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Exercise and blood pressure.

Students use a blood pressure sensor to learn how to measure blood pressure and understand how aerobic exercise affects blood pressure parameters.

Supports NGSS Disciplinary Core Idea LS1.A

Grade Level: High School

Subject: Biology

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Wireless Blood Pressure Sensor with Standard Cuff

PASCO’s Wireless Blood Pressure Sensor allows students to quickly and easily measure both systolic and diastolic arterial blood pressure (mmHg) as well as heart rate (pulse in bpm).

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Source Collection: Lab #20

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Factors affecting Blood Pressure

Introduction: (initial observation).

In many animals, blood pressure is an indication of health status and a function of the circulatory system. Often, aged or over weight people complain that their blood pressure is low or high and take medicine to adjust their blood pressure. Obviously, what they feel is not the blood pressure itself, but instead they have learned to associate certain symptoms to the changes in their blood pressure. Blood pressure can not be felt; however, it can be measured using a Sphygmomanometer & a Stethoscope.

Every time that I hear about blood pressure imbalance, I am wondering what has caused it. Is it the age? Is it eating too much? Is it the hot weather? Is it because the person is tired?…

In this project I will study some of the factors that may possibly affect the blood pressure. The results of this research may provide alternative solutions to those suffering from high or low blood pressure.

This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “ Ask Question ” button on the top of this page to send me a message.

If you are new in doing science project, click on “ How to Start ” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Information Gathering:

Find out about blood pressure and the way it can be measured. Read books, magazines or ask professionals who might know in order to learn about the factors that may effect blood pressure. Keep track of where you got your information from.

Following are samples of information that you may gather.

What is blood pressure?

When the heart beats, blood is pumped to all parts of the body. Blood pressure is the force of blood on the walls of the blood vessels. Blood pressure is described by two numbers (like 120 / 80). The first and highest number (systolic) measures pressure when the heart is squeezing the blood out; the second and lower number (diastolic) measures the pressure when the heart is resting between beats.

To measure your blood pressure at home, you can use either an aneroid monitor or a digital monitor. The aneroid monitor has a dial gauge that is read by looking at a pointer. The cuff is inflated by hand, by squeezing a rubber bulb. Digital monitors have either manual or automatic cuffs. The blood pressure reading flashes on a small screen. Choose the type of monitor that best suits your needs.

Blood pressure varies relative to heart’s pumping of blood. The heart should be thought of as a dual pump, with a right and left side. Systole represents the active pumping of blood from the ventricles into the circulation. The right side of the heart takes venous/returning blood from the body and sends it to the lungs to be oxygenated ( pulmonary circulation ). Measuring blood pressures on the right side of the heart requires very complicated equipment. The left side of the heart takes the oxygenated blood and sends it to the rest of the body. When you take a blood pressure reading, you measure pressures in the systemic circulation .

The highest pressures occur during systole as blood is ejected into the aorta and subsequent arteries of the body. Diastole , the heart’s resting phase, follows systole. During diastole the ventricles fill with more blood. Systemic pressures fall until more blood is ejected during systole.

What do I need to do before I measure my normal blood pressure?

• Rest for 3 to 5 minutes before measuring your blood pressure. Do not talk.
• Sit in a comfortable position, with your legs and ankles uncrossed and your back supported.
• Place your arm, raised to the level of your heart, on a table or a desk, and sit still.
• Wrap the correctly sized cuff smoothly and snugly around the upper part of your bare arm. The cuff should fit snugly, but there should be enough room for you to slip one fingertip under the cuff.
• Be certain that the bottom edge of the cuff is 1 inch above the crease of your elbow.

How do I use an aneroid monitor?

• Put the stethoscope ear pieces into your ears, with the ear pieces facing forward.
• Place the stethoscope disk on the inner side of the crease of your elbow.
• Rapidly inflate the cuff by squeezing the rubber bulb to 30 to 40 points higher than your last systolic reading.
• Inflate the cuff rapidly, not just a little at a time. Inflating the cuff too slowly will cause a false reading.
• Slightly loosen the valve and slowly let some air out of the cuff. Deflate the cuff by 2 to 3 millimeters per second. If you loosen the valve too much, you won’t be able to determine your blood pressure.
• As you let the air out of the cuff, you will begin to hear your heartbeat. Listen carefully for the first sound.
• Check the blood pressure reading by looking at the pointer on the dial. This number will be your systolic pressure.
• Continue to deflate the cuff. Listen to your heartbeat. You will hear your heartbeat stop at some point. Check the reading on the dial. This number is your diastolic pressure.
• Write down your blood pressure, putting the systolic pressure before the diastolic pressure (for example, 120/80).
• If you want to repeat the measurement, wait 2 to 3 minutes before re-inflating the cuff.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to see how exercise affect blood pressure.

You may test other factors as you wish. Another factor that I like to test is drinking sugar water. I have seen some people ask for sugar water as soon as they feel their blood pressure is low. Some other variables or factors that may be tested are:

• hours of the day
• Eating dinner
• Air temperature (cold room – Hot room)
• Drinking water
• Caffeine (Coffee is a good source of caffeine)

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. Following are two sample hypothesis:

Hypothesis Example 1:

Since exercise consumes energy, human body will be weaker after the exercise and heart may not have enough energy to pump the blood at its highest pressure. So blood pressure will drop after the exercise.

Hypothesis Example 2:

When we exercise, body will need more oxygen, so heart will pump faster and that can temporarily increase our blood pressure. For this reason I think people who may get sick from high blood pressure must avoid heavy works.

Note that hypothesis does not have to be correct. Your experiments may support or reject your hypothesis.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1: Measure someone’s blood pressure

Introduction: This is just a warm-up experiment for you to learn measuring blood pressure and become good at it. To measure blood pressure, we use an external pressure to stop the flow of blood while we listen to the sound of blood flow using a stethoscope.

Note: It would be helpful if someone ( such as school nurse ) who knows how to take a blood pressure is present to supervise, as the technique requires some practice. Also you want to avoid keeping the cuff inflated on someone’s arm for too long.

Safety: Don’t put the cuff around your friend’s neck.. :).

How to do the experiment:

1. Deflate the bladder of the cuff and place it around the upper arm so it fits snugly, but not too tightly. If you’re right handed, you should hold the bulb/pump in your left hand to inflate the cuff. Hold it in the palm so your fingers can easily reach the valve at the top to open/close the outlet to the air bladder wrapped around the person’s arm.

2. Put the head of the stethoscope just under the edge of the cuff, a little above the crease of the person’s elbow. Hold it there firmly with the thumb, or with a few fingers of your right hand. Put the ear pieces of the stethoscope in your ears.

3. Inflate the cuff with brisk squeezes of the bulb. Watch the pressure gage as you do it. For most kids, you shouldn’t need to go over 150 (the markings indicate “pressure” in mm Hg or mercury).

4. At 150, slightly open the valve on the air pump (held in your left hand, as above). This part takes practice.. It’s important that you don’t let the air out too suddenly. Likewise, your friend will be quite irritated with you if you let it out too slowly.

5. Now, pay attention *very carefully* to what you hear through the stethoscope as the needle on the pressure gage falls. You will be listening for a slight “blrrpp” or a something that sounds like “prrpshh.” The first time you hear this sound, note what the reading was on the pressure gage. This value represents the systolic blood pressure (pressure when the heart is squeezing the blood out).

