There’s a reason nurses, doctors, EMTs, and healthcare professionals across the board still use manual blood pressure cuffs (sphygmomanometers) when there are digital cuffs available. Shouldn’t the newer, more technologically-advanced model be more accurate?
It’s a good question that’s kicked off many scientific papers, articles, and studies on the accuracy of digital sphygmomanometers versus manual versions. There are arguments, statistics, and numbers both for and against the effectiveness and accuracy of digital blood pressure cuffs. There are those who say digital sphygmomanometers aren’t accurate enough for clinical settings and those who say that the old manual versions are destined for the dustbin of history.
We’re going to look at both types of blood pressure cuffs, review how they work, and look at what researchers are saying about the digital revolution. And then we’ll see about answering that question – which one is more accurate?
How A Manual Blood Pressure Cuff Works
There are two types of manual blood pressure cuffs: aneroid and mercury. They both use the same cuff, bladder, pump bulb, and release valve, but use different devices to measure blood pressure.
An aneroid sphygmomanometer (blood pressure cuff) uses a spring device and metal membrane to transmit the minute pressure changes against the air bladder as the heartbeats. The pressure is indicated by an arrow indicator on a round dial gauge. Most aneroid models can reliably measure blood pressure within the clinical standard of a 4 mmHg range.
If you’re wondering what kind of features the best aneroid sphygmomanometers offer, check out this article.
A mercury sphygmomanometer uses a column of mercury (similar to a thermometer) to measure blood pressure. It is considered the gold standard of blood pressure measuring devices. However, regular calibration is necessary to ensure accurate readings – Here’s how to calibrate a blood pressure cuff.
How A Digital Cuff Measures Blood Pressure
Digital blood pressure cuffs use sensors to detect and measure the vibrations of arterial walls as the blood flows through them between systolic and diastolic pressure or oscillatory blood pressure.
A small computer uses an algorithm to compute the systolic and diastolic pressure. Each brand of digital cuff has its own proprietary algorithm to make the calculation.
Dangers Of Inaccurate Blood Pressure Readings
Inaccurate blood pressure readings can be caused by a number of factors. These include:
- Operator error
- Improper patient positioning
- Patient anxiety
- Patient body position
- Body movement
These affect the readings of both digital and manual blood pressure cuff readings. It can result in an exaggerated blood pressure reading and incorrect diagnosis of hypertension. That leads to drugs prescribed and treatments that may not be necessary.
That’s why the accuracy of the device used to measure blood pressure is so critical and why the question of whether or not a digital cuff is accurate enough for clinical use continues to be argued.
Which Is Better: Digital Or Manual Blood Pressure Cuffs?
So the question then becomes, which is better: aneroid or mercury sphygmomanometers? There’s evidence both for and against the accuracy of digital blood pressure cuffs. But the different proprietary algorithms used between the brands, without a universal standard, opens up many opportunities for inconsistencies in readings.
Digital cuffs do cut out the need for a stethoscope and reduce user error, but manual blood pressure cuffs have decades of verified performance within a 4 mmHg range which is recommended by the Association for the Advancement of Medical Instrumentation.
Until digital blood pressure cuff technology can reliably and repeatedly measure within the 4 mmHg range, the manual blood pressure cuff will probably remain the primary go-to tool for measuring blood pressure in hospitals and clinical settings.
What Researchers Are Saying
There are a large number of papers on both sides of the argument showing research, statistical analyses, and measurements supporting their views. We’ll give you a couple of the most convincing findings from both sides:
Digital Blood Pressure Cuffs Are More Accurate Than Manual Ones
A 2019 paper published in the JAMA Internal Medicine journal reviewed 31 articles with more than 9,000 participants and found that the measurements of blood pressure by digital blood pressure cuffs matched ambulatory blood pressure and didn’t exhibit the “white coat effect” of anxiety that some patients feel during a BP reading.
The paper asserted that automated office blood pressure readings were more accurate and should replace the current use of manual models used by healthcare professionals.
One point: in this study, the patient was alone in a room with an automated device.
Digital Blood Pressure Cuffs Are Inaccurate
A 2017 study compared manual versus automated blood pressure management in intensive care units, coronary care, and ER settings. It recorded that blood pressure was frequently recorded higher, often differing by as much as 15 mmHg higher.
Their conclusion was that they could not completely trust digital blood pressure cuffs in a hospital or critical care settings.
Although digital blood pressure cuffs are easier to use and can still produce accurate readings, because an aneroid model, when properly calibrated and operated, is more reliably accurate with a small margin of error, it wins out.
For home use, quick readings, and situations where clinical accuracy isn’t required, digital blood pressure cuffs are fine. But in clinical settings, hospitals, clinics, and emergency services, the aneroid blood pressure cuff sets the standard for accuracy and reliability.