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How Do Blood Pressure Cuffs Work

Blood Pressure Cuff Too Big For Arm

How Does a Blood Pressure Cuff Work?

A blood pressure cuff too big for the arm will cut the blood flow faster resulting in a lower blood pressure measurement. What is the blood pressure cuff size rule?

It is recommended the blood pressure cuff bladder length should be 75-100% of the upper arm circumference. The width should be 37-50% of the upper arm circumference.

Its important to use a monitor with an arm circumference range fitting the upper arm. Lets say a monitor comes with a standard size cuff range between 8.75-16.5. If the arm measures 15, typically this size cuff and inside bladder would be appropriate for measuring blood pressure 4.

The cuff bladder is located inside the the blood pressure cuff material. The bladder is what fills up with air when the monitor is turned on. The air supply tube connects inside to the bladder and provides air from the monitor.

My article, Blood Pressure Cuff Too Large, contains three studies which informs you how much blood pressure was lower when using a cuff too large. In addition, it has tips on avoiding the problem.

What Are The Common Causes Of Getting Blood Pressure Readings That Are Inaccurate

It is quite normal for peoples blood pressure to change throughout the day and night, or in different settings where you may take your blood pressure. Many things, such as stress levels, food or drink intake, activity levels, even time of day can all affect a persons blood pressure reading at any given time. So, it is possible that you may just be seeing normal fluctuations in blood pressure.

However, below are some common situations that can lead to inconsistent or inaccurate readings:

Blood Pressure Without A Cuff

Pulse characteristics are an unreliable signand should be used only as a last resort.90 Without scientific evidence, the advanced trauma life support course taught that systolic BP can be estimated from whether radial , femoral , or carotid pulses are palpable. This method tends to overestimate the patient’s BP. Although the radial pulse always disappears before the femoral pulse, which always disappears before the carotid pulse, most patients’ actual BP is lower than that predicted by these guidelines. That information by itself could be useful in a crisis.22

Nonhypothermic patients with extremities that are cooler than normal may have hypoperfusion. If it is assessed in multiple extremities, especially in both an arm and a leg, checking a palpable temperature effectively diagnoses hypoperfusion. These patients have lower cardiac indexes, lower pH, lower bicarbonate levels, lower mixed venous oxygen saturation, and higher lactate levels.74 In a neonate, a cold or dusky sole of the foot can indicate hypothermia, hypoxemia, and/or hypotension.21

Donald J. Krapohl, Pamela K. Shaw, in, 2015

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Oscillatory Blood Pressure Monitoring Devices

Pressure against using mercury in clinical practice is coming from environmentalists, and, in line with other countries in Europe, mercury column devices for measuring blood pressure are likely to be stopped being manufactured soon in Britain.

Aneroid devices which also depend on auscultation are gaining popularity, as are devices which depend on oscillation. Oscillatory devices produce a digital readout and work on the principle that blood flowing through an artery between systolic and diastolic pressures causes vibrations in the arterial wall which can be detected and transduced into electrical signals.

With an oscillatory device, a cuff is inflated over the upper arm or wrist. The new models use fuzzy logic to decide how much the cuff should be inflated to reach a pressure about 20 mm Hg above systolic pressure for any individual. When the cuff is fully inflated to this pressure, no blood flow occurs through the artery. As the cuff is deflated below the systolic pressure, the reducing pressure exerted on the artery allows blood to flow through it and sets up a detectable vibration in the arterial wall. When the cuff pressure falls below the patient’s diastolic pressure, blood flows smoothly through the artery in the usual pulses, without any vibration being set up in the wall. Vibrations occur at any point where the cuff pressure is sufficiently high that the blood has to push the arterial wall open in order to flow through the artery.