6. The sounds should continue and become louder in intensity. Note the pressure reading when you hear the sound for the last time. This value represents the diastolic blood pressure (pressure when the heart is resting between beats).

7. Afterwards, open the air valve completely to release any remaining pressure.

8. Repeat this experiment until you can quickly and effortlessly measure someone’s blood pressure.

Explanation:

The blood pressure cuff lets you apply external pressure to a circumferential ring around the upper arm. When the pressure is great enough, it forcibly closes the main artery of the upper arm – the brachial artery . The stethoscope allows you to hear when the underlying artery opens and closes as you release the air in the bladder.

Example – Take a person with a blood pressure of 120/80. The first number always represents systolic pressure (120), and the second number diastolic pressure (80). When you apply a pressure of 180mm Hg to the arm, the 120mm of pressure from the artery cannot overcome your externally applied pressure; the artery stays shut.

As you release the air out of the cuff, the external pressure falls. At 150mm the artery is still closed.. but at 119mm, it can open for just the slightest instant as the maximum/systolic pressure exceeds the applied pressure. Once the arterial pressure falls below 119mm, however, the artery shuts again. This opening and shutting produces the sounds you hear through the stethoscope (Korotkoff sounds). When the applied pressure falls below the diastolic/resting pressure, the artery stays open all the time.

Experiment 2: The effect of exercise on blood pressure (short term effects)

Introduction: In certain heart conditions and heart disease, even short term increase of blood pressure can be dangerous or deadly. It is important to know what factors may cause such an increase on blood pressure. In this experiment we test the effect of exercise (running) on blood pressure.

• Find five candidates for this experiment. Select all your candidates from same age and same sex and do all tests in the same day and in the same place so the environmental factors will remain the same. Number candidates from one to 5.
• Measure and record the blood pressure of all candidates.
• Ask candidates number 1 to 4 run a distance of about 250 feet and run back to you (so total running distance will be 500 feet). Immediately measure and record their blood pressure. They will run one at a time so you can measure their blood pressure immediately after running.
• Candidate number five is the control. He or she will not run. Measure and record the blood pressure of candidate number 5 again. This will usually show that any changes in the blood pressure of those who ran was not caused by other factors.
• Repeat the above procedure for a 1000 feet, 1500 feet and 2000 feet running distances. Record your results in a table like this:

Draw a graph:

Use the above result table to draw a line graph. Use X axis for running distance and Y axis for pressure. Use a separate color for each candidate. Use solid line for systolic number and dotted lines for diastolic number.

Materials and Equipment:

You will need:

• Blood pressure cuff
• Stethoscope

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

No calculation is required.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

List of References

http://www.drbloodpressure.com/05-mesurer.shtml

The Effects of Music on 6th Grade Boys’ Blood Pressure

http://scc.uchicago.edu/highbp.htm

http://users.tpg.com.au/users/amcgann/body/circulatory.html

http://www.cts.usc.edu/graphics/heart-crosssection1.jpg

http://www.tusculum.edu/faculty/home/ivanlare/html/101/outlines/24-circulation.html

http://www.emporia.edu/hper/pe768/cardio/adv/tsld001.htm

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Science Project

Lab: Measuring Heart Rate, Blood Pressure, and Pulse

Measuring Heart Rate Using a Stethoscope

Auscultation of the heart means to listen to and study the various sounds arising from the heart as it pumps blood. The heart sounds may be heard by placing the ear against the chest or by using a stethoscope

Parts of a Stethoscope

Earpieces: Also known as ear tips, these are the components that fit into the user's ears.

Tubing: The tubing of a stethoscope connects the earpieces to the chestpiece.

Chestpiece: This is the central component of the stethoscope that is placed against the patient's body to listen to internal sounds. The chestpiece typically consists of a diaphragm and a bell:

Diaphragm: The diaphragm is the flat, circular part of the chestpiece that is used to detect high-frequency sounds.

Bell: The bell is a smaller, cup-shaped component of the chestpiece that is used to detect low-frequency sounds.

*You can switch between the bell and diaphragm by rotating the stem connected to the chestpiece.

Label the parts of the stethoscope on the image. Use the underlined words.

Procedure: Place the diaphragm of the stethoscope at the center-left of the chest.

Two major sounds can be heard:

First heart sound - Produced at the beginning of systole when the atrioventricular (AV) valves close. This sound has a low-pitched tone commonly termed the “lub” sound of the heartbeat. Second heart sound - Occurs during the end of systole and is produced by the closure of the semilunar valves and the opening of the AV valves. The sound produced is higher pitched than the first heart sound. It is commonly referred to as the “dub” sound.

*Count the number of beats (lub-dubs) for thirty seconds. Multiply by two to get BPM (beats per minute).

Record data in the table on page 2.

Measuring Pulse

Pulse rate, which refers to the number of times a person's heart beats per minute (bpm), can be measured using various methods

Measure Using Your Radial Artery

To find your radial artery (the most common point from which people take pulses), hold one hand straight out,elbow bent, palm relaxed and facing up. Raise your thumb slightly skyward to create a small pocket under your thumb at the top of your wrist where you will place the tips of your index and middle finger.

Do not use your thumb--it's also got a pulse and could cause counting confusion. * Count the beats for 30 seconds and multiply by two. This is your pulse rate. Record data for yourself and one other subject in the data table.

Measure Using Your Carotid artery

Neck pulse points are stronger and more accessible. The carotid is located just below your jaw in the groove where your head and neck meet. Use your index and middle fingertips to feel for a pulsation.

*Complete data table.

Lab: Measuring Blood Pressure

Materials: Sphygmomanometer (blood pressure cuff)

Blood pressure is measured in millimeters of mercury (mm Hg). A typical blood pressure is 120/80. The first number represents when the heart contracts and is called the systolic pressure. The second, lower number, is when the heart relaxes and is called the diastolic pressure.

How to Use a Sphygmomanometer

1. Deflate the air bladder of the cuff and place it around the upper arm so it fits snugly, but not too tight. If you’re right handed, you should hold the bulb/pump in your left hand to inflate the cuff. Hold it in the palm so your fingers can easily reach the valve at the top to open and close the outlet to the air bladder.

2. Put the head of the stethoscope just under the edge of the cuff, a little above the crease of the person’s elbow. Hold it there firmly with the thumb or with the fingers of the right hand.

3. Inflate the cuff with brisk squeezes of the bulb. Watch the pressure gauge as you do it, you should go to around 150 mmHg or until the pulse is no longer heard. At this point blood flow in the underlying blood vessel is cut off by pressure in the cuff.

4. At around 150, slightly open the valve on the air pump (held in your left hand). This part takes practice, it’s important that you don’t let the air out too suddenly or too slowly.

5. Now, pay attention to what you hear through the stethoscope as the needle on the pressure gauge falls. You will be listening for the “thump” sound. The first time you hear this sound; note the reading on the gauge and immediately following you should hear the sound of a pulse.

This value is the systolic blood pressure.

6. The sounds should continue and become louder in intensity. Note the reading when you hear the sound for the last time. This is the diastolic blood pressure.

