Are you doing it all wrong? Last week, US researchers reported that keeping your arm in the wrong position when taking blood pressure could substantially overestimate the reading.
As a result, many people could be misdiagnosed with hypertension.
So what is the correct way? I’ll get to that.
Taking blood pressure is a low-tech medical measure, but the results can make the difference between life or death.
But first, you may be wondering why, in this era of high-tech scans and tests, we take this low-tech measure (putting a bracelet around your arm and tightening it tightly) so seriously.
The fact is, it could be a matter of life or death. The first number in your reading, known as systolic pressure, reflects the pressure in the blood vessels when the heart contracts: the maximum pressure. The second number, the diastolic, is when the heart relaxes. A healthy reading is around 120/60 mmHg.
When blood pressure is higher, you can expect blood flow to be faster, like when you turn on the garden hose. In fact, it is slower; This is because blood is a “liquid” tissue, a fluid with tiny particles like blood cells, and higher pressure tends to cause slower flow.
High blood pressure is a sign of diseased arteries. Arteries have elastic walls and can expand or contract to change diameter. If they are not flexible, the work of the heart to pump blood increases. The result? A weaker heart as the muscle becomes progressively damaged, leading to heart failure, blood clots, heart attacks and strokes.
A reading above 140/90 used to be the cut-off point for diagnosing hypertension, but today it is thought that the limit should be lower: 120-130 systolic, 60-70 diastolic. My opinion is that, like body weight, blood pressure is something that everyone over 30 should have checked regularly, maybe once a month.
The good thing is that you don’t need fancy technology to measure blood pressure. You can get a simple, accurate monitor, known as a sphygmomanometer, for around £20.
But as this latest study has confirmed, it must be used correctly.
Choose a device with an upper arm cuff; I would avoid the ones that go around the wrist or finger, as the reading will not be as accurate. The goal is to record the pressure in a large blood vessel, which will be very similar to the pressure in the main artery, the aorta, as it leaves the heart. The brachial artery in the upper arm is about the diameter of a pencil and, in my opinion, is the only place to measure blood pressure.
The cuff is pumped to compress the artery and close it. The pressure is then automatically reduced and, at the moment when the blood can spurt out, a small sound is made that is detected by a microphone in the cuff. That is the systolic blood pressure. Diastolic is when, as the cuff pressure is slowly reduced, the blood pulses again with each heartbeat.
The handcuffs supplied are standard size, but if you have a large arm (whether you are overweight or muscular) you will need to purchase a larger one. Using a small cuff on a large arm makes it much harder to close the artery, so the reading will be much higher than your actual blood pressure since what you are getting is distorted by the extra work of the cuff.
Dr. Scurr recommends a number of steps before taking your blood pressure to ensure an accurate reading, including going to the bathroom, as a full bladder can increase the result by up to 10 percent.
The best time to take your blood pressure is first thing in the morning or late at night.
But whatever time you do it, refrain from drinking too much coffee, smoking, drinking alcohol, or doing any exercise (even just riding your bike home or walking up several flights of stairs) at least 20 to 30 minutes beforehand. All of these can temporarily raise blood pressure (putting pressure on the entire cardiovascular system), producing a false reading. Also go to the bathroom and empty your bladder; If you’re eager to go, your blood pressure can rise at least 10 percent.
Then sit in a quiet space, without interruptions, for five minutes.
Place your forearm on the arm of the chair or on a table, about the height of your heart (this is due to the physics of blood flow, but essentially makes it more precise).
The bottom of the cuff, around your bare upper arm, should be a couple of fingers above the crease of your elbow, ensuring the microphone is over your brachial artery. The bracelet should also be loose enough to allow a finger to slip between it and your arm. Then press the start button on the blood pressure monitor.
If the pressure seems high, much above 140/90, wait a few minutes and take it again.
If it stays high, take a couple of readings two or three times a week for several weeks, at different times of the day, say when you first wake up, sometime around midday, and before going to bed.
The distribution of readings is important, and it will be useful to take an average: consistently high readings demand the attention of a GP, as high blood pressure can quietly cause damage, becoming irreversible and dangerous.
That’s why I urge my patients to get a blood pressure monitor and use it. It is no less important than having a scale to monitor your weight if you want to survive.