Picture the last time your doctor checked your blood pressure. Were you sitting in a chair? Were you relaxed? Were you silent? Did your doctor or nurse take more than one reading?
Chances are, the answer to one or more of these questions is “no” — which means there’s a good probability your blood pressure reading was wrong.
Blood pressure measurement is one of the most common and high-stakes tests in medicine. Getting it right can be a matter of life or death because high blood pressure leads to serious diseases like heart attacks, strokes, erectile dysfunction, even dementia. More than 1,100 people in the US die each day from diseases caused by high blood pressure, and one in five adults don’t know they have it. A faulty reading can mean not catching an early warning sign.
The American College of Cardiology and American Heart Association have guidelines with steps that health professionals are supposed to follow to get accurate measurements. But they are notoriously bad at sticking to them.
“We wouldn’t fly on a plane where the pilot said, ‘I’m going to ignore the guidelines I have for safe travel,” said Dr. Paul Whelton, a professor at Tulane University and chair of the writing committee for updated US guidelines on blood pressure. “But that’s exactly the situation we have today with respect to blood pressure measurement.”
The only way to know whether you have high blood pressure is by getting an accurate reading. Yet the current data suggests only half of people with high blood pressure in the United States are able to get their blood pressure under safe limits, in part because improper measurement of blood pressure leads to the wrong diagnosis.
That’s why US blood pressure guidelines were recently updated for the first time in 14 years. Among other changes, the guidelines double down on correct blood pressure measuring technique, recommend the use of automated blood pressure machines, and suggest measurements outside of the doctor’s office — all in the hopes of saving lives. It’s a significant moment in what’s now an international movement to take blood pressure more seriously.
There is reason for hope that health professionals in the US can do better. Just look to Canada, which now has the largest proportion of hypertensive patients with their blood pressure under control in the world. It wasn’t always that way — but the fact that they got there suggests other doctors and patients can too.
High blood pressure, explained
Blood pressure is the force that blood exerts on your arteries. With every contraction and relaxation of your heart, the pressure inside your arteries spikes (called systolic blood pressure) and then drops (diastolic blood pressure). A normal blood pressure range is less than 120 mmHg systolic and less than 80 mmHg diastolic — or less than “120 over 80.”
Blood pressure varies from hour-to-hour, day-to-day, and year-to-year. But stubbornly high blood pressure becomes dangerous because it can cause arteries to burst, get inflamed, or clog, leading to diseases like heart attacks, strokes, and heart failure.
Many factors come together to cause high blood pressure, some of which you can control and some you can’t. Age, sex, ethnicity, and other health conditions can all affect your risk of high blood pressure — but you can’t change them.
Physical activity, a diet with less salt and more vegetables, not smoking, and maintaining a healthy body weight though can all bring blood pressure down. So can medications in some cases.
Although cardiovascular diseases, like heart attacks and strokes, are still the No. 1 cause of death in the United States, they have drastically declined since the 1960s. This is thanks to public health officials targeting behaviors that are linked to developing these illnesses, including smoking, alcohol use, and eating trans fat. But there has been less success with reducing high blood pressure, a key risk factor for heart attacks and strokes.
Why doctors often fail to take correct blood pressure readings
There’s a whole slew of things health professionals are supposed to do to get accurate blood pressure readings, many of which are performed correctly: placing the cuff at the right location around your arm, holding your arm at the level of your heart, using a stethoscope to listen to the pulse, and making sure there is no clothing on your arm.
But other steps that require more time often get overlooked. These include making sure that you sit in a chair and relax for at least five minutes before the measurement, that you have an empty bladder, and repeating the process for a second measurement one or two minutes later.
Whelton thinks one big reason physicians haven’t done a good job of measuring blood pressure is that they are “stretched in many directions” and not incentivized to aim for precision. “So I don’t think there is anything malicious about it, but [doctors wrongly] assume, in many instances, they’re doing a great job,” Whelton said.
In my own experience as a medical student, I’ve noticed that taking blood pressure correctly is indeed a luxury of time — and despite their best intentions, overworked doctors are often too crunched and too distracted to bother with correct technique.
When researchers have compared the blood pressure readings that doctors record to the values obtained by nurses who are specifically trained to follow correct technique, the results are alarming. Casual measurements taken by doctors overestimate blood pressure by about 10 mmHg. That could be the difference between normal blood pressure (120 mmHg) and stage one hypertension (130 mmHg), according to newly updated US definitions.
How to take a correct blood pressure reading, according to the new, controversial guidelines
In hopes of finally changing the status quo — and reducing cardiovascular diseases — 2017 guidelines, published by the American College of Cardiology and the American Heart Association (in conjunction with nine other groups), just broadened the definition of hypertension.
For the first time ever, hypertension is now diagnosed at systolic blood pressures of 130 mmHg or higher, rather than 140 mmHg. This change means that an additional 31 million adults in the US are now considered hypertensive, and 4 million of these people qualify for medication to lower their blood pressure.
This also means accurate blood pressure measurement is more important than ever to identify and treat those at risk. To address this, the guidelines for doctors are clear: They recommend using automated blood pressure devices (rather than manual hand pump sphygmomanometers), averaging multiple readings, and measuring blood pressure outside of the clinic (“out-of-office” measurements), which, for most patients, can help increase the accuracy of blood pressure readings.
But most important is following correct technique when measuring blood pressure using a manual blood pressure device, for which the new US guidelines include a nearly 19-step checklist. Here are some of the other checklist items to follow before your doctor or nurse takes your blood pressure:
- Sit in a chair with your feet on the floor for at least five minutes (sitting on the exam bed does not count) before the reading
- Avoid caffeine, exercise, and smoking for 30 minutes before the measurement
- Make sure your bladder is empty
- Don’t talk during the measurement
- A pressure reading initially should be taken in both arms, and future readings should be taken from the arm with the higher reading
For many years, blood pressure guidelines have recommended an average of two or more blood pressure readings on two or more occasions to get a correct measurement. They “underscored that recommendation” in the new guidelines, Whelton said.
Canada led the way with better methods of measuring blood pressure
Just because the blood pressure status quo hasn’t been improving lately doesn’t mean it won’t — and the Canadian example is instructive here.
In the 1980s and early 1990s, Canada was far behind the US in terms of properly diagnosing and managing hypertension. During that time, only 13 percent of Canadians with hypertension reached their blood pressure target, while this number was 25 percent in the US. Today, Canada is recognized as the world leader in lowering blood pressure, with 68 percent of hypertensive patients who have their blood pressure under control. (Today, about half of Americans have their hypertension controlled.)
While there are many differences between Canada and the US that could account for this gap, it’s worth noting that Canada embraced alternative forms of blood pressure measurement early on, like taking measurements outside of the doctor’s office with automated devices.
“Canada was one of the first [countries] to recommend out-of-office blood pressure measures,” said Dr. Nadia Khan, president of Hypertension Canada, the not-for-profit group responsible for blood pressure guidelines in Canada. “Out-of-office measures are much better at predicting future cardiovascular events than office blood pressures.”
The new US guidelines say much the same, which is one reason why, Khan remarked, the US is “moving closer to the Canadian approach.”
So the next time you head to the doctor’s office, it might be worth asking for a repeat measurement, a chair to sit on, or for your doctor to use a validated automated blood pressure monitor. Your life may depend on it.
Dylan Collins is a medical student at the University of British Columbia, and holds a PhD from Oxford University where he was a Rhodes Scholar. You can find him on Twitter @DylanRJCollins.