Generality
The sphygmomanometer is the instrument through which it is possible to determine the arterial blood pressure .
Arterial pressure is a very important vital parameter, since its alterations - in defect or in excess - can give rise, or be an index, to very serious disorders.
The invention of the first sphygmomanometer models dates back to the second half of the nineteenth century, but it was only at the end of the same century that the Italian doctor Scipione Riva-Rocci invented the first mercury sphygmomanometer, still used today.
Currently, there are many types of sphygmomanometer on the market, which can be freely purchased and used by anyone. However, it is important to point out that the use of such an instrument must be carried out following some important rules in order to avoid measurement errors.
Curiosity
The word "sphygmomanometer" derives from the union of the Greek word sphygmòs (ie, impulse) with the union of the word manometer (that is, an instrument used to measure the pressure of a fluid).
What is that
What is the Sphygmomanometer and What is it for?
The sphygmomanometer is the instrument that is used - at both medical and domestic level - for the measurement of arterial blood pressure .
Thanks to this instrument, it is possible to obtain the values of both systolic and diastolic pressure . Blood pressure is an extremely important vital parameter which, especially in those at risk, must be kept under control in order to promptly identify the presence of potentially dangerous conditions for the patient's life.
Short Review: Normal Values for Blood Pressure
Before going into the description of the different types of sphygmomanometer and how to use them, let's remember what are the blood pressure values that a healthy person should have:
- Systolic pressure (or maximum pressure): 115-120 mmHg
- Diastolic pressure (or minimum pressure): 75-80 mmHg
In some cases, normal systolic pressure values up to 140 mmHg and diastolic pressure values up to 90 mmHg can be considered, however, if you find yourself in this situation it is still good to inform your doctor promptly.
For more information, read also: Pressor values.
Types
Types of Sphygmomanometer
As mentioned, different types of sphygmomanometer can be found on the market, which, however, can be classified into two large groups based on the mode of operation. More in detail, it is possible to distinguish between manual and analogue sphygmomanometers from electronic sphygmomanometers that measure blood pressure automatically .
Did you know that ...
Given the origin of the name "sphygmomanometer" and given the different functioning of the electronic devices used for the determination of arterial pressure, to speak of "electronic sphygmomanometer" is not really correct. However, by extension - even if in an improper way - in common language it is not unusual to talk about electronic sphygmomanometers to indicate all those automatic pressure gauges whose operation is regulated by an electronic unit.
Generally, electronic sphygmomanometers can also be used by less experienced people and, for this reason, they are the tools most used for constant pressure control at the domestic level.
However, the main characteristics of the different types of sphygmomanometer will be analyzed in more detail below, the method of use will be briefly described and the main advantages and disadvantages will be listed.
Manual sphygmomanometer
Features of the Manual Sphygmomanometer
The manual sphygmomanometer is a tool whose use is entirely manual and does not include any type of electronic component. The manual sphygmomanometer is commonly used in clinical and hospital settings, or in any case by health personnel. However, if you have the necessary knowledge, it can also be used at home; otherwise, it is better to use fully automated tools. In fact, in order to perform the measurement of systolic and diastolic blood pressure with the manual sphygmomanometer - as will be seen below - it is necessary to know how to use the phonendoscope (or stethoscope, if you prefer).
Mercury sphygmomanometer
The mercury sphygmomanometer can be considered as the forefather of the most modern manual sphygmomanometers.
To be fair, this instrument is still used today, although its use is not recommended due to the toxicity of mercury and the difficulty involved in its disposal.
The mercury sphygmomanometer is composed of a cloth sleeve that covers an air chamber connected to a pump equipped with a metal valve and to the characteristic mercury column . Next to it, there is a graduated scale that shows the different blood pressure values expressed in millimeters of mercury (mmHg). The reading of this scale occurs in the same way as reading the scale of the classic mercury thermometer used to measure body temperature.
Did you know that ...
The mercury sphygmomanometer is considered by many to be the most accurate instrument for measuring blood pressure.
Aneroid sphygmomanometer
The aneroid sphygmomanometer is a type of mercury-free manual blood pressure monitor . It is also equipped with a sleeve consisting of an air chamber that must be inflated using the appropriate pump - fitted with a metal valve - connected to it.
Instead of the mercury column, however, the aneroid sphygmomanometer has a clock gauge with a mobile needle . The latter has a graduated scale in millimeters of mercury (mmHg) and is connected by rubber tubes to the pump used for inflating the sleeve.
Mode of use
Blood pressure measurement with a manual sphygmomanometer can be performed using two different methods:
- Palpatory method : it uses only the manual sphygmomanometer but allows the measurement of the systolic pressure only . It will not be taken into consideration in this article.
- Auscultatory method : involves the use of both the sphygmomanometer and the phonendoscope and allows the detection of both systolic and diastolic pressure . It is the method that will be taken into consideration in this article.
Please note
Below is a brief description of how to use the manual sphygmomanometer. For more detailed information on the measures to be taken to take a correct blood pressure measurement, we recommend reading the dedicated article: How is Pressure Measured?
The use of the manual sphygmomanometer can be summarized in the following phases:
- Insert the sleeve into the arm and fasten it at the biceps, so to speak, above the elbow from which it is necessary to be a few centimeters apart. The sleeve must be of a size appropriate to the circumference of the patient's arm in order to avoid measurement errors (on the market there are different types of sleeves that cover various ranges of circumference). Furthermore, remember that the sleeve must not be too tight (generally, a space of about one finger is left between the sleeve and the arm).
