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Knowing how to use a sphygmomanometer to properly check blood pressure is important.

The pandemic and the forced lockdown meant that sales of sphygmomanometers for home use soured during 2020. I have reviewed some of the best for clinical and home use here.

The bottom line is, more people are using sphygmomanometers to test their own blood pressure and more questions are arising on exactly how to use them.

So that’s what we look into today. I’ll take it step by step, however.

First, we’ll look at what a Sphygmomanometer is, how it works, and how to use it. Most important of all, we’ll cover what the readings actually mean.

So if you’re ready, let’s jump in.

What is a Sphygmomanometer?

A sphygmomanometer is a small instrument that measures blood pressure.

There are various components to the Sphygmomanometer. One part is an inflatable rubber cuff, which wraps around the patient’s arm.

Connected to the cuff is a measuring device that will show the cuff’s pressure as the reading is taken.

A third component is a small (normally rubber) bulb that is used to inflate the cuff.

Finally, a release valve is used to allow air to escape the cuff.

A stethoscope is also used to listen to arterial blood flow sounds as the cuff is applied to the patient.

How a Sphygmomanometer works to take readings

As your heart beats, blood is forced through your arteries. This rise in pressure as the blood is pumped out of the heart is called systolic pressure.

As the heart contracts and the ventricles prepare for another beat, there is a reduction in pressure. This low-pressure period is called diastolic pressure.

Essentially, it is the difference between these two pressures that the Sphygmomanometer is reading.

The process begins with the cuff. When this is attached to the patient’s arm and the air is pumped into it, the cuff becomes inflated to above the expected systolic pressure.

The user then opens the valve so that cuff pressure slowly decreases to a level where it is equal to the arterial systolic pressure.

At this point, blood begins to flow past the cuff creating sounds (known as Korotkoff sounds) that can be detected with a stethoscope.

The sounds are heard and the cuff’s pressure is recorded, while air is slowly released using the valve.

When the cuff’s pressure falls below the arterial diastolic pressure the blood flow sounds will stop. This point indicates the diastolic pressure and is recorded accordingly.

Systolic and diastolic pressures are recorded as systolic ‘over’ diastolic, (e.g 120 over 80).

How to use a Sphygmomanometer

Now that we understand how a Sphygmomanometer works, it should be clearer the steps involved to use one.

Let’s go through those now.

Step 1

Wrap the cuff around the upper arm of the patient. The cuff’s lower edge should be one inch above the antecubital Fossa, (see video above for an example of good cuff placement).

Step 2

Inflate the cuff using the bulb so that the pressure reads to around 180mmHg.

Step 3

Start to release air from the cuff using the escape vale, (no faster than 3mm/sec).

Step 4

With the stethoscope in place, listen to the subject’s blood flow on the forearm just below the cuff. While doing this, observe the dial or mercury gauge of the Sphygmomanometer.

Step 5

Start taking the readings of the dial or gauge. The first knocking sound (Korotkoff) you hear as you decrease the pressure will be the subject’s systolic pressure.

The point at which the sound disappears will be the diastolic pressure.

Step 6

Repeat the process again on the other arm, (while also making a note of the difference between the two readings).

It is good practice to make a note of the patient’s position, whether you are reading the right or left arm, and what the cuff size is.

How to use a Sphygmomanometer – Understanding the Readings

So, you have used the Sphygmomanometer to take readings on yourself, or whomever you are taking care of, and it is now time to decipher what you’ve recorded.

Generally speaking, a normal test will read something like 120/80 (systolic/ diastolic).

If you have recorded a reading between 120 and 139 for systolic and 80 to 89 for diastolic, it could mean that the patient has possible prehypertension.

(The fact a Sphygmomanometer is used at home, would also indicate this, as they are a way for hypertension sufferers to record and keep track of their levels)

If your systolic is between 140 and 150, and your diastolic is between 90 and 99, in medical terms you likely have stage I hypertension.

A systolic exceeding 160, with a diastolic over 100, indicates Stage II hypertension.

Stage III hypertension is over 180 systolic, and 110 diastolic or higher.

If you take readings and they are more severe than you expected; do not panic. False readings can occur and you should always take more than one.

Wait a few hours, reapply the cuff and try again. In the interim, ensure that you do not consume any stimulants such as coffee, or do extreme physical exercise.

If after taking further readings the situation remains the same, you should arrange a trip to your doctor for reading there, and further advice about your blood pressure and what to do.

About Hannah Drake

Hannah Drake, RN, CSP is a registered nurse and owner and founder of Nurse Focus. Her nursing career spans almost two decades, and in that time she has developed her skill base across a variety of settings, including med surg nursing, clinical informatics system administration and implementation, and healthcare community management. Contact Hannah.

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