Record as systolic / diastolic (Shown on image 126 / 72)

7. Afterwards, open the air valve completely to release any remaining pressure.

8. Record your readings in the data table.

Analysis Questions:

1. Compare the systole to diastole. Describe what happens in each and how that relates to a person’s blood pressure reading.

2. What equipment is used to measure heart rate? To measure blood pressure?

3. Why is using your thumb to measure pulse not ideal?

4. Was the pulse rate, and heart rate the same for both subjects? Suggest a reason for why there is variation.

5. In your own words, describe how to use a blood pressure cuff (sphygmomanometer).

6. Doctors and nurses usually have their own personal stethoscope. Suggest a reason why this equipment is not shared.

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Heart Health

Meditation and a relaxation technique to lower blood pressure

Several practices that help calm the mind can also lower blood pressure. All are types of meditation, which use different methods to reach a state sometimes described as "thoughtful awareness" or "restful alertness."

Researchers are now beginning to better understand how these mental changes affect the cardiovascular system. A number of well-designed studies show that meditation can modestly lower blood pressure, according to an American Heart Association scientific statement published in the journal Hypertension .

Blood pressure benefits of quieting the brain

A related technique, designed to evoke the so-called relaxation response, has been found to be helpful with high blood pressure and other disorders caused or made worse by stress. The technique, developed by Dr. Herbert Benson, director emeritus of the Harvard-affiliated Benson-Henry Institute for Mind Body Medicine, is the opposite of the stress-induced fight-or-flight response. This self-induced quieting of brain activity has aspects of both transcendental meditation and mindfulness meditation.

In one of Dr. Benson's studies, elderly people with hard-to-treat isolated systolic hypertension underwent relaxation response training. The study participants were more likely to be able to control their blood pressure to the point whereby some could reduce and even eliminate their blood pressure medications.

Further research revealed that when blood pressure falls during the relaxation response, inflammation and blood vessel constriction become less active and blood vessels widen. This benefit appears to be mediated by nitric oxide, a molecule made in the body that (among other things) helps relax and widen blood vessels, keeping blood pressure under control.

Another small study found that people who practiced the relaxation response for eight weeks had higher levels of nitric oxide in their breath, while a control group showed no such change.

Dr. Benson recommends practicing the relaxation response twice a day, for 10 to 20 minutes, similar to what other meditation experts recommend.

Here's how to do it.

• Sit in a quiet place with your eyes closed.
• Relax your muscles and silently repeat a word, phrase, sound, or short prayer of your choosing over and over.
• When stray thoughts interfere (as they will), let them come and go and return to your word, phrase, or sound.

For more on getting your blood pressure under control, buy Controlling Your Blood Pressure, a Special Health Report from Harvard Medical School.

Image: Zinkevych/Getty Image

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No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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Principles and techniques of blood pressure measurement

Gbenga ogedegbe.

a Associate Professor of Medicine and Director, Center for Healthful Behavior Change, Division of General Internal Medicine, NYU School of Medicine, New York

Thomas Pickering

b Professor of Medicine, Center for Behavioral Cardiovascular Health, Columbia University, New York (deceased)

Although the mercury sphygmomanometer is widely regarded as the “gold standard” for office blood pressure measurement, the ban on use of mercury devices continues to diminish their role in office and hospital settings. To date, mercury devices have largely been phased out in US hospitals. This has led to the proliferation of non-mercury devices and has changed (probably for ever) the preferable modality of blood pressure measurement in clinic and hospital settings. In this article, the basic techniques of blood pressure measurement and the technical issues associated with measurements in clinical practice are discussed. The devices currently available for hospital and clinic measurements and their important sources of error are presented. Practical advice is given on how the different devices and measurement techniques should be used. Blood pressure measurements in different circumstances and in special populations such as infants, children, pregnant women, elderly persons, and obese subjects are discussed.

Basic techniques of blood pressure measurement

Location of measurement.

The standard location for blood pressure measurement is the brachial artery. Monitors that measure pressure at the wrist and fingers have become popular, but it is important to realize that systolic and diastolic pressures vary substantially in different parts of the arterial tree with systolic pressure increasing in more distal arteries, and diastolic pressure decreasing.

The auscultatory method

Although the auscultatory method using mercury sphygmomanometer is regarded as the ‘gold standard’ for office blood pressure measurement, widespread implementation of the ban in use of mercury sphygmomanometers continues to diminish the role of this technique. 72 The situation is made worse by the fact that existing aneroid manometers, which use this technique, are less accurate and often need frequent calibration. 72 New devices known, as “hybrid” sphygmomanometers, have been developed as replacement for mercury devices. Basically, these devices combine the features of both electronic and auscultatory devices such that the mercury column is replaced by an electronic pressure gauge, similar to oscillometric devices, but the blood pressure is taken in the same manner as a mercury or aneroid device, by an observer using a stethoscope and listening for the Korotkoff sounds. 72

The oscillometric technique

This was first demonstrated by Marey in 1876, 38 and it was subsequently shown that when the oscillations of pressure in a sphygmomanometer cuff are recorded during gradual deflation, the point of maximal oscillation corresponds to the mean intra-arterial pressure. 32 , 39 , 97 The oscillations begin at approximately systolic pressure and continue below diastolic ( Fig. 1 ), so that systolic and diastolic pressure can only be estimated indirectly according to some empirically derived algorithm. This method is advantageous in that no transducer need be placed over the brachial artery, and it is less susceptible to external noise (but not to low frequency mechanical vibration), and that the cuff can be removed and replaced by the patient during ambulatory monitoring, for example, to take a shower. The main disadvantage is that such recorders do not work well during physical activity when there may be considerable movement artifact. The oscillometric technique has been used successfully in ambulatory blood pressure monitors and home monitors. It should be pointed out that different brands of oscillometric recorders use different algorithms, and there is no generic oscillometric technique. Comparisons of several different commercial models with intra-arterial and Korotkoff sound measurements, however, have shown generally good agreement. 6 , 79

Changes occurring distal to a sphygmomanometer cuff during deflation. Upper trace : Korotkoff sounds. Second trace : cuff pressure. Third trace : oscillations in cuff pressure. The maximal oscillation occurs at a pressure of 108 mm Hg, the mean arterial pressure. Bottom trace : radial pulse. From Pickering TG. Blood pressure variability and ambulatory monitoring. Curr Opin Nephrol Hypertens 1993a;2:380; with permission

Ultrasound techniques

Devices incorporating this technique use an ultrasound transmitter and receiver placed over the brachial artery under a sphygmomanometer cuff. As the cuff is deflated, the movement of the arterial wall at systolic pressure causes a Doppler phase shift in the reflected ultrasound, and diastolic pressure is recorded as the point at which diminution of arterial motion occurs. Another variation of this method detects the onset of blood flow at systolic pressure, which has been found to be of particular value for measuring pressure in infants and children. 18 In patients with very faint Korotkoff sounds (for example those with muscular atrophy) placing a Doppler probe over the brachial artery may help to detect the systolic pressure, and the same technique can be used for measuring the ankle-brachial index, in which the systolic pressures in the brachial artery and the posterior tibial artery are compared, to obtain an index of peripheral arterial disease.

