Ambulatory blood pressure monitoring (ABPM) at Cardiff and Vale Hospitals

What is ambulatory blood pressure monitoring?

Ambulatory blood pressure monitoring (ABPM) checks your blood pressure automatically at regular intervals over 24 hours, as you go about your normal day and night. You wear a cuff around your upper arm, connected to a small recording device on a belt or strap, which takes and stores each reading by itself.

Why might I need ambulatory blood pressure monitoring?

Your doctor may ask you to have ABPM if a clinic blood pressure check suggested you might have high blood pressure (hypertension), so they can see your true blood pressure over 24 hours rather than from a single reading. It's considered the most accurate way of confirming a diagnosis of hypertension. ABPM may be recommended to:

• confirm whether you have high blood pressure, especially if your clinic readings have been raised
• check whether your blood pressure is only raised at the doctor's surgery or clinic, known as white coat hypertension
• see whether blood pressure medication needs to be started, changed or adjusted
• investigate blood pressure that's been difficult to control, or symptoms such as fainting or dizziness
• monitor your blood pressure during pregnancy, if your care team is checking for high blood pressure.

What are the benefits of ambulatory blood pressure monitoring?

• It gives a clear picture of how your blood pressure changes over a full day and night, rather than a single reading
• It can rule out white coat hypertension, where your blood pressure rises only because you're anxious about being tested by a doctor or nurse, which can prevent unnecessary treatment
• It can detect masked hypertension, where your reading is normal at the clinic but raised the rest of the time, so it doesn't go unnoticed
• It's considered the most accurate way to confirm a diagnosis of hypertension, and can help guide changes to your treatment.

Are there different types of ambulatory blood pressure monitoring?

Most ABPM devices use a cuff around the upper arm, connected to a small monitor that inflates the cuff and records the pressure automatically. If ABPM isn't suitable for you, or you're unable to tolerate it, your doctor might suggest home blood pressure monitoring instead, where you check your own blood pressure at set times using a home machine.

How do I prepare for ambulatory blood pressure monitoring?

You'll usually visit a clinic first to have the monitor fitted and explained to you. Before your appointment:

• wear loose clothing with sleeves that are wide enough for a cuff to fit underneath and inflate comfortably
• choose, if you can, a normal 24-hour period that reflects your usual routine, rather than an unusually busy or restful day
• you may be asked to keep a record of when you wake up, go to sleep and take medication, as well as what you are doing when a reading happens.

What happens during ambulatory blood pressure monitoring?

Here's what typically happens:

1. A nurse or health professional fits the cuff around your upper arm and connects it to the recording device, which you wear on a belt or strap.
2. They start the monitor and explain how it works, including what to do when it's about to take a reading and how long you'll need to wear it – usually 24 hours.
3. You go home and carry on with your normal routine. The cuff automatically inflates roughly every 30 minutes during the day and every 60 minutes at night.
4. Just before each reading, you should sit down if you can, keep your arm still and at the level of your heart, and avoid talking or crossing your legs.
5. You may feel a tingling or squeezing sensation in your arm while the cuff inflates. This passes once the cuff deflates.
6. After 24 hours, or as instructed, you remove the equipment yourself or return to have it removed, so the readings can be downloaded and analysed.

What happens after ambulatory blood pressure monitoring?

The recorded data is downloaded onto a computer and analysed. This usually shows your average blood pressure over the full 24 hours, plus separate averages for daytime and night-time, since blood pressure normally drops by about 10 to 20% overnight compared with when you're awake, a pattern known as dipping.

Your doctor will discuss the results with you, usually at your next clinic appointment, though sometimes a letter is sent to your GP instead.

What are the risks or side effects of ambulatory blood pressure monitoring?

ABPM may not be suitable for everyone. It's generally avoided if you have a severe blood clotting disorder, a serious irregular heart rhythm such as atrial fibrillation, or an allergy to latex, which is sometimes used in the equipment.

Possible side effects include:

• a tingling or squeezing sensation in your arm while the cuff inflates, which passes once it deflates
• mild arm discomfort from repeated inflation of the cuff over 24 hours, but this should be temporary
• disrupted sleep, since the cuff can wake you when it takes a night-time reading
• mild skin irritation or a rash where the cuff sits, which usually clears up on its own.