BMJ Publishing Group

Why Do I Need A Blood Pressure Test

Do Wrist Blood Pressure Monitors Work As Well As Arm

A blood pressure measurement is often included as part of a regular checkup. Adults 18 years and older should have their blood pressure measured at least once every two to five years. You should get tested every year if you have certain risk factors. You may be at higher risk if you:

  • Are 40 years old or older
  • Are overweight or have obesity
  • Are Black/African American. Black/African Americans have a higher rate of high blood pressure than other racial and ethnic groups

You may need this test if you have symptoms of low blood pressure.

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Will I See Differences Between My Readings At Home Compared To Readings In My Doctor’s Office

Yes, you will see some differences. This is normal and can occur for many reasons. Some of the more common reasons are:

  • A persons blood pressure varies throughout the day, so at any given moment your blood pressure can change.
  • In terms of the amount of change there are published studies that show a given persons blood pressure can change by up to 20 mm within a day, based on activity levels, food/drink intake, stress, etc.
  • You may have a condition known as White Coat Hypertension. This is a condition in which a blood persons blood pressure rises above its usual level when it is measured in a doctors office or clinical setting.
  • You may have a condition known as Masked Hypertension. This is a situation in which a persons blood pressure falls below its usual level when it measure in a doctors office or clinical setting.
  • So do not be alarmed when you see differences between your readings at home compared to your readings in your doctors office. Discuss it with your doctor to get the best overall picture of your heart health.

    How To Check Your Blood Pressure At Home

    To get a precise reading

    • Dont drink caffeinated beverages, exercise, or smoke for at least 30 minutes before taking your blood pressure.
    • Go to the bathroom and take at least 5 minutes to relax before taking the test.5
    • Sit with a straight and supported back, with both of your feet on the floor. Your upper arm should be at heart level and supported on a flat surface like a table. The bottom of the cuff should be directly above the elbow bend.5
    • Measurements should be taken at the same time every day. It is recommended to take your blood pressure readings every day, or as requested by your doctor.5
    • You should avoid taking your blood pressure measurements over clothing, or when wearing tight clothes.5

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    What Do The Results Mean

    Your results, also known as a blood pressure reading, will contain two numbers. The top or first number is the systolic pressure. The bottom or second number is the diastolic pressure. High blood pressure readings are also labeled by categories, ranging from normal to crisis. Your reading may show your blood pressure is:

    Blood Pressure Category
    and 120 or higher

    If you’ve been diagnosed with high blood pressure, your provider may recommend lifestyle changes and/or medicines to control your blood pressure. Your provider may also recommend that you regularly check your blood pressure at home with an automated blood pressure monitor. An at-home blood pressure monitor usually includes a blood pressure cuff and a digital device to record and display blood pressure readings.

    Home monitoring is not a replacement for regular visits to your provider. But it can provide important information, such as whether treatment is working or your condition may have worsened. Also, home monitoring may make the test less stressful. Many people get nervous about getting their blood pressure taken at a provider’s office. This is called “white coat syndrome.” It can cause a temporary rise in blood pressure, making the results less accurate. For more information about home monitoring of blood pressure, talk to your provider.

    What Is The Difference Between The Comfit Cuff And The D

    How blood pressure monitors work?

    The ComFit cuff is pre-formed to wrap easily around your upper arm. It features 360º around the circumference of your arm to help reduce measurement errors and ensure inflation over your brachial artery. The D-Ring cuff is a soft contoured cuff that is designed for more comfortable measurement. This style is typically seen in a doctors office. You loop one end of the cuff through the D-shaped metal ring, put your arm through the cuff and then fasten the end around the arm. Both cuffs fit a standard- to large-sized adult arm. 9 to 17 in circumference.

    When purchasing an at-home blood pressure monitor, it is important to know your proper cuff size. To determine your arm size, use a cloth measuring tape and measure the circumference of your left upper arm midway between your elbow and shoulder. The blood pressure cuff must be neither too tight nor too loose to help ensure accurate readings, providing you with an accurate picture of your hearts health.