The finger cuff method of Penaz

This interesting method was first developed by Penaz 63 and works on the principle of the “unloaded arterial wall.” Arterial pulsation in a finger is detected by a photo-plethysmograph under a pressure cuff. The output of the plethysmograph is used to drive a servo-loop, which rapidly changes the cuff pressure to keep the output constant, so that the artery is held in a partially opened state. The oscillations of pressure in the cuff are measured and have been found to resemble the intra-arterial pressure wave in most subjects ( Fig. 2 ). This method gives an accurate estimate of the changes of systolic and diastolic pressure when compared to brachial artery pressures; 63 the cuff can be kept inflated for up to 2 hours. It is now commercially available as the Finometer and Portapres recorders and has been validated in several studies against intra-arterial pressures. 61 , 84 The Portapres enables readings to be taken over 24 hours while the subjects are ambulatory, although it is somewhat cumbersome. 27

Recording of systolic pressure during laboratory stress testing, made simultaneously with a continuous beat-to-beat monitor (Finapres) and an intermittent oscillometric device (Colin). Cp = cold pressor test; hg = handgrip; ma = mental arithmetic; ta = talking.

Technical issues with measurement from the arm

There are important potential sources of error with measurements from the upper arm, which are discussed in the following sections.

Effects of posture

There is no consensus as to whether blood pressure should be routinely measured while seated or supine, although most guidelines recommend sitting. 67 , 72 In a survey of 245 subjects of different ages, Netea et al found that systolic pressures were the same in both positions, but there was a systematic age-related discrepancy for diastolic pressure such that at the age of 30 the sitting diastolic was about 10 mm Hg higher than the supine reading, whereas at the age of 70 the difference was only 2 mm Hg. 49

Body position

Blood pressure measurements are also influenced by the position of the arm. 45 , 47 , 48 , 94 As shown in Fig. 3 , there is a progressive increase in the pressure of about 5 to 6 mm Hg as the arm is moved down from the horizontal to vertical position. These changes are exactly what would be expected from the changes of hydrostatic pressure. It is also important that the patient’s back be supported during the measurement; if the patient is sitting bolt upright the diastolic pressure may be up to 6.5 mm Hg higher than if sitting back. 14

The effects of varying arm position on blood pressure recorded from the brachial artery. From Pickering TG. Blood pressure variability and ambulatory monitoring. Curr Opin Nephrol Hypertens 1993a;2:380; with permission.

Cuff-inflation hypertension

Although in most patients the act of inflating a sphygmomanometer cuff does not itself change the blood pressure, as shown by intra-arterial 62 and Finapres 87 recordings, in occasional patients there may be a transient but substantial increase of up to 40 mm Hg coinciding with cuff inflation. 42 This condition appears to be distinct from white coat hypertension, in which the increase in pressure both precedes the act of inflation and outlasts it. It should also be differentiated from the transient increase of blood pressure that occurs during self-measurement, due to the muscular act of inflating the cuff.

The size of the cuff relative to the diameter of the arm is critical. The most common mistake is to use a cuff that is too small, which will result in an overestimation of the pressure. 33 , 40 , 86 In general, this error can be reduced by using a large adult sized cuff for all except the skinniest arms. The British Hypertension Society (BHS) recommends that if the arm circumference exceeds 33 cm, a large adult cuff should be used (width 12.5 to 13 cm, length 35 cm). 67 In the United States, the most widely advocated protocol for the selection of the appropriate cuff size is the one recommended by the American Heart Association, 64 shown in Table 1 .

Cuff sizes recommended by the American Heart Association

Validation of monitors

The increasing use of electronic monitors for both self-and ambulatory monitoring has necessitated the development of standard protocols for testing them. The two most widely used have been developed by the BHS 52 and Association for the Advancement of Medical Instrumentation (AAMI) in the United States. 2 Both require the taking of three blood pressure readings in 85 subjects (chosen to have a variety of ages and blood pressures) by trained observers and the device being tested. The BHS protocol requires that a device must give at least 50% of readings within 5 mm Hg and 75% within 10 mm Hg with the two methods (grade B), and the AAMI requires that the average difference between the two methods not exceed 5 mm Hg with a standard deviation of less than 8 mm Hg. One of the limitations of the validation procedures is that they analyze the data on a population basis and pay no attention to individual factors. Thus, it is possible that a monitor will pass the validation criteria and still be consistently in error in a substantial number of individuals. 23

Devices for clinic and hospital measurement

Mercury sphygmomanometers.

The design of mercury sphygmomanometers has changed little over the past 50 years, except that modern versions are less likely to spill mercury if dropped. As indicated earlier, although the use of mercury sphygmomanometer is widely regarded as the ‘gold standard’ for office blood pressure measurement, widespread implementation of the ban in use of mercury devices continues to diminish their role in office and hospital settings. To date, mercury devices have largely being phased out in US hospitals. 43 The reason is not because any more accurate device has been developed but because of concerns about the safety of mercury. Currently the two alternatives for replacement of mercury are aneroid sphygmomanometer and electronic (oscillometric) devices.

Aneroid devices

The ban on mercury sphygmomanometer has placed new interest in alternative methods, of which aneroid devices are the leading contenders. The error rates reported with regards to accuracy of aneroid devices in older hospital surveys range from 1% in one survey, 8 to 44% in another. 44 Validation studies conducted a decade ago indicated that they could be accurate. 4 , 96 A most recent study, which compared the use of mercury versus aneroid device in the setting of a large clinical trial across over 20 clinical sites, also found it to be accurate. 36 This is the best evidence yet attesting to the accuracy of aneroid devices.

Sources of error with the auscultatory method

Some of the major causes of a discrepancy between the conventional clinical measurement of blood pressure and the true blood pressure are listed in Table 2 . The measurement of blood pressure typically involves an interaction between the patient and the physician (or whoever is taking the reading), and factors related to both may lead to a tendency to either overestimate or underestimate the true blood pressure or to act as a source of bi-directional error. As shown in Table 2 , there may be activities that precede or accompany the measurement that make it unrepresentative of the patient’s “true” pressure. These include exercise and smoking before the measurement as well as talking during it.

Patient- and physician-related factors that lead to a discrepancy between clinic and true BP

The white coat effect and white coat hypertension

One of the main reasons for the growing emphasis on blood pressure readings taken outside the physician’s office or clinic is the white coat effect, which is conceived as the increase of blood pressure that occurs at the time of a clinic visit and dissipates soon thereafter. Recent studies indicate that the mechanisms underlying the white coat effect may include anxiety, a hyperactive alerting response, or a conditioned response 29 , 55 In one of these studies, we assessed office blood pressure, ambulatory blood pressure, and anxiety scores on three separate occasions one month apart in 238 patients. We found the largest white coat effect occurred in the physician’s presence, and the noted white coat effect was a conditioned response to the medical environment and the physician’s presence rather than a function of the patients’ trait anxiety level (See Figure 4 ). The white coat effect is seen to a greater or lesser extent in most if not all hypertensive patients but is much smaller or absent in normotensive individuals. It usually has been defined as the difference between the clinic and daytime ambulatory pressure. 91 A closely linked but discrete entity is white coat hypertension, which refers to a subset of patients who are hypertensive according to their clinic blood pressures but normotensive at other times. Thus, white coat hypertension is a measure of blood pressure levels, whereas the white coat effect is a measure of blood pressure change.