Please note
To perform a correct pressure measurement, the arm must be at the same height as the heart . This explains why the pressure should always be tested in a sitting position by resting the forearm on a flat surface (such as a table).
- Once the sleeve has been placed, it is necessary to position the stethoscope bell just below it, in correspondence with the fold of the arm, to be able to perceive the noises coming from the brachial artery . Of course, before proceeding with the measurement it is necessary to place the earplugs of the phonendoscope in the ears.
- Using the pump, the cuff is inflated and must continue until no more pulse is felt at the brachial artery, a sign that the blood flow has been interrupted by the pressure exerted by the swollen cuff. When no more pulse is felt, some advise further increasing the sleeve pressure by another 20 mmHg.
- After that, the sleeve must be slowly deflated using the appropriate valve on the pump. During this operation, at some point you will feel a sort of snap, a sign of the resumption of blood flow . When the noise in question is heard, it is necessary to read the pressure value on the graduated scale of the sphygmomanometer, thus determining the systolic or maximum pressure . As the deflation progresses, the perceived noise will take on the rhythm of the heartbeat and decrease until it disappears completely . At this point, it is necessary to check the graduated scale again, thus determining the value of diastolic or minimum pressure .
Did you know that ...
The noises that are perceived with the phonendoscope during deflation of the sphygmomanometer sleeve are called Korotkoff sounds or tones .
Care of the Manual Sphygmomanometer
The manual sphygmomanometer usually requires periodic calibrations to ensure correct measurements are taken. To do this, it is necessary to contact industry specialists, the manufacturer or request information from the retailer where the instrument was purchased.
As for cleaning, some types of sleeves can be cleaned with water and a mild detergent, while the pressure gauge should only be cleaned with a dry cloth. However, it is always a good idea to refer to the information on the packaging or the user manual.
When not in use, the manual sphygmomanometer must be stored in its case in a safe place where it is not subject to knocks and where there is no risk of falling.
Advantages and disadvantages
The main advantage of the manual sphygmomanometer lies in its high precision (especially with regard to the mercury sphygmomanometer) which, however, turns out to be such only if the instrument is used correctly. This great advantage is, therefore, connected to the greatest disadvantages of the instrument in question, namely the difficult use and the need to have sufficient knowledge of the manual method of pressure measurement. In fact, remember that - in order to determine both systolic and diastolic pressure - the use of a phonendoscope is essential. It follows that the operator must necessarily be able to distinguish and interpret the sounds of Korotkoff .
Therefore, although the manual sphygmomanometer can be freely purchased in specialized shops as well as online, if you do not have the necessary knowledge for its use, it is advisable to avoid using it.
Electronic sphygmomanometer
Characteristics of the Electronic Sphygmomanometer
The electronic sphygmomanometer is a pressure meter that determines the systolic and diastolic pressure electronically.
The instrument in question is equipped with a sleeve consisting of an air chamber which, through a rubber tube, is connected to an electronic device . The electronic device in question is able to inflate and deflate the sleeve and - through a special sensor capable of detecting pressure variations - it collects and processes the data, then showing the pressure values on a digital screen.
Mode of use
The use of electronic sphygmomanometers is much simpler than using manual instruments.
In these cases, in fact, after having connected the sleeve in the correct position on the arm, it is sufficient to press the dedicated button to operate the instrument. The electronic device will then inflate the sleeve and then deflate it slowly, collecting the data and showing the measurement results on the display.
Please note
Also in this case, to make a correct measurement it is necessary that the arm is at the same height as the heart .
Care of the Electronic Sphygmomanometer
The instrument must be kept in its case in a safe place where there is no risk of being knocked or dropped. At the same time, it is advisable to keep the sphygmomanometer in a cool, dry place in order to avoid damage to the electronic components.
If the instrument should not be used for long periods of time, if possible, it is advisable to remove the batteries from their housing.
Finally, remember that, approximately every six months, it is a good idea to have the instrument checked and recalibrated in order to correct any tearing that inevitably occurs over time. To do this, it is possible, for example, to go to shops that deal with the sale of health merchandise or to request information directly from the seller of the appliance.
Advantages and disadvantages
The main advantages of the electronic sphygmomanometer consist substantially in:
- Simplicity of use;
- Measurement speed;
- Possibility of using the instrument even by inexperienced individuals since no particular knowledge is required;
- Reduction of errors caused by the observer (reading errors, rounding, etc.);
- Possibility of providing other information, such as heart rate;
- Possibility of possessing additional functions (for example, the alarm clock to remember to carry out the measurement every day at the same time, the memory function to keep track of past pressure values, etc.).
The disadvantages, instead, consist substantially in the cost - decidedly high for the most complex and advanced instruments - and in the measurement precision which can be lower than the determination of the pressure values by manual sphygmomanometer (provided that the latter is used by specialized personnel).
Electronic Wrist Sphygmomanometer
The electronic wrist sphygmomanometer can be considered as a sort of simpler variant to use than the common electronic sphygmomanometer equipped with a sleeve.
Sphygmomanometers of this type measure arterial pressure on the wrist and have met with considerable success in the field of pressure measurement at the domestic level. However, compared to the electronic sphygmomanometers with a sleeve, the wrist ones have noteworthy disadvantages such as:
- Possibility to make mistakes due to the hydrostatic differential pressure between arm and heart . In this case too, in fact, to avoid incorrect measurements, the pulse should be at the level of the heart.
- Possibility of measurement errors due to wrist movements - even involuntary - carried out while the instrument is in operation.
Therefore, due to the aforementioned disadvantages, it is advisable to prefer a sphygmomanometer that measures blood pressure in the arm rather than the wrist.
