Home blood pressure monitors (BPM) have changed the way millions of patients deal with COPD or Hypertension. Considering that you use an FDA-cleared device from a reputable brand, the readings should be accurate and reliable. Somehow, automatic blood pressure monitors can sometimes inflate twice and even reach a level of inflation that can become painful.
In this article, we will explain why you may feel that your precious device is acting weird. In most cases, the issues will be easy to resolve. But first, let dig a little bit into the technology and principles at the core of automated blood pressure devices.
How do automatic Blood Pressure Monitors work?
Check the video below to understand the fundamental principles underlying arterial pressure and systolic and diastolic blood pressure.
In a nutshell, systolic blood pressure (the higher number) measures the pressure (in mm of mercury) of the blood flow against the walls of the arteries when the heart beats. Diastolic blood pressure (the lower number) does just the opposite. It is the pressure of the blood between heartbeats when the heart is at rest.
In a study published in 2017, Researchers showed that automatic blood pressure measures were not as accurate as manual ones, especially in ICU settings. Nevertheless, the American Heart Association recommends using automatic Blood Pressure Monitoring devices to monitor your blood pressure at home as long as they are validated and the FDA cleared.
Automatic BPMs do not directly measure the systolic and diastolic pressures. Pressure sensors will detect the maximum oscillation of the blood flow against the walls of the arteries, called the Mean Arterial Pressure or MAP for short. The values will be extrapolated using the internal software of the device.
With such precise sensors, automatic BPM can sometimes provide inaccurate readings, become painful or even inflate twice due to three main reasons:
- Wrong sized cuff,
- Cuff not properlly located,
- Arm not adequately positionned.
Reasons for inaccurate reading of double inflation
Wrongly sized cuff
Accurate readings are highly correlated with the size of the cuff. A cuff that is too small will provides incorrectly high results, up to 40 mmHg. The same goes in the opposite direction. A cuff that is too large will show low readings. It may also overload the pump resulting in an error message.
Choosing the right size is easy. The American Medical Association provides guidelines for choosing an ideally sized cuff depending on the arm circumference.
Another way to avoid any incorrect reading and to choose the ideal bladder size is to stick to the two following principles:
- The bladder length should represent 80% of the distance between the shoulder and the elbow,
- The bladder width should be 40% of the arm circumference.
Cuff not properly located
Not properly positioning the cuff is also a common source of error that leads to inaccurate reading and over-inflation. When inflating, the cuff should block the brachial artery. Place the arm cuff approximately half an inch above the elbow of the left arm.
For wrist blood pressure monitors, the hand should be standing palm up with the display clearly visible.
To avoid any issue with the pump, always use the cuff directly on your bare skin and not over a shirt or sweater.
Limb not adequality positionned
Errors in the readings and the pumping process could also appear if the arm is not properly positioned relative to the heart. The Blood Pressure Monitor should be at the heart level, and you should ideally be still and seated. This is especially important with wrist blood pressure monitors. You will need to raise your arm to reach the heart level slightly.
Other reasons leading to the cuff inflating twice or too much
Some devices come with built-in memory, and if several people use the same device, the pressure applied may be too high, leading to a painful experience.
Automatic Blood Pressure Monitors rely on the detection of oscillation through the arm. If the cuff is not properly positioned, the sensors may not detect the blood flow. They may release some air and start the inflation process one more time.
Finally, no technology is 100 percent reliable. If an error message does not appear, the easiest way to check for proper operation is to take three measures in the same settings and conditions. If the readings are different, return the device to the maker.