Sphygmomanometer - Types, Parts, How To Use, FAQs

Edited By Vishal kumar | Updated on Jul 02, 2025 05:02 PM IST

Introduction

The force applied by the blood on the wall of the blood vessels is named as the blood pressure. Sphygmomanometer is used to measure blood pressure. In this article we will learn in detail about the sphygmomanometer, sphygmomanometer parts (also bp apparatus parts) sphygmomanometer uses and sphygmomanometer types: mercury sphygmomanometer, aneroid sphygmomanometer and digital sphygmomanometer.

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Introduction
What is a sphygmomanometer?
Types of sphygmomanometer:
How to check blood pressure using sphygmomanometer?

Sphygmomanometer - Types, Parts, How To Use, FAQs

What do we know about blood pressure?

The pressure is higher in arteries than the veins. High blood pressure is also called hypertension. All blood applies a thrust on the muscular walls of the blood vessels. That thrust is said to be as blood pressure and it increases and decreases with the beating of the heart. It's highest during systole, when the heartbeat contracts to force blood through the arteries. This is your systolic blood pressure. When the heart is at relaxation in the middle of beats blood pressure drops to its lowest value, the diastolic pressure. A typical healthy individual produces a systolic pressure between 90 and 120 mm of mercury and diastolic pressure between 60 and 80 mm of mercury. Taking together a normal reading is a bit less than 120 over 80. The blood traverses the landscapes of the body through the pipes of the circulatory system. In any plumbing system several things can Increase the force on the wall of the pipes: The properties of the fluid, extra fluid or narrower pipes. So if the blood coagulates a higher pressure is required to push it therefore the heart will pump harder. A high salt intake will lead to alike result. The salt promotes water retention and the extra fluid increases the blood volume and blood pressure and stress like the fight or flight response releases hormones like epinephrine or norepinephrine that compress key vessels, increasing the struggle to flow and raising the pressure upstream. Blood vessels can generally lever these fluctuations with ease. Elastic fibres embedded in their walls make them resilient but if your blood pressure regularly rises above about 140 over 90 what we call hypertension and stays there. It can cause serious problems.

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What is a sphygmomanometer?

Sphygmomanometer measures the blood pressure of a person. Who invented sphygmomanometer? Sphygmomanometer invented by Von Basch. It is a instrument that is in every household nowadays. Sphygmomanometer cost is between 1000 to 2000 rupees. Sphygmomanometer in Hindi is रक्तदाबमापी

Now let us answer to the question what are sphygmomanometer parts name? How to measure blood pressure with sphygmomanometer? How to use sphygmomanometer?

Types of sphygmomanometer:

There are three types of sphygmomanometer: mercury sphygmomanometer, aneroid sphygmomanometer and digital sphygmomanometer.

Mercury sphygmomanometer: This is utmost conformist type of blood pressure tool and is well-thought-out to be the golden standard. This apparatus contain manually inflated cuffs which are connected to the mercury infused tunes for attaining the accurate measurement or readings. The apparatus must be kept on a plane surface and in vertical position. In case if the apparatus is dropped accidentally then there are enhanced possibilities of risks.

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This is utmost conformist type of blood pressure tool and is well-thought-out to be the golden standard.

Mercury bp apparatus price in India is between 1000 to 2000 rupees. Advantages: last for life time, easy to use and no need of recalibration. Disadvantages: because of its toxic content it is banned in some nations.

Aneroid sphygmomanometer:

aneroid meaning is without fluid.

Aneroid sphygmomanometer meaning is without fluid. Mercury is not used in this type of sphygmomanometer. This contain a stethoscope that is connected to the cuff which is further connected to a dial gauge with tubing. To cover the cuff pressure to gauge pressure the gauge head have a mechanical portion. This apparatus required to be recalibrated to avoid false readings. There are other various kinds of aneroid sphygmomanometer based on their usage.

Digital sphygmomanometer:

This is the most technologically advanced sphygmomanometer. This contain an electronic sensor to measure the blood pressure and the measurement are shown on the digital monitor.

it is the most technologically advanced.

To measure the blood pressure the apparatus measure the fluctuations of arteries. These require to be checked using mercury sphygmomanometer to avoid inaccurate readings.

