Both aneroid and mercury sphygmomanometers are used by nurses, doctors, EMTs, and regular people everywhere – so which is better? That’s a break room or casual conversation argument that would probably only come up between nurses or healthcare professionals.

That question doesn’t have a simple answer. It hinges on one important nuance in the question – that being what you mean by the word “better”. Does better mean more accurate? Or does it mean easier to use? Or more portable? How about which is the best blood pressure kit for nurses to use?

There’s a lot of different ways you can define better when comparing aneroid and mercury sphygmomanometers. But wait – which is more accurate, digital, or manual blood pressure cuffs? The digital models are high-tech and don’t require a stethoscope – that’s better. Well, that’s a question that we’re not tackling here, but you can follow the link to find the answer.

So let’s see if we can settle this question once and for all and get to the heart of the question: “Are aneroid or mercury sphygmomanometers better?” To do that, first, we’ll need to understand exactly how a sphygmomanometer works and what makes the two blood pressure measuring devices different.

 

How A Sphygmomanometer Works

 

All sphygmomanometers do the same thing – restrict circulation in the arm and use a measuring device to indirectly measure the pressure of the blood pulsating in the veins and arteries. A modern sphygmomanometer, regardless of whether it is an aneroid or mercury type (digital models are a bit different), uses the same basic equipment to restrict blood flow. The only difference is the type of measuring device.

The two types of devices share four main parts, which include:

  • Measuring device – either a mercury column or dial gauge
  • Air bladder – fills with air to restrict blood flow
  • Bulb pump, tube, and release valve – how you fill the air bladder with air to get the systolic reading and then release the air to get the diastolic pressure
  • Cuff – the cuff retains the air bladder and fixes it securely around the upper arm

You’ll notice the only difference was the equipment used to measure the blood pressure – a mercury column or dial gauge. Let’s talk about the difference between the two.

 

How A Mercury Column Works

From the Greek word “sphygmos“, pulse; and French word  “manomètre“, pressure meter. The modern sphygmomanometer was first invented in 1881 by Samuel Siegfried Karl Ritter von Basch an Austrian physician. 

An interesting side-note here is that he was the personal physician to the first and only emperor of Mexico, Maximilian I. His model used water instead of air to inflate the bladder and restrict blood flow, but it measured blood pressure with a mercury column very similar to the ones still in use today. It’s a very simple measuring device – it’s nothing more than a column of mercury with measurements on it like a thermometer. The mercury rises and falls with the amount of pressure measured by the cuff.

This elegantly simple design is the main reason it is so accurate and considered the gold standard in blood pressure measuring devices. Because it’s so simple – just a column of mercury – it has fewer moving parts and therefore, less that can go out of whack and put it out of calibration.  That’s why it’s so accurate.

 

How An Aneroid Dial Gauge Works

Aneroid sphygmomanometers use a spring device and metal membrane to transmit the pressure from the air bladder. These are located in the round dial gauge. An indicator needle registers the pressure reading, given by the numbers around the dial.

With more moving parts than a mercury sphygmomanometer, aneroid models must be calibrated more often to ensure accurate readings.

 

So Which Is Better?

 

Did you make it through all the geek-talk reviews about the differences in mercury and aneroid sphygmomanometers, or did you skip straight to dessert? It’s OK if you did and if you’re here, let’s get the question answered:

Which is better – aneroid or mercury sphygmomanometers? The answer: it depends.

Sorry, that may not be a satisfactory answer, but it comes back to the definition of better – so let’s break “better” down for each type of sphygmomanometer.

 

Better For Accuracy – Mercury Sphygmomanometer

If you need a high level of accuracy, the mercury sphygmomanometer is hands down the top. It’s the gold standard, and even though it is being phased out in some clinical settings because of the environmental risks posed by the mercury inside of it, it still sets the standard.

 

Better For Portability – Aneroid Sphygmomanometer

Coming in a very close second is the aneroid sphygmomanometer. Because it uses a dial gauge instead of a mercury column, it’s more portable and easier to use while still giving an accuracy within the 4 mmHg range required for clinical use. That’s why you see them used more widely than mercury sphygmomanometers. And if you want to know are aneroid sphygmomanometers accurate, you can look here.

 

Easiest To Use – Digital Sphygmomanometer

Sure, we didn’t cover digital sphygmomanometers, but if you want to consider ease of use, they take the prize because everything is controlled by the internal computer and you don’t need a stethoscope to take a reading. However, you do give up a degree of accuracy.

 

So the next time someone asks you: “Which is better: an aneroid or mercury sphygmomanometer?” – you can ask this question in response:

“What do you mean by better?”

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