Your Arm Position Matters for Accurate Blood Pressure Check

By Ibironke Taiwo. BNSc., RN. Freelance Health Writer. Medically reviewed by the DLHA Team.

Elderly black man taking his blood pressure at home.  Image credit: Emily stock from Freepik

Highlights

• Wrong arm position during blood pressure checks will give inaccurate measurements. 

• Inaccurate blood pressure measurements can result in serious consequences. 

• The best arm position for blood pressure measurement is to have the arm at the same level as the heart and supported on a surface such as a table or desk next to the chair that you sit on.

• Blood monitoring devices are a must-have in every home. 

Introduction

Blood pressure is used to describe the force exerted by the blood against the walls of the arteries as it pumps around your body. Blood could be pumped around your body at a normal, lower or higher rates, respectively. 

Blood pressure that is consistently off normal readings has consequences on health generally. Therefore, it is important to know how to measure your blood pressure regularly the right way. 

What You Need to Know About Blood Pressure Measurement 

There are two numbers in the measurement of blood pressure, which are systolic and diastolic. These are important in determining if your blood pressure is normal, high or low. 

Systolic Blood Pressure: This is the number at the top, and it indicates the amount of pressure experienced by the arteries while the heart is beating. 

Diastolic Blood Pressure: This is the number at the bottom, which refers to the amount of pressure in the arteries while the heart is resting. 

Using the blood pressure reading considered normal for every healthy adult, which is 120/80 mm Hg or less. The systolic is 120 mm Hg while the diastolic is 80 mm Hg. These two numbers give important information about your heart health. More attention is placed on the systolic reading as a risk factor for heart disease. 

Low blood pressure is a blood pressure reading below 90/60 mm Hg; it is also referred to as hypotension. Low blood pressure is not usually a problem, as what is considered low blood pressure in one individual might be okay for someone else, although it can give symptoms such as dizziness and fainting in those it is considered as not okay. 

AHA Blood presure categories. Click on image to enlarge.

High blood pressure, also known as hypertension, is a blood pressure reading of 130/90 mmHg and above. High blood pressure does not usually cause symptoms, but it raises your odds for diseases like stroke, heart failure, coronary heart disease, atrial fibrillation (excessively rapid beating of a part of the heart), chronic kidney disease, and peripheral arterial disease.

There are two major ways to measure blood pressure, the direct and indirect methods. The direct method involves the use of a special tube that is inserted directly into an artery (blood vessel) in your body to obtain a measurement. This method is mostly used in the intensive care unit and in the operating room. 

The indirect method involves the use of an external cuff (band) that is wrapped around your arm to collapse the artery in your arm, and using a manual or automated measuring device to measure the blood pressure when the collapsing cuff is released. During the use of the manual method, a stethoscope is used to listen to the blood flow and pulse as the cuff inflates and deflates, while in the automated method, the device automatically inflates, deflates, and measures the blood pressure. 

Why Does Arm Position Matter When Checking Blood Pressure? 

Some arm positions commonly used to take blood pressure readings may produce inaccurate readings, which could in turn lead to false blood pressure measurements. 

In most cases, blood pressure is measured with the arm positioned in one of these three ways: the arm supported on a desk, the arm supported on the patient's lap, or the arm hanging at the patient's side without any support. Which of these arm positions is appropriate? 

Research has shown that an arm supported on the laps while taking blood pressure measurement results in an overestimated systolic blood pressure by about 4 mmHg over the normal value for the patient, while those who position their arms without any support will have an overestimated systolic blood pressure by almost 7 mmHg. 

This is because the blood vessel in the arm is at the greatest vertical distance from the heart when the arm is either on the lap or at the side unsupported. Gravity increases the pressure in these blood vessels and also makes it harder for the blood to return to the heart when the arm is lower than the heart. This leads to a higher blood pressure reading. 

The best arm position for blood pressure measurement is to have the arm supported on a surface such as a table or desk next to the chair. In this position, the arm is at the same level with the heart. 

What Happens When Blood Pressure is not Measured Properly? 