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Parts of sphygmomanometer

An inflated flat rubber bag covered by a non distensible cloth envelope. The cavity of the bag is connected by a long rubber tube to a Manometer and by a short tube to a rubber pump. By this way the bag can be overblown to any anticipated pressure. A small valve is provided between the pump and the bag which permits the escape of air and reduction of the pressure as required to compensate tissue resistance. The Manometer is a U shaped tube, one limb being extensive than another. The broader limb is the reservoir for mercury and the narrow limb is graduated from 0 to 300 mm with the smallest division corresponding to a reading of 2mm hg. The inflated bag dimensions for adults are 23*12.5 cm, width of these bag varies with the age of the individual: below 1 year- 2.5 cm, below 4 years- 5 cm, below 8 years- 8 cm and for adults- 12.5 cm. Sphygmomanometer working principle: It involves the balancing of pressure in a bag that is air pressure against the pressure of the blood in an artery. This air pressure is estimated by means of mercury or air Manometer.

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How to check blood pressure using sphygmomanometer?

Two methods are commonly in use for the measurement of systematic arterial BP:

Palpatory method :

Allow the person to sit at ease in a chair or to lie horizontal on the check-up couch for 5 minutes. The uninflated cuff of sphygmomanometer is wrapped firmly around the bare upper arm 2.5-3 cm above elbow joint at the heart level. Feel for the radial pulse ND inflate the rubber bag to increase the pressure 20-30 mm Hg above the points at which the radial pulse will disappear at the wrist. Now deflate the cuff slowly releasing the pressure at the rate of 2-3 mm Hg/sec. While lowering the pressure keep palpating the radial artery and reading is taken just when pulse start reappearing. This gives the systolic BP. Disadvantages of this method are that diastolic BP cannot be estimated and systolic BP estimated is lower than the actual by 6-10 mm hg.

Auscultatory method:

Allow the person to sit at ease in a chair or to lie horizontal on the check-up couch for 5 minutes. The uninflated cuff of sphygmomanometer is wrapped firmly around the upper area 2.5-3 cm above the elbow joint at the heart level. Place the chart piece on stethoscope over the arm medial to the tendon of biceps where the pulsations of brachial artery are felt. Under ordinary circumstances if a stethoscope is placed over an artery no sound can be heard, as the stream line flow of blood through the unconstructed blood vessels produces no sound. Inflate the cuff rapidly until the pressure in it is well above the systolic BP as measured by the palpatory method. The brachial artery gets occluded by the cuff and no sound can be heard with the stethoscope. Now gradually lower the cuff pressure by opening the valve till a clear sharp tapping sound is heard. The cuff pressure at which the sound is heard first, gives a measure of systolic BP. The pressure in the cuff is further progressively lowered while listening for the appearance of the sound of Korotkoff's. The sound undergoes a series of changes in quality and becomes dull and muffled to disappear finally. The cuffs pressure at which the sound becomes muffled or disappears is the diastolic BP.

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Frequently Asked Questions (FAQs)

1. What are bp instrument all parts name?

Bp instruments part name are: pressure cuff, bulb, pressure control valve and a tube.

2. Who discovered the sphygmomanometer?

Sphygmomanometer was discovered by Von Basch.

3. Write one precaution while using a sphygmomanometer?

Cuff should be placed at the level of the heart while taking readings.

4. How many methods are there to measure bp?

There are two methods:Palpatory method and Auscultatory method.

5. Name types of sphygmomanometer.

Mercury sphygmomanometer, Aneroid sphygmomanometer and Digital sphygmomanometer.

6. How does a sphygmomanometer work based on fluid mechanics principles?

A sphygmomanometer works on the principle of hydrostatic pressure. When the cuff is inflated, it applies external pressure to the artery, temporarily stopping blood flow. As the pressure is slowly released, blood begins to flow again, creating vibrations (Korotkoff sounds) that can be detected. The pressure at which these sounds appear and disappear corresponds to systolic and diastolic blood pressure, respectively.

7. What are the key components of a typical sphygmomanometer?

The key components of a typical sphygmomanometer include:

8. How does the cuff size affect blood pressure measurements?

Cuff size is crucial for accurate measurements. A cuff that's too small will overestimate blood pressure, while one that's too large will underestimate it. The bladder inside the cuff should encircle about 80% of the arm's circumference. Using the wrong cuff size can lead to misdiagnosis and improper treatment of hypertension or hypotension.

