24-Hour Ambulatory Blood Pressure Monitoring

What is ambulatory blood pressure monitoring?

Ambulatory blood pressure monitoring is a way of measuring and managing high blood pressure. High blood pressure (hypertension) means your top number (systolic blood pressure) is at least 130 mmHg (millimeters of mercury), and/or your bottom number (diastolic blood pressure) is at least 80 mmHg.

Ambulatory blood pressure monitoring records your blood pressure (BP) readings over a 24-hour period, whether you’re awake or asleep. This happens outside your healthcare provider’s office, as you go about your daily life. You wear a cuff on your arm and a small device attached to a strap or belt.

You may be more familiar with having your BP checked in a healthcare provider’s office during an appointment. In this case, your provider uses a device called a sphygmomanometer to measure and record one or two readings during your visit.

Ambulatory blood pressure monitoring takes dozens of readings over a continuous period. In most cases, the device records readings every 15 to 30 minutes during the day and every 60 minutes at night. The device also measures your heart rate (how fast your heart is beating). Your provider uses this data to calculate your average BP over the 24-hour period. They also calculate changes in BP and heart rate, BP distribution pattern and other statistics.

Why is ambulatory blood pressure monitoring used?

Healthcare providers use this method for many reasons, including to:

• Confirm a diagnosis of hypertension.
• Identify how changes in your blood pressure relate to your daily activities and sleep patterns. Usually, your systolic BP (your top number) decreases about 10% to 20% when you sleep. However, this isn’t always the case. Your systolic BP may stay the same or go up.
• See how well your blood pressure medication is controlling your high BP. Your medication may not control your BP throughout the entire day and night. Your provider may need to adjust your dosage or the times that you take your pills, depending on your BP patterns. Or, you may need more than one drug to stabilize your BP.
• Identify changes in your blood pressure readings at your healthcare provider’s office versus at home. These changes can help show your level of risk for cardiovascular disease.

Ambulatory blood pressure monitoring can detect abnormal changes in BP that might otherwise go unnoticed. It’s a useful way to detect different blood pressure patterns, as listed below.

White coat hypertension

Some people who have normal blood pressure at home have elevated blood pressure in a healthcare setting. This is known as white coat hypertension, or white coat syndrome. It can lead to a hypertension diagnosis when your blood pressure is actually normal. White coat hypertension occurs in 10% to 30% of people with elevated BP readings in healthcare settings.

Current guidelines don’t recommend treatment when ambulatory monitoring shows normal readings outside your provider’s office. However, research continues to explore this topic. White coat hypertension may still indicate a blood pressure problem. So, you and your provider should keep an eye on it.

Sustained hypertension

This refers to BP readings that are elevated whether you’re in your provider’s office or at home. Researchers have linked this condition to an increased risk of heart and kidney damage, as well as stroke.

Masked hypertension

This occurs when your BP reading is normal at your provider’s office, but elevated when you’re at home. It may affect up to 30% of adults who have normal BP readings at their provider’s office. You may face a higher risk of developing masked hypertension if you have kidney disease, diabetes or obstructive sleep apnea.

Nocturnal hypertension

This means your BP goes up when you sleep. Nocturnal hypertension affects at least 2 in 10 white people, and about 4 in 10 Black people. It’s more common among people who have diabetes or kidney disease. Research continues to explore how nocturnal high BP relates to cardiovascular disease.

Who needs ambulatory blood pressure monitoring?

Ambulatory blood pressure monitoring can help a wide range of people. Your healthcare provider may recommend ambulatory blood pressure monitoring if you:

• Have high blood pressure based on readings at your provider’s office, but you haven’t yet started treatment.
• Need changes to your blood pressure medications.
• Still have high blood pressure despite medications.
• Are taking other medications that may affect your blood pressure.
• Have fainting episodes or hypotension (low blood pressure).
• Have high blood pressure during pregnancy.

Are ambulatory blood pressure monitors accurate?

Yes. Ambulatory blood pressure monitoring is an accurate and effective way to measure your blood pressure. It gives your healthcare provider better data compared with only measuring your BP at your medical appointments.

Ambulatory blood pressure monitoring provides frequent readings of your blood pressure and heart rate over a 24-hour period.

How do I prepare for ambulatory blood pressure monitoring?

Your healthcare provider will tell you how to prepare. Some general tips include:

• Choose a 24-hour period that best represents your normal routine. This may mean choosing a weekday rather than a weekend.
• Plan to keep a journal of what you do during the 24-hour period. This includes when you wake up and go to bed, when you take any medications and when you eat. You should also record any symptoms you experience (like dizziness or shortness of breath).

Preparation also involves knowing in advance what you need to avoid. During your 24-hour period, you shouldn’t:

• Engage in strenuous physical activity.
• Shower or swim.
• Remove any part of the device without first asking your provider.

How is ambulatory blood pressure monitoring done?

Ambulatory blood pressure monitoring happens outside of your healthcare provider’s office. But to get things started, you meet with your provider for an appointment. This is when you receive your equipment and instructions for the 24-hour period.

