Arterial hypertension, also known as high blood pressure, is a very common condition in Brazil. According to the Brazilian Society of Cardiology (SBC), approximately 30% of adults are hypertensive. This number only confirms the importance of knowing how to measure the pressure, understand if it is too low or too high. Medical follow-up is also necessary.
Although blood pressure is an important measure for health, there are numerous doubts that range from standard values to the way of measuring. For example, there is, yes, a right way to position the cuff (the armband) on the arm. In addition, the values obtained through smartwatches must be eventually checked, as they do not replace standard medical devices.
What is Blood Pressure?
Before we continue, it is important to have a very clear understanding of what blood pressure is. It is the pressure that blood exerts on the walls of the arteries during its passage, while it is pumped by the heartbeat through the body.
To measure pressure, regardless of the type of device, two “numbers” are used:
- Systolic blood pressure (SBP): the blood pressure generated by the contraction of the heart, that is, the pressure of blood output to the arteries. It can also be called “maximum pressure”;
- Diastolic blood pressure (DBP): it is the “minimum pressure”, as it measures the force of the blood in the arteries when the heart is “relaxed”.
When is blood pressure high?
“High blood pressure usually does not cause symptoms”, explains Luiz Guilherme Velloso, a cardiologist at the São Camilo Hospital Network in São Paulo. Despite being silent, the doctor recalls that “it ends up resulting, over time, in an increase in the incidence of cardiovascular diseases, kidney disease and retinal changes”. Including, the risks of heart attack and Cerebral Vascular Accident (CVA), also known as stroke, are greater in hypertensive patients, who do not treat their condition.
Now, returning to the measurement of blood pressure, the standard may vary depending on the individual’s age and its peculiarities, but, within the average, an adult is hypertensive when he has a pressure above 140/90 mmHg (or 14 by 9). . For the elderly, the ceiling changes to 15 by 9. In children up to 10 years old, 12 by 8 already configures hypertension.
What is low pressure?
“Blood pressure should only be considered low and let’s have some concern about that when it causes symptoms such as dizziness, visual dimming and cold sweat. If it’s not producing symptoms but blood pressure levels are below 12 over 8 , this should not be a cause for concern”, explains cardiologist Velloso.
Blood pressure table
To specify blood pressure levels, including pre-hypertension, it is possible to consult the table of Brazilian Guidelines on Arterial Hypertension, whose last edition is from 2020. The document is developed by a wide range of specialists and is based on international studies, including meta-analyses — type of research that analyzes results from different studies on the same topic.
Despite the parameters in the table, cardiologist and nutrologist Karla Gouvea makes an important note: “Our blood pressure does not have a fixed value. It fluctuates”. Therefore, a single measurement that is altered is not enough to indicate that the patient is hypertensive. This can only be said from repeated measurements, under ideal conditions, in two or more medical visits, and never from an isolated event. After all, in a few days, the pressure can even fluctuate. “If you run, get scared, are doing physical activity or are feeling pain (like pain in the spine), it will go up”, explains Gouvea.
What is the best way to measure blood pressure?
To measure blood pressure, you need to be quiet and at rest for at least 5 minutes. You also must not have ingested alcohol and, in the last 30 minutes, you must not have drunk coffee, a substance that accelerates your heartbeat. In addition, it is essential that the person does not talk during the measurement.
According to Velloso, “blood pressure should be measured in the non-dominant arm”. This means that if the person is right-handed, the cuff should be placed on the left arm — above the elbow or on the wrist — and vice versa. If the person is sitting, the palm of the hand should be facing upwards with the arm resting on a surface so that it is at the height of the heart. If lying down, the palm is also turned upwards.
However, the cardiologist makes an addendum: “Measurements (of pressure) made on the wrist or on the finger are not completely reliable, and measurement on the arm is more recommended”. And, as we have already explained, the pressure measurement should not be unique. Ideally, three different measurements should be taken, with the lowest being considered.
Smartwatch and free apps to measure blood pressure
Just to let you know, there is no cell phone application that, by itself, measures blood pressure (free or not), in a way recognized by regulatory agencies. What happens is that some apps use the information collected by a smartwatch to measure pressure. In these cases, yes, it is possible to measure it. The first time, the user will normally have to calibrate the device with the help of a cuff.
For example, in Brazil, the National Health Surveillance Agency (Anvisa) recognizes the Samsung Blood Pressure Monitor app (BP Monitor App), linked to the Galaxy Watch. But the agency advises that this meter should not be used to confirm a diagnosis of hypertension, which is up to medical analysis. So, it would be more of a follow-up in today’s understanding, but that could change in a few years.
For Sueli Vieiras, cardiologist at the São Camilo Hospital Network in São Paulo, before using the measurement value from a smartwatch, the advice is to make a comparison with medical devices, within the office itself, for example.
It is worth remembering that, in case of excessively high blood pressure or “strange” symptoms, such as dizziness or headache, the patient should seek medical help. In these cases, he can resort to his own doctor and, if this is not possible, the orientation is to seek prompt assistance.
Source: Brazilian Guidelines on Arterial Hypertension, Anvisa e Brazil Agency