9. What is the auscultatory method in blood pressure measurement?

The auscultatory method involves listening for Korotkoff sounds using a stethoscope while slowly deflating the cuff. The pressure at which the sounds first appear is recorded as the systolic pressure, and the pressure at which they disappear is the diastolic pressure. This method requires skill and practice to perform accurately.

10. How does gravity affect blood pressure measurements?

Gravity significantly affects blood pressure measurements. The hydrostatic pressure in a column of fluid (like blood in vessels) changes with height. For accurate readings, the arm should be at the same level as the heart. If the arm is below heart level, the reading will be artificially high; if above, it will be artificially low.

11. What is white coat hypertension and how does it affect measurements?

White coat hypertension is a phenomenon where a patient's blood pressure is higher in a clinical setting than in other environments. It's caused by anxiety or stress related to the medical environment. This can lead to overdiagnosis of hypertension if not accounted for, highlighting the importance of multiple measurements and home monitoring.

12. What is the difference between ambulatory and clinic blood pressure measurements?

Ambulatory blood pressure monitoring (ABPM) involves wearing a portable device that takes measurements over 24 hours during normal daily activities. Clinic measurements are one-time readings taken in a healthcare setting. ABPM provides a more comprehensive picture of blood pressure variations and can help identify phenomena like white coat hypertension or masked hypertension.

13. What is the importance of regular calibration for sphygmomanometers?

Regular calibration is crucial for maintaining the accuracy of sphygmomanometers. Aneroid devices, in particular, can lose accuracy over time due to mechanical wear. Mercury devices are more stable but still require checks. Digital devices have internal calibration but should be checked against a known standard periodically. Inaccurate devices can lead to misdiagnosis and improper treatment of hypertension or hypotension.

14. How does the principle of Bernoulli's equation relate to blood pressure measurement?

Bernoulli's equation in fluid dynamics relates pressure, velocity, and elevation in a flowing fluid. In blood vessels, as the cross-sectional area narrows, blood velocity increases, and pressure decreases. This principle is relevant in understanding how arterial constriction or dilation can affect local blood pressure and flow, which in turn influences the measurements obtained by a sphygmomanometer.

15. How does arterial compliance affect blood pressure readings?

Arterial compliance, or the ability of arteries to expand and contract with pressure changes, affects blood pressure readings. Less compliant (stiffer) arteries, often seen in older individuals or those with certain cardiovascular conditions, can lead to higher systolic pressure readings. This is because stiffer arteries require more pressure to expand during the heart's contraction.

16. What are the main types of sphygmomanometers?

The main types of sphygmomanometers are:

17. Why were mercury sphygmomanometers considered the gold standard?

Mercury sphygmomanometers were considered the gold standard because mercury's high density and low compressibility make it excellent for precise pressure measurements. The height of the mercury column directly corresponds to the pressure applied, providing accurate and consistent readings. However, due to environmental concerns about mercury, they are being phased out in many places.

18. How does an aneroid sphygmomanometer differ from a mercury one?

An aneroid sphygmomanometer uses a mechanical system with a metal bellows and spring mechanism instead of a mercury column. When pressure is applied, the bellows expand, moving a series of levers that rotate a needle on a calibrated dial. While more portable and mercury-free, aneroid devices require more frequent calibration to maintain accuracy.

19. How do digital sphygmomanometers work?

Digital sphygmomanometers use oscillometric measurements. They detect vibrations in the arterial wall as blood begins to flow after cuff deflation. These devices use algorithms to calculate systolic and diastolic pressures based on the pattern of oscillations. They're easier to use but may be less accurate in certain conditions like arrhythmias.

20. How do changes in atmospheric pressure affect sphygmomanometer readings?

Changes in atmospheric pressure have minimal direct effect on sphygmomanometer readings because the device measures relative pressure (the difference between cuff pressure and atmospheric pressure). However, extreme changes in altitude or atmospheric conditions can affect the calibration of aneroid devices, necessitating recalibration.

21. What is a sphygmomanometer?

A sphygmomanometer is a medical device used to measure blood pressure. It consists of an inflatable cuff to restrict blood flow, a measuring unit to read the pressure, and a mechanism to gradually release the pressure. The name comes from the Greek words "sphygmos" (pulse) and "manometer" (pressure meter).

22. How does the principle of Pascal's law apply to blood pressure measurement?

Pascal's law states that pressure applied to an enclosed fluid is transmitted equally in all directions. In a sphygmomanometer, this principle ensures that the pressure applied by the cuff is transmitted uniformly through the tissues to compress the artery, allowing for accurate measurement of the pressure required to occlude and release blood flow.

