure measurement. Conversely, if you breathe quickly, shallowly, or strained, blood pressure may increase. Even if one might be able to cheat a little this way to see lower values on the display, one should be aware that these do not reflect the actual blood pressure. Therefore, please continue to breathe normally while measuring your blood pressure.
Why should one not measure immediately after eating?
Why should one not smoke before measuring blood pressure?
Information about the long-term effects on blood pressure can be found in our article „Why does smoking promote high blood pressure?“.
Does it affect the measurement if one drinks coffee or tea beforehand?
About half an hour before the measurement, no coffee or black or green tea should be consumed. The contained caffeine (coffee) or theobromine (black and green tea) can lead to an increase in blood pressure. Individually, this increase in blood pressure can be up to 20 mmHg. This mainly affects people who only occasionally consume these beverages. Those who regularly drink coffee or black or green tea often experience a habituation effect. However, this is also individually different and can be minimal. Therefore, blood pressure should be measured no earlier than 30 minutes after a cup of coffee/tea.
Why should one not measure after consuming alcohol?
Why should one not measure with a full bladder?
A full bladder is also a stress factor. During the filling phase of the bladder, the sympathetic nervous system is activated. This puts the body in a state of heightened readiness - but it also causes constriction of the blood vessels. This can lead to an increase in blood pressure.
Therefore: If the bladder is full, go to the toilet first and then measure blood pressure in a relaxed manner.
Therefore: If the bladder is full, go to the toilet first and then measure blood pressure in a relaxed manner.
Why should one not take a bath before measurement?
A warm or even hot bath in the bathtub lowers blood pressure. The warm water causes the body to relax. The blood vessels dilate, and blood pressure decreases. The water pressure, on the other hand, supports the return of blood to the heart. This stimulates the excretion of fluid through the kidneys via hormonal regulation and also supports the normalization of blood pressure in this way. This relaxing effect can indeed help to lower blood pressure in the long term with regular baths. For this reason, a warm bath is not recommended shortly before a measurement, as everyday values should be reflected in the measurement.
Why does the ambient temperature play a role?
Blood pressure measurement should therefore take place in normally tempered rooms whenever possible.
Why should one not perform two measurements immediately one after the other?
During blood pressure measurement, the artery in the arm is compressed by inflating the cuff until no blood flows through for a short time. As the air in the cuff is slowly released, blood increasingly flows through the vessel again, allowing the blood pressure measurement to take place. After the measurement, the vessel is fully opened again, and blood can flow through unhindered. Nevertheless, one should allow one to two minutes to pass between two measurements to ensure that the vessel has returned to its normal width and that a state of rest has been achieved. According to guidelines, measurements should be taken twice at intervals of one to two minutes.
Sources
- https://www.ncbi.nlm.nih.gov/pubmed/16231755
- https://www.aerztezeitung.de/Medizin/Verfaelschte-Blutdruck-Werte-275577.html
- https://www.herzstiftung.de/Kaffee-Blutdruck.html
- http://flexikon.doccheck.com/de/Sympathikus
- https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2824754?guestAccessKey=f167dda3-8cad-4f34-99ca-79865446c64f&utm_source=for_the_media&utm_medium=referral&utm_campaign=ftm_links&utm_content=tfl&utm_term=100724
By Sabine Croci.
This article is medically reviewed. Last updated (10/2024).
Information on the website and within the app cannot replace a consultation with a doctor, but can certainly complement it.
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