Self-rated anxiety score before (pre) and after (post) BP (BP) measurement in different conditions. On day 1, the research assistant (RA) measured BP outside the medical environment using a mercury sphygmomanometer (SPH). On day 2, the RA measured BP in the absence of a physician (MD) by manually triggering a device for ambulatory BP measurement (MTD) first in the waiting room and next in the examination before and after the MD measured BP using SPH. Anxiety scores were obtained in normotensive subjects (NT) and in patients with white coat hypertension (WC-HT), masked hypertension (M-HT), and sustained hypertension (S-HT). Reproduced with permission from Ogedegbe G, Pickering TG, Clemow L, et al. The misdiagnosis of hypertension: the role of patient anxiety. Arch Intern Med. Dec 8 2008; 168(22): 2459–2465.

What distinguishes patients with white coat hypertension from those with true or sustained hypertension is not that they have an exaggerated white coat effect but that their blood pressure is within the normal range when they are outside the clinic setting. White coat hypertension is important clinically because it appears to be a relatively low-risk condition compared to sustained hypertension (defined by an elevated blood pressure in both the clinic and ambulatory settings). 19 It can only be diagnosed reliably by ambulatory monitoring and home self-monitoring as described later. Observer error and observer bias are important sources of error when sphygmomanometers are used. Differences of auditory acuity between observers may lead to consistent errors, and digit preference is very common, with most observers recording a disproportionate number of readings ending in 5 or 0. 60 An example is shown in Fig. 5 of readings taken by hypertension specialists, who are clearly not immune to this error. The average values of blood pressure recorded by trained individual observers have been found to vary by as much as 5 to l0 mm Hg. 17 The level of pressure that is recorded may also be profoundly influenced by behavioral factors related to the effects of the observer on the subject, the best known of which is the presence of a physician. It has been known for more than 40 years that blood pressures recorded by a physician can be as much as 30 mm Hg higher than pressures taken by the patient at home, using the same technique and in the same posture. 3 Physicians also record higher pressures than nurses or technicians. 37 , 73 Other factors that influence the pressure that is recorded may include both the race and sex of the observer. 12 , 41

The percentage of terminal digits chosen by four physicians in a Hypertension Clinic during routine blood pressure measurement. Note the marked preference for zeroes in physicians C and D.

Rate of cuff inflation and deflation

The rate of inflation has no significant effect on the blood pressure, 33 but with very slow rates of deflation (2 mm Hg/s or less) the intensity of the Korotkoff sounds was diminished, resulting in slightly higher diastolic pressures. This effect has been attributed to venous congestion reducing the rate of blood flow during very slow deflation. 26 The generally recommended deflation rate is 2 to 3 mm Hg/s. The rate of inflation and deflation is of crucial importance during self-monitoring of blood pressure, because the isometric exercise involved in inflating the cuff produces a transient elevation of pressure of about 10 mm Hg. 88 Although this lasts for only about 20 seconds, if the cuff is deflated too soon the pressure may not have returned to baseline, and a spuriously high systolic pressure will be recorded.

Auscultatory gap

This can be defined as the loss and reappearance of Korotkoff sounds that occur between systolic and diastolic pressures during cuff deflation in the absence of cardiac arrhythmias. Thus, if its presence is not recognized, it may lead to the registration of spuriously high diastolic or low systolic pressures. It may occur either because of phasic changes of arterial pressure or in patients who have faint Korotkoff sounds ( Fig. 6 ). The auscultatory gap may pose a problem for automatic recorders, which operate by the Korotkoff sound technique, and result in gross errors in the measurement of diastolic pressure. 26 Oscillometric devices are less susceptible to this problem. 26 Its presence is of clinical significance, because it is associated with an increased prevalence of target organ damage. 9

The phenomenon of the auscultatory gap during cuff deflation. Upper trace: ECG. Second trace: low frequency recording of sounds under the sphygmomanometer cuff. Third trace: Korotkoff sounds. Fourth trace: auscultatory marker pressed when systolic and diastolic sounds were heard. Fifth trace: cuff pressure. Sixth trace: Finapres recording of arterial pressure; note oscillations of pressure corresponding to silent period of K sounds. From Pickering TG. Blood pressure variability and ambulatory monitoring. Curr Opin Nephrol Hypertens 1993a;2:380; with permission.

Technical sources of error

There are also technical sources of error with the auscultatory method, although these are usually fewer when a mercury column is used than when many of the semiautomatic methods are in use (see later). These error sources include the position of the column, which should be at approximately the level of the heart. The mercury should read zero when no pressure is applied, and it should fall freely when the pressure is reduced (this may not occur if the mercury is not clean or if the pin-hole connecting the mercury column to the atmosphere is blocked). With aneroid meters, it is essential that they be checked against a mercury column both at zero pressure and when pressure is applied to the cuff. Surveys of such devices used in clinical practice frequently have shown them to be inaccurate. 7

Electronic monitors for self-monitoring of blood pressure

When home monitoring was first used, most studies used aneroid sphygmomanometers. 34 More recently however, automatic electronic devices have become more popular. A Gallup poll conducted in 2005 indicated an increase in the number of patients monitoring their blood pressure at home from 38% in 2000 to 55% in 2005. Similarly the proportion of patients owning a monitor increased from 49% in 2000 to 64% in 2005. 74 The standard type of monitor for home use is now an oscillometric device that records pressure from the brachial artery. These have the advantage of being easy to use, because cuff placement is not as critical as with devices that use a Korotkoff sound microphone, and the oscillometric method has in practice been found to be as reliable as the Korotkoff sound method. The early versions were mostly inaccurate 85 but the currently available ones are often satisfactory. 22 , 53 The advantages of electronic monitors have begun to be appreciated by epidemiologists, 13 who have always been greatly concerned about the accuracy of clinical blood pressure measurement and have paid much attention to the problems of observer error, digit preference, and the other aforementioned causes of inaccuracy. Cooper et al have made the case that the ease of use of the electronic devices and the relative insensitivity to whom is actually taking the reading can outweigh any inherent inaccuracy compared to the traditional sphygmomanometer method. 13 Patients should be advised to use only monitors that have been validated for accuracy and reliability according to standard international testing protocols. Unfortunately, only a few of the devices that are currently on the market has been subjected to proper validation tests, such as the AAMI and BHS. An up-to-date list of validated monitors is available on the Dabl Educational Web site ( http://www.dableducational.org ) and the British Hypertension Society Web site ( http://www.bhsoc.org/default.stm ).

Wrist monitors

These monitors have the advantages of being smaller than the arm devices and can be used in obese people, as the wrist diameter is little affected by obesity. A potential problem with wrist monitors is the systematic error introduced by the hydrostatic effect of differences in the position of the wrist relative to the heart, 45 as shown in Fig. 7 . This can be avoided if the wrist is always at heart level when the readings are taken, but there is no way of knowing retrospectively whether this was complied with when a series of readings are reviewed. Wrist monitors have potential but need to be evaluated further. 16 , 95

The effects of changes in the position of the forearm on the blood pressure recorded by a wrist monitor. Ten readings were taken in each of three positions: vertically down, horizontal, and vertically up. The average values are shown at the top of each bar.