23. What is the difference between systolic and diastolic pressure?

Systolic pressure is the pressure in the arteries when the heart contracts (beats), pushing blood into the arteries. Diastolic pressure is the pressure in the arteries when the heart is relaxed between beats. They represent the maximum and minimum pressures in the arterial system during a cardiac cycle.

24. How does arterial stiffness affect blood pressure measurements?

Arterial stiffness, often associated with aging or certain diseases, can affect blood pressure measurements. Stiffer arteries require more pressure to compress, potentially leading to higher systolic readings. Additionally, the oscillations detected by automated devices may be altered, affecting their accuracy. This is one reason why manual measurements may be preferred in older patients or those with certain cardiovascular conditions.

25. What is the "null" method in sphygmomanometry?

The null method is an alternative technique for measuring blood pressure, particularly useful in noisy environments. Instead of listening for Korotkoff sounds, the observer watches for the cessation and reappearance of oscillations in the mercury column or aneroid gauge needle as the cuff is inflated and deflated. This method can be more reliable in situations where auscultation is difficult.

26. How does respiratory variation affect blood pressure measurements?

Respiration can cause cyclical variations in blood pressure. During inspiration, intrathoracic pressure decreases, increasing venous return and right heart filling, which can temporarily decrease left ventricular stroke volume and arterial pressure. This effect is more pronounced in some conditions like pericardial effusion. To minimize this effect, measurements are often taken at the end of expiration.

27. Why is it important to rest before taking a blood pressure measurement?

Resting before measurement is crucial because physical activity, stress, and anxiety can temporarily elevate blood pressure. A rest period of 3-5 minutes allows the cardiovascular system to return to its baseline state, ensuring a more accurate representation of the patient's typical blood pressure.

28. What is the importance of the stethoscope's placement in manual blood pressure measurement?

The stethoscope should be placed over the brachial artery, usually in the antecubital fossa (inner elbow). Correct placement is crucial for hearing the Korotkoff sounds clearly. Improper placement can lead to missed or muffled sounds, resulting in inaccurate readings.

29. How does arm circumference affect the choice of cuff size?

Arm circumference directly determines the appropriate cuff size. A cuff that's too narrow for a large arm will require more pressure to occlude the artery, leading to falsely high readings. Conversely, a cuff that's too wide for a small arm will occlude the artery at lower pressures, resulting in falsely low readings. Most adults require a cuff with a bladder length that is 80% of the arm circumference and a width that is 40% of the arm circumference.

30. What is the "auscultatory gap" and why is it important?

The auscultatory gap is a phenomenon where Korotkoff sounds temporarily disappear between the systolic and diastolic pressure points. It's important because it can lead to underestimation of systolic pressure or overestimation of diastolic pressure if not recognized. To avoid this, the cuff should be inflated to a higher pressure and deflated slowly while listening carefully.

31. What is the importance of the deflation rate in manual blood pressure measurement?

The deflation rate is crucial for accurate measurements. The recommended rate is 2-3 mmHg per second. If the cuff is deflated too quickly, it can lead to underestimation of systolic pressure and overestimation of diastolic pressure. Deflating too slowly can cause discomfort and potential venous congestion, affecting the reading.

32. How do caffeine and nicotine affect blood pressure measurements?

Both caffeine and nicotine can cause short-term increases in blood pressure. Caffeine can raise systolic pressure by 3-14 mmHg and diastolic by 4-13 mmHg, while nicotine can cause an immediate spike in both. For accurate readings, it's recommended to avoid these substances for at least 30 minutes before measurement.

33. How does temperature affect sphygmomanometer accuracy?

Temperature can affect sphygmomanometer accuracy, particularly in aneroid and digital devices. Extreme temperatures can alter the properties of the mechanical components in aneroid devices or affect the electronic components in digital ones. Most devices are calibrated for use at room temperature, and significant deviations can lead to inaccurate readings.

34. How does the position of the patient affect blood pressure readings?

Patient position significantly affects blood pressure readings. Generally, the supine (lying down) position results in the highest readings, followed by sitting, and then standing. These differences are due to the effects of gravity on blood distribution in the body. For consistency, it's recommended to take measurements in the same position, usually sitting, with the back supported and feet flat on the floor.