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    Auscultatory Measurement Of Blood Pressure

    The time-honoured, traditional measurement of BP uses an inflatable cuff encircling a limb combined with a stethoscope to detect sounds made by the flow of blood as it comes under the cuff . The cuff is inflated to a point where the pressure it exerts on the underlying arm is high enough to stop blood flowing underneath so that no blood flow sounds can be heard. As the cuff pressure is deflated the pressure transmitted from the cuff to the walls of the underlying arteries reduces to the point at which blood flow resumes and sounds begin to be heard. These sounds vary in intensity and usually stop at the point of the lowest pressure within the arteries before the next pulse arrives. The initial sound approximates to the peak and the final sound to the relaxation pressure in the artery . Listening to these sounds and interpreting them requires training and can be difficult especially if hearing is impaired or there is significant environmental noise.

    Are There Other Uses For 24

    Ambulatory blood pressure monitoring is increasingly being used to determine how well some antihypertensive drugs can control high BP. In some cases, antihypertensive drugs dont control BP effectively throughout the entire day and night. A doctor may need to adjust the dosage prescribed or the time that the medication is given, depending on the patients BP patterns. In other cases, more than one drug may be required to stabilize BP.

    Ambulatory BP monitoring can also help to predict the likelihood of cardiovascular and cerebrovascular disease linked to hypertension and organ damage.

    Ambulatory BP monitoring may also be suitable in other situations, such as for:

    • Pregnant women with hypertension.
    • Difficulty controlling BP with medication.
    • BP changes due to other drugs.
    • Changes in prescription medications that may impact BP.
    • Fainting episodes or hypotension .

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    Tips For Monitoring Your Blood Pressure Monitor Accuracy

    It is necessary to have your doctor check the accuracy of your home blood pressure monitors immediately after purchase. You should also take the monitor for accuracy check once a year. Ask your nurse or doctor to direct you on how to correctly use your blood pressure monitor. This will assist you in achieving a better result in managing your blood pressure.

    Other tips include

    • Measure your blood pressure 2 times daily

    You should take the first measurement in the morning before breakfast or taking any drugs, and the second measurement in the evening. Anytime you take the measurement, take up to 2 or 3 readings to ensure accurate results.

    • Do not take your blood pressure measurement immediately after waking up

    Take your blood pressure measurement before breakfast but not immediately after you wake up. If you do morning exercise, you must measure before exercising.

    • Take the necessary procedures

    Sit quietly and comfortably before and during the measurement. Make sure that your arm is positioned correctly. Place the cuff on your skin, not on the clothing, and make sure you avoid food, alcohol, caffeine, and tobacco products for at least 30 minutes before taking the measurement.

    • Repeat the reading

    Wait for 2 to 3 minutes after taking the first reading, then another one to ensure accuracy. If the monitor does not log blood pressure readings automatically, you should write them down.

    Tip: There are garlic pills which can help you lower blood pressure too.

    Can I Take A Blood Pressure Reading Measurement During Exercise

    How Blood Pressure Works Animation

    Omron blood pressure monitors are NOT intended for use during exercise or activity. We recommend that you avoid eating, drinking alcohol or caffeinated beverages, smoking, bathing and exercising for at least 30 minutes before taking a measurement. It is also best to rest for 15 minutes before starting the measurement.

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    How Much Does A Blood Pressure Monitor Cost

    Home blood pressure monitors cost somewhere between $29 and $370. While there are plenty of more expensive monitors available, there’s no real reason to pay more for home use and more expensive monitors may start to be targeted towards professional use.

    While this sounds good, in practice they may actually be harder to use, as their cuffs may not be designed to be put on by yourself. The important thing is to find one which is accurate, and which you’re comfortable using. See our blood pressure monitor reviews for more information.