Inaccurate blood pressure measurement and reading can result in lots of complications and serious consequences, some of which include: 

• Incorrect diagnosis and treatment: A reading higher than the normal may be diagnosed as hypertension.

• The wrong use of medication: A patient who has been misdiagnosed as having hypertension will definitely be given medications to control it and be exposed to the side effects that come with the drugs. 

• A reading lower than your actual blood pressure can give a false sense of security, making you assume to be healthier than you are. 

• Untreated high blood pressure can increase the risk of fatal strokes and heart attacks. 

Tips for Accurate Blood Pressure Measurement 

Irrespective of where you are getting your blood pressure checked, certain guidelines need to be followed to ensure that an accurate measurement is obtained. These include: 

• Place your hand at a horizontal level, for instance, on a desk or table next to a chair.

• Do not eat, drink, exercise, or use tobacco 30 minutes before you take your blood pressure. 

• Before taking your blood pressure reading, make sure that your bladder is emptied, as a full bladder can temporarily increase blood pressure. 

• Sit in a comfortable chair supporting your back.

• Keep your feet flat on the ground. 

• Make sure the blood pressure cuff is secured firmly on the arm but not too tight. 

• The cuff should be placed on bare skin directly above the bend of your elbow and not over a cloth. 

• Do not talk while measuring blood pressure. 

• Take a couple of readings at 1–3-minute intervals. 

Devices You Can Use to Monitor Your Blood Pressure 

Blood pressure monitoring devices are tools used to measure your blood pressure at home or in the hospital. These devices measure the force of blood against the walls of your arteries, with which they are able to diagnose conditions like hypertension. It is essential that every household have a blood pressure device in their homes for the sole purpose of early diagnosis and intervention.  

There are various types of blood pressure monitoring devices. See figure 1 below

Different types of blood pressure measuring devices. Click on image to enlarge.

1. Manual Monitors: There are two types of manual monitoring devices, which are the mercury sphygmomanometer and the aneroid sphygmomanometer.  

•    Mercury sphygmomanometers: This is usually considered the gold standard for accuracy but requires professional handling, and it is the most commonly used device for checking blood pressure. It has a graded tube containing mercury that measures the pressure applied by the bladder of the inflatable rubber cuff on the upper arm. It is placed on a table for accurate measurement. 

•  Aneroid Monitors: This does not require the use of mercury or any fluid for measurement. In this device, the stethoscope is directly attached to the cuff, which in turn is attached to a gauge with a dial. 

2. Digital Monitors: These devices measure blood pressure electronically. The cuff is directly connected to the device, and after pressing the switch button, the device inflates and deflates by itself and displays the readings. 

These devices are usually portable and can be moved from one place to another. Suitable for home use. 

Conclusion 

Ensuring accurate blood pressure measurements is essential for effective diagnosis and management of blood pressure disorders. By being mindful of how the arm is positioned and supported - ideally at heart level - can significantly enhance the reliability of blood pressure checks and improve health outcomes. Always consult with healthcare professionals to improve your technique and ensure that your measurements contribute positively to your health management plan.

Sources:

1. Taiwo I. The correct way to take your blood pressure at home. [Internet]. Datelinehealth Africa. Last updated June 29, 2024. Accessed December 14, 2024. Available from here.

2. Bello A. Hypertension in Nigerian Adults: Essential Things to Know. [Internet]. Datelinehealth Africa. Published March 20, 2023. Accessed December 14, 2024. Available from here.

3. Textbook. Sphygmomanometer: Learn its definition, types, parts, and working principles. [Internet] Last updated Dec. 8, 2023. Accessed December 14, 2024. Available from here.

4. Liu H, Zhao D, Sabit A, et al. Arm Position and Blood Pressure Readings: The ARMS Crossover Randomized Clinical Trial. JAMA Intern Med. 2024;184(12):1436–1442. doi:10.1001/jamainternmed.2024.5213. Abstract available from here.

Related: 

• The correct way to take your blood pressure at home

• Hypertension in Nigerian Adults: Essential things to know

Published: December 29, 2024

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