35. What is the importance of using the correct arm for blood pressure measurement?

Blood pressure should ideally be measured in both arms initially. A significant difference (usually >10 mmHg) between arms could indicate underlying vascular problems. After initial assessment, the arm with the higher pressure should be used for subsequent measurements. Using the correct arm ensures more accurate monitoring of blood pressure over time.

36. How do arrhythmias affect blood pressure measurements?

Arrhythmias can significantly complicate blood pressure measurements, especially with automated devices. Irregular heartbeats can cause variations in blood flow and pressure, making it difficult to determine accurate systolic and diastolic pressures. In patients with known arrhythmias, manual auscultation by a skilled practitioner is often preferred over automated methods.

37. What is the principle behind the oscillometric method used in digital sphygmomanometers?

The oscillometric method detects oscillations in cuff pressure as blood begins to flow through the artery during cuff deflation. The point of maximum oscillation corresponds roughly to the mean arterial pressure. Systolic and diastolic pressures are then calculated using algorithmic interpretations of the oscillation amplitude changes. This method allows for automated measurements without the need for a stethoscope.

38. How does cuff deflation speed affect digital sphygmomanometer accuracy?

In digital sphygmomanometers, cuff deflation speed is carefully controlled, usually at about 2-3 mmHg per second. This controlled rate allows the device to detect subtle changes in oscillations accurately. If the deflation is too fast, it may miss critical data points, while if it's too slow, it can cause discomfort and potentially affect the reading due to prolonged arterial occlusion.

39. What is the effect of cuff placement above or below the heart level?

Cuff placement relative to heart level is critical due to hydrostatic pressure effects. For every 10 cm above heart level, the reading will be approximately 7 mmHg lower than the true value. Conversely, for every 10 cm below heart level, the reading will be about 7 mmHg higher. This emphasizes the importance of proper arm positioning during measurement.

40. What is the significance of the fifth Korotkoff sound in blood pressure measurement?

The fifth Korotkoff sound, characterized by the disappearance of audible sounds, is generally used to determine diastolic blood pressure in adults. In some cases, particularly in children or pregnant women, the fourth Korotkoff sound (muffling of sounds) may be used instead. Understanding the difference is crucial for accurate diastolic pressure determination in various patient populations.

41. What is the concept of "cuff sphygmomanometry" and how does it differ from invasive methods?

Cuff sphygmomanometry refers to the non-invasive method of measuring blood pressure using an inflatable cuff. It estimates arterial pressure indirectly by observing the pressure required to occlude and release blood flow. In contrast, invasive methods involve direct measurement of pressure within the artery using a catheter. While invasive methods are more accurate, cuff sphygmomanometry is preferred for routine use due to its safety and convenience.

42. How does the choice of stethoscope (bell vs. diaphragm) affect blood pressure measurement?

The choice between the bell and diaphragm of a stethoscope can affect blood pressure measurement. The bell is more sensitive to low-frequency sounds and is generally preferred for detecting the low-pitched Korotkoff sounds, especially the diastolic endpoint. The diaphragm is better for higher-frequency sounds and may be used in noisy environments. However, with proper technique, either can be used effectively.

43. What is the importance of cuff bladder size in relation to limb circumference?

The cuff bladder size relative to limb circumference is crucial for accurate measurements. The bladder width should be about 40% of the limb circumference, and its length should encircle at least 80% of the limb. A bladder that's too narrow or short will overestimate blood pressure, while one that's too wide or long may underestimate it. This is why different cuff sizes are necessary for different patient populations.

44. How does the principle of laminar vs. turbulent flow apply to blood pressure measurement?

Blood flow is typically laminar in normal conditions. However, when the artery is partially occluded by the cuff, the flow becomes turbulent as it passes through the narrowed section. This turbulence creates the Korotkoff sounds heard during measurement. Understanding this transition from laminar to turbulent flow is key to interpreting the sounds heard during manual blood pressure measurement.

45. What is the effect of cuff wrapping technique on blood pressure readings?

The cuff wrapping technique can significantly affect readings. The cuff should be wrapped snugly but not too tightly, with the bladder centered over the artery. If the cuff is wrapped too loosely, it may require more pressure to occlude the artery, leading to falsely high readings. Conversely, if it's too tight, it may occlude the artery at lower pressures, resulting in falsely low readings.

46. How does the concept of mean arterial pressure (MAP) relate to systolic and diastolic measurements?

Mean