    Omron Bp Cuff Sizes And Their Monitors

    1. Omron 10 Series Home Blood Pressure Monitor

    The blood pressure cuff that comes with the Omron 10 Series:

    • Pre-formed Easy-Wrap Comfit Cuff: Fits upper arms 9 to 17 in circumference

    Other blood pressure cuff sizes compatible with the Omron 10 Series:

    • None

    2. Omron Platinum Home Blood Pressure Monitor

    The blood pressure cuff that comes with the Omron Platinum:

    • Wide Range Cuff: Fits upper arms 9 to 17 in circumference

    Other blood pressure cuff sizes compatible with the Omron Platinum:

    • Small Cuff: Fits upper arms 7 to 9 in circumference

    3. Omron Gold Home Blood Pressure Monitor

    The Blood Pressure Cuff that comes with the Omron Gold:

    • Wide Range Cuff: Fits upper arms 9 to 17 in circumference

    Other blood pressure cuff sizes compatible with the Omron Gold:

    • Small Cuff: Fits upper arms 7 to 9 in circumference

    4. Omron 7 Series Home Blood Pressure Monitor

    The blood pressure cuff that comes with the Omron 7 Series:

    • Pre-formed Easy-Wrap Comfit Cuff: Fits upper arms 9 to 17 in circumference

    Other blood pressure cuff sizes compatible with the Omron 7 Series:

    • None

    Theres seven more Omron home monitors available, check out all the blood pressure cuff sizes included with them in this article I wrote recently, Omron Home Blood Pressure Cuff Sizes.

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    Is It Normal For My Blood Pressure To Vary

    Yes, it is quite normal for peoples blood pressure to change throughout the day and night, or in different settings where you may measure your blood pressure. Many things, such as stress levels, food or drink intake, activity levels, even time of day can all affect a persons blood pressure reading at any given time. In fact, there are published studies that show a given persons blood pressure can change by up to 20mm within a day, based on activity levels, food/drink intake, stress, etc. This is why it is important to take your blood pressure on a regular basis, and review the overall trend of your blood pressure readings with your doctor.

    For a convenient tool to help you easily track your blood pressure readings, click here.

    How Does A Blood Pressure Monitor Work

    How does a bloodpressure monitor work?

    Blood pressure is measured using a sphygmomanometer, or blood pressure monitor. It consists of an inflatable cuff thats wrapped around your arm, roughly level with your heart, and a monitoring device that measures the cuffs pressure.

    The monitor measures two pressures: systolic, and diastolic. Systolic pressure is higher, occurring when your heart beats and pushes blood through the arteries, and diastolic pressure is measured when your heart is resting and filling with blood. So, for example, your blood pressure might be 120 over 80.

    Blood pressure monitors may be manual or digital, but home monitors are usually digital and the whole measurement process is automatic apart from placing the cuff around your arm.

    The cuff then inflates until it fits tightly around your arm, cutting off your blood flow, and then the valve opens to deflate it. As the cuff reaches your systolic pressure, blood begins to flow around your artery. This creates a vibration thats detected by the meter, which records your systolic pressure. In a traditional analogue sphygmomanometer, the blood sounds are detected by the doctor using a stethoscope.

    As the cuff continues to deflate, it reaches your diastolic pressure, and the vibration stops. The meter senses this, and records the pressure again.

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    What If I Don’t Have High Or Low Blood Pressure

    High blood pressure is one symptom of preeclampsia, a condition that affects 5% to 8% of pregnancies.

    People who are otherwise healthy but at an increased risk of developing hypertension and cardiovascular disease, such as people with a family history of early hypertension or women with a history of preeclampsia during pregnancy, can also benefit from SMBP tests. “Monitoring home blood pressure from time to time can provide an early window into elevated blood pressures, giving higher-risk people the feedback they need to avert the onset of hypertension,” says Spatz.

    Totally healthy? Occasional SMBP can still be helpful. “Knowing how your blood pressure responds to periods of stress or lack of sleep can provide important mind-body connections, and may motivate you to take a more holistic approach to your cardiovascular health,” says Spatz.

    Just one caveat: Some people are unable to get an accurate blood pressure reading using these devices because of illness, birth defects or conditions such as an irregular heartbeat, so talk to your doctor about whether SMBP is right for you.


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