Sphygmomanometer: what it is and how to use it (to measure pressure)

The sphygmomanometer is a device widely used by health professionals to measure blood pressure, being considered one of the most reliable methods to assess this physiological value.

Traditionally, there are 3 main types of sphygmomanometer:

Aneroid: they are the lightest and most portable, which are normally used by health professionals at home with the help of a stethoscope; Mercury: they are heavier and, therefore, are generally used inside the office, also in need of a stethoscope. Since they contain mercury, these sphygmomanometers have been replaced by aneroids or fingerprints; Digital: they are very portable and the easiest to use, without the need for a stethoscope to obtain the blood pressure value. For this reason, they are the ones that are normally sold to non-health professionals.

Ideally, to obtain the most accurate blood pressure value, each of these types of sphygmomanometers should be calibrated regularly, with the possibility of using the device manufacturer or some pharmacies.

Aneroid sphygmomanometer

How to use the sphygmomanometer correctly

The way of using the sphygmomanometer varies according to the type of device, with aneroid and mercury sphygmomanometers being the most difficult to use. For this reason, these devices are generally used by health professionals trained in the technique.

1. Aneroid or mercury sphygmomanometer

To measure blood pressure with this type of device, you must have a stethoscope and follow the steps below:

Put the person sitting or lying down, in a comfortable way so that it does not generate stress or nervousness, as it can change the blood pressure value; Support one arm with the palm facing upwards so as not to put pressure on the arm; Remove items of clothing that can squeeze the arm or that are too thick, the ideal being to measure with the arm bare or just with a thin layer of clothing; Identify the pulse in the fold of the arm, in the region where the brachial artery passes; Place the clamp 2 to 3 cm above the fold of the arm, tightening it slightly so that the rubber cord is at the top; Place the head of the stethoscope on the wrist of the arm fold, and hold it in place with one hand; Close the sphygmomanometer pump valve with the other hand and fill the cuff until it reaches about 180 mmHg; Open the valve slightly to empty the cuff slowly, until you hear small sounds in the stethoscope; Record the value that is indicated on the sphygmomanometer manometer, as this is the maximum blood pressure, or systolic; Continue to slowly empty the cuff until no more sounds are heard on the stethoscope; Record the value indicated on the manometer again, as this is the minimum blood pressure, or diastolic value; Completely empty the sphygmomanometer cuff and remove it from the arm.

Since the step-by-step to use this type of sphygmomanometer is more complex and requires more knowledge, generally its use is only done in hospitals, by doctors or nurses. To measure blood pressure at home, the easiest is to use a digital sphygmomanometer.

2. Digital sphygmomanometer

Digital sphygmomanometer

The digital sphygmomanometer is the easiest to use and, therefore, it can be used at home to check blood pressure regularly, without needing to be used by a health professional.

To measure the pressure with this device, just sit or lie down comfortably, support the arm with the palm facing up and then place the device clamp 2 to 3 cm above the arm fold, squeezing it so that the rubber cord is on top, as shown in the image.

Then, just turn on the device, follow the instructions in the device manual, and wait for the cuff to fill and empty again. The blood pressure value will be shown at the end of the process, on the device's screen.

Care when measuring blood pressure

Although measuring blood pressure is a relatively simple task, especially with the use of a digital sphygmomanometer, there are some precautions that must be respected to ensure a more reliable result. Some of these precautions include:

Avoid physical exercise, efforts or drink stimulating drinks, such as coffee or alcoholic beverages, in the 30 minutes prior to the measurement; Rest for 5 minutes before starting the measurement; Do not measure blood pressure in limbs that are being used to administer intravenous remedies, who have a shunt or arteriovenous fistula or who have suffered some type of trauma or malformation; avoid placing the cuff on the arm on the side of the breast or armpit undergoing any type of surgery.

Thus, when it is not possible to use an arm to measure blood pressure, a leg can be used, for example, by placing the cuff in the middle of the thigh, above the wrist that can be felt in the region behind the knee.

See also the normal blood pressure values and when it is recommended to measure the pressure.