Finger monitors

Although these monitors are convenient, they have so far been found to be inaccurate and therefore should not be used. 74

Ambulatory monitors

First developed almost 40 years ago, ambulatory blood pressure monitoring is only now beginning to find acceptance as a clinically useful technique. Recent technologic advances have led to the introduction of monitors that are small and relatively quiet and that can take up to 100 readings of blood pressure over 24 hours while patients go about their normal activities. They are reasonably accurate while the patient is at rest but less so during physical activity. When last systematically surveyed (in 2001), only 24 had been validated according to the AAMI or BHS criteria, of which only 16 satisfied the criteria for accuracy 53 Now many more monitors have been validated and an updated list can be found on the Dabl Educational Web site ( http://www.dableducational.org ). They can in theory provide information about the three main measures of blood pressure: the average level, the diurnal variation, and short-term variability. Recordings in hypertensive patients show that in most patients the average ambulatory pressure is lower than the clinic pressure, and in some cases it may be within the normal range, leading to a diagnosis of white coat hypertension, described later. Given that there is a discrepancy between the clinic and ambulatory pressure, it is reasonable to suppose that the prediction of risk will be different. There are now more than 30 cross-sectional studies relating the extent of cardiovascular damage to both clinic and ambulatory pressures. 68 Almost all have shown that the correlation coefficients are higher for ambulatory pressure, although in many instances the differences were small. The superiority of ambulatory pressure in this respect may be attributed at least in part to the greater number of readings and to their more representative nature.

Measurement in different situations

Clinic measurement.

The recent interest in alternative methods of measuring blood pressure has served to emphasize some of the potentially correctable deficiencies of the routine clinic measurement of blood pressure. By increasing the number of readings taken per visit and the number of visits as well as by attempting to eliminate sources of error such as digit preference, the reliability of clinic pressure for estimating the true blood pressure and its consequences can be greatly increased. Despite this, it must be remembered that there are a substantial number of subjects with white coat hypertension in whom clinic readings will continue to give unrepresentative values, no matter how many measurements are taken. Surveys of the techniques used by physicians and nurses in actual practice make depressing reading. One performed in a teaching hospital found that not one out of 172 workers followed the American Heart Association guidelines for measuring blood pressure in the clinic setting. Although 68% considered the mercury sphygmomanometer to be the most accurate, only 38% chose to use it when given a choice, and 60% were judged to be taking blood pressure inaccurately. 93

Self-measurement

The potential advantages of having patients take their own blood pressure are twofold: the distortion produced by the white coat effect is eliminated, and multiple readings can be taken over prolonged periods. Self-measurement of blood pressure at home has been shown to be useful in predicting target organ damage, cardiovascular events and mortality. 74 Five prospective studies have compared the prediction of morbid events with the use of both conventional office and home blood pressure. Three were based on population samples, and 2 recruited hypertensive patients. Four studies found that home BP was the stronger predictor of risk. The fifth found that both BP measures predicted risk. 5 , 20 , 57 , 59 , 80 The most recent population-based study of comparative prognosis of self-monitoring versus office BP in predicting cardiovascular events and total mortality among 2081 adults, was the Finn-Home Study. 51 Although home BP and office BP were strongly associated with cardiovascular events in separate Cox proportional hazard models, when both modalities were included in the model, home BP (Hazard Ratio [HR], 1.22/1.15; 95% CI, 1.09 to 1.37/1.05 to 1.26) was remained a strong predictor of cardiovascular events per 10/5 mm Hg increase in blood pressure, while office BP was not predictive (HR, 1.01/1.06; 95% CI, 0.92 to 1.12/0.97 to 1.16). Similarly, home systolic blood pressure was the only predictor of total mortality (HR, 1.11; 95% CI, 1.01/1.23)). This study is the second population-based study to conclusively confirm the superior prognostic value of home BP versus office Bp on total mortality. The concern about the potential for observer error than with physician readings can often be mitigated by use of automated devices with memory chips. These allow the physician to recall the blood pressure readings taken by their patients. Whereas exclusive reliance on self-monitored readings is not recommended, they can provide a useful adjunct to clinic readings, both for the initial evaluation of newly diagnosed patients and for monitoring their response to treatment.

Ambulatory blood pressure monitoring

There are six prospective studies to date showing that ambulatory blood pressure is a better predictor of risk than clinic pressure and more are on the way. The first, published by Perloff et al., 65 , 66 used noninvasive monitoring performed during the day only and reported that those whose ambulatory pressure was low in relation to their clinic pressure were at lower risk of morbidity. The second, by Verdecchia et al., 90 followed a group of 1187 normotensive and hypertensive individuals for 3 years; hypertensive subjects were classified as having white coat or sustained hypertension. The morbid event rate was 0.49 per 100 patient-years in white coat hypertensive patients (similar to the rate of 0.47 in the normotensive subjects), whereas it was 1.79 in hypertensive dippers, who constituted the majority, and 4.99 in nondippers. The third study is the pilot results of a population study in Ohasama, Japan, 58 which reported that ambulatory pressure was a better predictor of morbidity than screening pressure; no attempt was made to classify individuals as having white coat hypertension. The fourth 77 is a study of patients with refractory hypertension, defined as a diastolic pressure above 100 mm Hg while on three or more antihypertensive medications. Patients were classified in three groups according to their daytime ambulatory pressure; those in the lowest tertile (below 88 mm Hg) had a significantly lower rate of morbidity over the next 4 years, despite similar clinic pressures. A fifth study, from Northwick Park Hospital in London, 30 followed 479 patients for nearly 10 years, all of whom were initially evaluated with intra-arterial ambulatory blood pressure monitoring using the intra-arterial technique. Patients were classified as having white coat or sustained hypertension, and it was found that a diagnosis of white coat hypertension was associated with one-third the risk of cardiovascular morbidity as sustained hypertension. The sixth study in this series is Syst-Eur, a large placebo-controlled study of the effects on cardiovascular morbidity of treating systolic hypertension of the elderly with a calcium channel blocker. A substudy of 808 patients used ambulatory blood pressure monitoring, and found that ambulatory blood pressure was a much more potent predictor of risk than office blood pressure. 83 The findings from these older studies were confirmed by more recent data in other prospective studies. Thus, although these prognostic studies differed widely in their design, ranging from a population study to one of refractory hypertensive subjects, the results all point in the same direction, namely that ambulatory pressure gives a better prediction of prognosis after controlling for clinic pressure, the corollary of which is that patients with white coat hypertension have a more benign prognosis than those with sustained hypertension.

How should different blood pressure measurement techniques be used?

Which measures of blood pressure are clinically important.

There are potentially three major measures of blood pressure that could contribute to the adverse effects of hypertension. The first is the average or “true” level, the second is the diurnal variation, and the third the short-term variability.

