By Dr Joe
Are wrist blood pressure monitors accurate? This is a question that I set about answering some years ago. Not out of medical research curiousity but as a patient myself.
Apart from knowing the answer to the accuracy of wrist monitors, I also explain why my answer is what it is and finally I’ll tell you if I recommend wrist BP monitors as a home blood pressure monitoring kit or not. That’s what you are going to get on this page.
Keep reading:
Being a doctor and someone who suffers from high blood pressure, I accidentally found the answer to the question: are wrist monitors accurate for blood pressure; more out of luck rather than by design.
It’s a long story. Well kind of.
I have told the story here when I wrote about the pros and cons of wrist blood pressure monitors.
So, are wrist blood pressure monitors accurate?
My curious search for an alternative to upper arm blood pressure monitor led me to discover the truth about wrist blood pressure monitors. The long and short of my short adventure was that the wrist blood pressure monitors are not accurate.
So, if you want to know the real answer to the question: are wrist blood pressure monitors measurements accurate? The answer is; No, wrist monitors are not accurate for blood pressure measurement.
My claim is based on my personal experience of 4 different brand of wrist monitors. These wrist monitors kept giving wild blood pressure readings. Usually BP readings that would suggest I am about to have a stroke or heart attack.
With doubts in my mind as to such ridiculously high readings, I had to do a validation of the readings. Fortunately I had an upper arm monitor at home.
When I checked my blood pressure with my upper arm monitor at the same time as the wrist monitor, I had normal blood pressure.
So, whereas the wrist monitor was producing BP readings that would suggest I needed to go to ER (A&E) immediately for medical attention, my upper arm monitor was giving readings that were perfectly normal.
The contrast between the wrist monitor and the upper arm monitor was as clear as the Biblical ‘Red Sea parting for Moses and his troops to go through’.
When you have recurrent episodes of false readings with different brands, it is not unreasonable to reach that conclusion that wrist monitors are not accurate for blood pressure measurements.
Mind you on each occasion, I validated with the upper arm monitor. Occasionally, there was a close match of the readings from the wrist monitor and the upper arm one.
But these episodes of the close match were very few and far between. Scenarios like that meant I had to reach that conclusion, that the wrist monitors were inaccurate and therefore unreliable.
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Why are wrist blood pressure monitors not accurate for Blood pressure reading?
Okay I won’t just make a statement like that and not give you reasons for why wrist blood pressure monitors are not as effective as upper arm monitors.
One reason for this inaccuracy of blood pressure readings from the wrist monitors is the blood vessel from which the wrist monitor is getting its reading from.
The wrist monitor measures the pressure in the Radial artery whereas the upper arm monitor measures the pressure in the Brachial artery.
Our body’s arterial tree is a high pressure system. But the walls of our arteries have been cleverly designed by nature to maintain a pressure gradient that drives blood onwards and forwards downstream.
This means smaller vessels are more muscular than larger vessels. Larger vessels closer to the heart are lot more elastic than smaller vessels downstream. The larger vessels have to be elastic to withstand the high pumping pressure of the heart ventricles.
- Larger vessels – elastic
- Smaller vessels – muscular
The brachial artery is larger than the radial artery. Meaning the brachial artery is more elastic than the radial artery. The smaller arteries will have a higher resistance i.e pressure, within them than the larger blood vessels because they are more muscular.
This differential pressure is necessary for the continuous flow of blood within the arterial tree. That’s the concept of the physics of flow through vessels of different sizes.
But of course nature is very clever, you have a sudden drop in pressure when blood arrives at the very small arteries called the arterioles. This is designed to protect us from harm and keep the delivery of nutrients and oxygen efficient.
I am digressing here for good reason but the video below explains it a little bit more about the physiology.
The point I am making is that; you will more than likely get higher blood pressure readings in the smaller radial artery (that the wrist monitors measures) than the larger brachial artery (that the upper arm monitor measures).
The second reason wrist monitors give inexact readings is that they are very sensitive to positioning. Any slight adjustment of your wrist position will lead to swings in blood pressure readings.
Which brings me nicely to the third reason for wrist blood pressure monitors inaccuracy. We advise high blood pressure patients to measure their blood pressure by placing the cuffed area to the level of the heart.
Now imagine trying to place the cuffed wrist at the level of the heart. It’s not a natural position for the wrist. That causes all sorts of positional problems.
Compared to the upper arm, which is almost at the level of the heart requiring just a little elevation, the wrist monitor will need a higher elevation. That’s a recipe for errors in blood pressure readings.
Would I recommend Wrist blood pressure monitors?
The short answer to that question is: No, I won’t.
The American College of Cardiology and the American Heart Association are in favour of home blood pressure monitoring. Just like me, both organisations do not recommend the use of wrist blood pressure monitors.
They both recommend the upper arm monitors and I support the recommendation as well.
Why is this?
For the same reasons that I have outlined earlier on this article. It is clear. The wrist blood pressure monitor readings are not accurate. If you want to monitor your blood pressure at home, you’d want to use a device that is reliable.
You would use a blood pressure measurement device that produces clear, unambiguous blood pressure readings every time. Not some of the time but every time.
The wrist monitors cannot be trusted to do that. The wrist blood pressure monitors are not effective home BP monitoring kit.
The last thing you want is showing results of blood pressure readings to your doctor that are ambiguous and inaccurate. Situations like that will lead to your doctor making wrong management decisions.
You don’t want that. In fact, it could be downright dangerous. Avoid!
Suggested further reading:
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Dr. Joe