Here’s what happens at your appointment:

• You receive your equipment. This includes a small device that’s about the same size as a portable radio. You wear this on a belt or strap. You also have a BP cuff around your arm. Tubing connects the cuff to the device.
• Your provider fits the cuff on your arm and sets up your device. Once everything is properly fitted, your provider begins recording data.
• You receive instructions. Your provider gives you detailed instructions that you should closely follow. Be sure to ask any questions you might have before you leave your provider’s office. When you leave, the equipment stays on you. Your provider will tell you what time to remove it and when to bring it back.

Here’s what happens once you’re home:

• Your arm cuff inflates at certain intervals. This may be every 15 to 30 minutes during the day, and every 60 minutes at night. Inflation means the device is measuring your BP. You may feel the cuff squeezing your arm. This is brief. Keep your arm still during these moments to get the most accurate measurements.
• You may have disrupted sleep. You may wake up periodically when the device begins measuring your BP. This is normal. But try your best to ignore the sensation and get back to sleep.
• You follow your normal routine. Do what you normally do, but avoid bathing or swimming. Also, avoid heavy exercise. Keep a journal as your provider instructs.
• You take your medications as your provider directs. Ask your provider whether or not you should continue your medications while ambulatory blood pressure measurement is in progress. Follow their guidance closely.

How do you sleep with an ambulatory blood pressure monitor?

You may have trouble sleeping, and that’s understandable. You’re not used to having a cuff on your arm when you sleep. But try your best to relax. Do whatever you can to make the rest of your sleep environment comfortable. You may want to:

• Play soothing music.
• Cover your windows to block out any strong light.
• Set your thermostat to a temperature that’s comfortable for you (not too warm or too cold).

Your provider will tell you how you may adjust your equipment while you sleep. For example, you may be able to remove the strap from your body and place it next to your pillow. Only do this if your provider says it’s OK. You shouldn’t remove the arm cuff until the end of your monitoring period.

Talk to your provider about what you can do to get the best quality sleep.

What are the benefits of ambulatory blood pressure monitoring?

Ambulatory blood pressure monitoring is an incredibly useful clinical tool that can help you receive the most appropriate care. Among its many benefits, this form of BP monitoring can:

• Accurately measure your blood pressure. This method measures your BP throughout the day rather than just at one or two time points. This is an accurate way to measure your BP and its patterns since your BP normally changes based on time of day and what you’re doing at any given moment.
• Rule out white coat syndrome. If your BP is raised only at your provider’s office, you have white coat syndrome. Learning this is the case can prevent you from taking unnecessary medications.
• Detect masked hypertension. If your BP is low at your provider’s office but high at other times, your typical BP is “masked” (hidden). This cardiovascular disease risk factor would otherwise go unnoticed. In this case, your provider may prescribe medications to lower your BP and lower your risk of stroke and other complications.
• Guide your treatment plan. This monitoring can help evaluate your response to long-acting hypertensive medications. Your provider can adjust your treatment plan as needed.

What are the disadvantages?

This method of BP monitoring, though noninvasive, may still be uncomfortable for some people. Disadvantages include:

• Arm soreness. Pressure due to repeated inflation of the cuff may make your upper arm sore.
• Sleep disruption. BP readings during the night may interfere with your sleep.
• Skin irritation. The cuff may irritate your skin and cause a mild rash that usually goes away on its own.
• Possible cost. Some insurance providers only reimburse you for ambulatory devices in specific cases. These include if your provider suspects you have white coat syndrome or masked hypertension. Talk to your provider about what costs you may expect.

What type of results do I get and what do they mean?

Your healthcare provider will transfer the data from the device to a computer, which analyzes your BP readings. Your provider will talk to you about your results and what they mean for you.

Some results your provider may discuss with you include:

• 24-hour average blood pressure. This is your average BP reading from the entire monitoring period.
• Daytime blood pressure. This is your typical BP during the hours you’re awake
• Nighttime blood pressure. This is your typical BP during the hours you’re asleep.
• Nocturnal dipping patterns. This is the difference between your daytime and nighttime BP readings. Your nighttime reading should be lower.

What is a good ambulatory blood pressure?

These are the normal readings for ambulatory blood pressure monitoring:

• 24-hour average: At or below 125/75 mmHg.
• Daytime BP: At or below 130/80 mmHg.
• Nighttime BP: 110/65 mmHg.
• Nocturnal dipping patterns: 10% to 20% drop in BP.

Your provider will tell you when you can expect to see your results. They’ll also discuss the results with you and discuss any next steps, like medication changes.

When should I call my doctor?

As you complete your 24-hour monitoring, call your healthcare provider if you:

• Experience any technical problems with the device.
• Have any questions about what you should do or avoid doing during the monitoring period.

A note from Cleveland Clinic

No matter how many times you tell yourself to calm down, you might still feel anxious when your provider puts a blood pressure cuff on your arm. That’s a common reaction, and it can be hard to actually relax. If that’s the case, ambulatory blood pressure monitoring can help. The device checks your BP as you go about your normal routine. It can show whether or not raised BP numbers at your provider’s office reflect what’s usually happening in your body.

Besides diagnosing white coat syndrome, this method can also help your provider diagnose and treat a range of other BP problems. Talk to your provider about how ambulatory blood pressure monitoring can help you, and what you can learn from the results.