Average clinic blood pressure

Presently, epidemiologic and clinical data are available only for the average level of blood pressure. In clinical practice, a patient’s blood pressure is typically characterized by a single value of the systolic and diastolic pressures, to denote the average level. Such readings are normally taken in a clinic setting, but there is extensive evidence that in hypertensive patients, clinic pressures are consistently higher than the average 24-hour pressures recorded with ambulatory monitors. 70 This overestimation by clinic readings of the true pressure at high levels of pressure and underestimation at low levels has been referred to as the regression dilution bias and means that the slope of the line relating blood pressure and cardiovascular morbidity should be steeper for the true blood pressure than for the clinic pressure. 71

Diurnal variation in blood pressure

There is a pronounced diurnal rhythm of blood pressure, with a decrease of 10 to 20 mm Hg during sleep and a prompt increase on waking and rising in the morning. The highest blood pressures are usually seen between 6 AM and noon, which is also the time at which the prevalence of many cardiovascular morbid events tends to be highest. 46 The pattern of blood pressure during the day is to a large extent dependent on the pattern of activity, with pressures tending to be higher during the hours of work and lower while at home. 11 In hypertensive patients, the diurnal blood pressure profile is reset at a higher level of pressure, with preservation of the normal pattern in the majority. The short-term blood pressure variability is increased when expressed in absolute terms (mm Hg), but the percentage changes are no different. Thus, hypertension can be regarded as a disturbance of the set point or tonic level of blood pressure with normal short-term regulation. Antihypertensive treatment reverses these changes, again by resetting the set point toward normal, with little effect on short-term variability. The normal diurnal rhythm of blood pressure is disturbed in some hypertensive individuals, with loss of the normal nocturnal fall of pressure. This has been observed in a variety of conditions, including malignant hypertension, chronic renal failure, several types of secondary hypertension, pre-eclampsia, and conditions associated with autonomic neuropathy. 71 There is ample evidence linking elevated nighttime blood pressure to increased cardiovascular morbidity and mortality compared to daytime blood pressure. In the Ohasamma population-based study, a 5% reduction in night time BP resulted in up to 20% higher risk of cardiovascular mortality 56 . Similarly, a 9 mm Hg increase in nighttime diastolic BP was associated a 25% increased risk of congestive heart failure among elderly Swedish men. 28 In the Sys-Eur trial, 83 a large placebo-controlled study of the effects on cardiovascular morbidity of treating systolic hypertension of the elderly with a calcium channel blocker, a substudy of 808 patients used ambulatory blood pressure monitoring. Staessen et al found that nighttime blood pressure was a better predictor of cardiovascular morbidity and mortality than daytime blood pressure. 83 Although these findings are not sufficiently well established to be applied to routine clinical practice, the clinical significance of nocturnal hypertension and nondipping status cannot be ignored for long, given the potential beneficial effect of the treatment of nocturnal hypertension on cardiovascular disease risk reduction in hypertensive patients. 10

Blood pressure variability

Information on the clinical significance of blood pressure variability has accumulated over the past decade with recent data suggesting that increased ambulatory blood pressure variability is associated with the development of early carotid arteriosclerosis, 78 and a high rate of cardiovascular morbidity. 31 More recently, in a prospective ambulatory blood pressure study of initially untreated sample of 2649 hypertensive patients, Vedecchia and colleagues compared the independent prognostic value of daytime and nighttime blood pressure variability for cardiovascular events. They found elevated nighttime systolic blood pressure to be an independent predictor of cardiac events. 89 Similarly, among elderly patients in the Syst-Eur trial, increased nighttime systolic blood pressure variability on admission to the Syst-Eur trial was an independent risk factor for stroke during the trial among those in the placebo arm of the trial. (refs Systolic blood pressure variability as a risk factor for stroke and cardiovascular mortality in the elderly hypertensive population. 75

The combined use of clinic, home, and ambulatory monitoring

The measurement of clinic blood pressure, either by use of automated devices or conventional sphygmomanometry, will continue to be the principal method of clinical evaluation. A cardinal rule is that the closer the blood pressure is to the threshold level at which treatment will be started, the more readings should be taken over more visits, before treatment decision is made. In patients who have persistently elevated clinic pressure and evidence of blood pressure–related target organ damage, it is usually unnecessary to supplement the clinic readings with other types of measurement before reaching a therapeutic decision. When an elevated blood pressure is the only detectable abnormality, however, the possibility that the clinic pressure may overestimate the true pressure should be considered. This can be done either by self-monitoring or by ambulatory monitoring. A schema for the use of the different procedures for measuring blood pressure when evaluating a newly diagnosed hypertensive patient is shown in Fig. 8 . If self-monitoring is chosen and reveals pressures comparable to the clinic value, treatment may be appropriate; but if the home readings are much lower than the clinic readings, it does not rule out the possibility that the blood pressure may be elevated at work. This is the advantage of ambulatory monitoring, which gives the best estimate of the full range of blood pressure experienced during everyday life.

Schema for combining different measures of blood pressure in the evaluation of patients with suspected hypertension.

Measurement of blood pressure in special populations and circumstances

Infants and children.

The Korotkoff sound technique is recommended as the standard for children older than the age of 1 year; however, it may give systematic errors in infants, in whom the sounds are difficult to hear, and thus the true systolic pressure may be underestimated. 18 In infants the best indirect measurement technique is an ultrasonic flow detector. 76 A particular problem associated with blood pressure measurement in children of different ages is knowing which sized cuff to choose. The BHS recommends choosing from three cuff sizes—4×13 cm, 8×18 cm, and 12×35 cm (adult cuff)—and putting on the widest cuff that will fit the arm. 15 The American Heart Association, 64 and the National High Blood Pressure Education Program (NHBPEP), 1 have recommended that the cuff size be standardized to the circumference of the arm.

Pregnant women

In normal pregnancy there is a fall of blood pressure, together with an increase of cardiac output and a large decrease of peripheral resistance. As a result of this hyperkinetic state, Korotkoff-like sounds occasionally may be heard over the brachial artery without any pressure being applied to the cuff. These sounds are most probably due to turbulent flow in the artery. Consequently, the use of phase 4 has frequently been recommended for registering diastolic pressure in pregnant women, which may be 12 mm Hg higher than phase 5. 92 The NHBPEP Working Group report recommends recording both phases 4 and 5 throughout pregnancy. 35 In one study of 85 pregnant women, however, phase 5 never approached zero, and phase 4 could be identified in only half, leading the authors to recommend phase 5. 81

Elderly patients

In some older people there is an increase of systolic pressure without a corresponding increase of diastolic pressure (systolic hypertension), which has been attributed to a diminished distensibility of the arteries with increasing age. In extreme cases this may result in a diminished compressibility of the artery by the sphygmomanometer cuff, so that falsely high readings may be recorded, often referred to as pseudohypertension of the elderly. 82 These patients represent the exception rather than the rule, however, because studies of healthy elderly subjects have not shown any greater discrepancy between direct and indirect measurements of pressure than in younger subjects. 21 , 54

Obese patients

It is well known that the accurate estimation of blood pressure using the auscultatory method requires an appropriate match between cuff size and arm diameter. In obese subjects the regular adult cuff (12×23 cm) may seriously overestimate blood pressure. 50 The effect of arm circumference on the cuff method of measuring blood pressure was studied systematically by King. 32

During dynamic exercise the auscultatory method may underestimate systolic pressure by up to l5 mm Hg, whereas during recovery it may be overestimated by 30 mm Hg. 24 , 25 Errors in diastolic pressure are unlikely to be as large, except during the recovery period, when falsely low readings may be recorded. 24 This is the reason why the American Heart Association recommends taking the fourth phase of the Korotkoff sound after exercise. 64

Although the use of mercury sphygmomanometer is regarded as the ‘gold standard’ for office blood pressure measurement, widespread ban in use of mercury devices has diminished their role in hospital settings. Alternative methods such as automated electronic devices have gained increased popularity. The preferred location of measurement is the upper arm, but errors may occur because of changes in the position of the arm. Other technical sources of error include inappropriate cuff size and too rapid deflation of the cuff. Clinic readings may be unrepresentative of the patient’s true blood pressure because of the white coat effect, which is defined as the difference between the clinic readings and the average daytime blood pressure. Patients with elevated clinic pressure and normal daytime pressure are said to have white coat hypertension, which is often explained by state anxiety or conditioned response. There are three commonly used methods for measuring blood pressure for clinical purposes: clinic readings, self-monitoring by the patient at home, and 24-hour ambulatory readings. Self-monitoring is generally carried out using electronic devices that work on the oscillometric technique. Although standard validation protocols exist, many devices on the market have not been tested for accuracy. Such devices can record blood pressure from the upper arm, wrist, or finger, but the arm is preferred. Twenty-four-hour ambulatory monitoring is the best predictor of cardiovascular risk in the individual patient and is the only technique that can describe the diurnal rhythm of blood pressure accurately. Ambulatory monitoring is mainly used for diagnosing hypertension, whereas self-monitoring is used for following the response to treatment. Different techniques of blood pressure measurement may be preferred in certain situations. In infants the ultrasound technique is best, whereas in pregnancy and after exercise the diastolic pressure may be hard to measure using the conventional auscultatory method. In obese subjects it is important to use a cuff of the correct size.

Acknowledgments

This work was supported by Grant No. R01HL078566 from the National Institutes of Health.

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• Published: 06 September 2024

Home blood pressure measurement and hypertension control according to the length of antihypertensive treatment among employees

• Yukako Tatsumi 1 , 2 ,
• Azusa Shima 2 , 3 ,
• Michihiro Satoh 4 , 5 ,
• Ayumi Morino 2 , 3 ,
• Yuichiro Kawatsu 3 ,
• Kei Asayama 1 ,
• Naomi Miyamatsu 2 &
• Takayoshi Ohkubo 1  

Hypertension Research ( 2024 ) Cite this article

Metrics details

This study aimed to investigate the association between the frequency of home blood pressure (HBP) measurement and hypertension control in a middle-aged working population. This study included 627 employees aged 40 years or older who underwent health check-ups for 2 consecutive years from 2019 to 2022 and had blood pressure (BP) ≥ 140/90 mmHg at the health check-up in the first year. The participants were stratified by the length of antihypertensive treatment (within 1 year, >1 year) using data in the first and second years, and were classified by the frequency of HBP measurement (<6 times/week, almost every day) using data in the second year. In each treatment length, logistic regression analyses were used to estimate multivariable adjusted odds ratios (ORs) of controlled hypertension (BP at health check-ups <140/90 mmHg in the second year) in those who measured HBP almost every day compared with those who measured HBP < 6 times/week. The ORs (95% confidence intervals) were 1.56 (0.94–2.73) in those within 1 year of starting treatment and 0.74 (0.44–1.22) in those with more than 1 year of starting treatment. In participants with BP ≥ 160/100 mmHg in the first year, the corresponding ORs were 1.94 (1.04–3.64) and 0.41 (0.13–1.23), respectively. In conclusion, in individuals within 1 year of starting treatment, those who measure HBP almost every day tend to have good control of hypertension. In particular, in those who have BP ≥ 160/100 mmHg before starting antihypertensive medication, measuring HBP almost every day is associated with good control of hypertension.

Among those within 1 year of starting the treatment (Group1) especially in those with blood pressure ≥160/100 mmHg, the frequency of home blood pressure measurement was associated with hypertension control. It was not associated among those with more than 1 year of starting the treatment (Group 2).

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Acknowledgements

We thank all members of Heiwado Health Insurance Society and Heiwado Occupational Health Care Office, especially Ms. Atsuko Kawamura for her careful coordination of the staff who administered the health check-ups and Mr. Shinobu Takada for his contribution to collecting the data. This study was supported by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (21K17313 and 21K19670).

This study was supported by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (21K17313, 21K19670, and 22H03358).

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Department of Hygiene and Public Health, Teikyo University School of Medicine, Tokyo, Japan

Yukako Tatsumi, Kei Asayama & Takayoshi Ohkubo

Department of Clinical Nursing, Shiga University of Medical Science, Shiga, Japan

Yukako Tatsumi, Azusa Shima, Ayumi Morino & Naomi Miyamatsu

Occupational Health Care Office, HEIWADO CO., LTD., Shiga, Japan

Azusa Shima, Ayumi Morino & Yuichiro Kawatsu

Division of Public Health, Hygiene and Epidemiology, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, Sendai, Japan

Michihiro Satoh

Department of Pharmacy, Tohoku Medical and Pharmaceutical University Hospital, Sendai, Japan

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Correspondence to Yukako Tatsumi .

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Three of the authors (AS, AM, and YK) are health professionals of the retail company whose employees are insured by the Employees’ Health Insurance Society. They provided the data for the present study. The other authors do not have any conflict of interest to disclose.

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Tatsumi, Y., Shima, A., Satoh, M. et al. Home blood pressure measurement and hypertension control according to the length of antihypertensive treatment among employees. Hypertens Res (2024). https://doi.org/10.1038/s41440-024-01863-9

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Received : 06 January 2024

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Published : 06 September 2024

DOI : https://doi.org/10.1038/s41440-024-01863-9

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Blood pressure.

Experiment #9 from Engineering Projects with NI LabVIEW and Vernier

Introduction

Blood pressure is a measure of the fluid pressure within the circulatory system. This pressure is required to ensure the delivery of oxygen and nutrients to, and the removal of carbon dioxide and waste products from, tissues. Blood pressure varies from a peak pressure produced by the contraction of the left ventricle, to a low pressure produced by ventricular relaxation. The peak pressure is called systole , and the pressure that is maintained while the left ventricle is relaxing is called diastole . The average pressure is the mean arterial pressure or MAP. Blood pressure is traditionally reported with the systolic pressure stated first and the diastolic pressure stated second. In adults, 120/80 and below is considered normal blood pressure. High blood pressure (also called hypertension ) is a major risk factor for a number of health problems including strokes and congestive heart failure. In adults, 140/90 and above is considered high blood pressure.

In this Project, you will write a LabVIEW program to display the blood pressure of a test subject. You will use a Vernier Blood Pressure Sensor, a non-invasive unit that includes a handheld pump, pressure release valve, and cuff. The cuff is placed on the upper arm to pressurize the arteries, just like other blood pressure monitoring devices. The sensor connects to the cuff and is used to monitor the pressure in the cuff in units of mm Hg. The cuff is pressurized with the pump. The pressure release valve slowly releases pressure out of the cuff. Your front panel design should include a graphical cuff pressure versus time display with a large, easily readable indicator for live cuff pressure readings. You should have the program provide a visual or audible signal when the cuff pressure has reached 160 mm Hg as a signal to stop inflating the cuff. When data collection ends, the VI should use the recorded cuff pressure to calculate and display the test subject’s systolic and diastolic blood pressures.

Sensors and Equipment

This experiment features the following sensors and equipment. Additional equipment may be required.

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This experiment is #9 of Engineering Projects with NI LabVIEW and Vernier . The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.