Your Questions About Korotkoff Sounds and Blood Pressure
November 11th, 2015 by health

John asks…

How are the Korotkoff sounds produced?

How are the Korotkoff sounds produced? When do you hear the first Korotkoff sound? When do you hear the last Korotkoff sound?

Health answers:

Korotkoff sounds in the arteries are caused by turbulence of the blood.

hearing-Korotkoff-Sounds

When using a BP cuff, several conditions occur:

When cuff pressure is above systole pressure – No blood can get through the artery.

When the cuff pressure is equal to the systole pressure – Blood is able to burst through the artery – I use the term “burst” as it is not a constant flow, as the diastolic pressure is still below the cuff pressure. At this point, you will hear your first Korotkoff sound.

As the cuff pressure lowers Korotkoff sounds continue – although they get softer. These sounds are caused, as previously stated, by turbulence of the blood, which is caused by the squeezing of the artery by the cuff. This squeezing leads to two areas of the artery having different diameters. The turbulence occurs when the blood from the squeezed artery is released into a wider diameter artery. This location is usually around the elbow – Which is why the stethoscope is placed there.

The last sound occurs when diastolic pressure equals cuff pressure. Once the diastolic pressure is above cuff pressure, then no squeezing of the artery occurs, thus no Korotkoff sounds.

In summary:

First sound – is when cuff pressure = Systole pressure
Last sound – is when cuff pressure = Diastolic pressure

Note: This is the most common way of measuring BP


Sandra asks…

Can you take a blood pressure by watching the meter jump instead of listening to korotkoff sounds?

Will the needle on the meter jump when the systolic pressure goes through and also with the diastolic?

Health answers:

No, you cannot. You must listen for the Korotkoff sounds to get an accurate systolic and diastolic blood pressure reading. The bumping of the needle often seen on the sphygmomanometer may or may not correlate with the blood pressure and should not be used to determine the blood pressure reading.


Thomas asks…

How are the sounds of Korotkoff made in reference to the systolic and diastolic pressures?

health answers:

The basic Korotkoff sound is caused by pressure exerted on the brachial artery. The first is heard when the pressure in the cuff drops below the systolic pressure, and blood “spurts” through the artery. The sound disappears when the cuff pressure drops below diastolic pressure and there is no longer any restriction of blood flow.

Depending on the actual cuff pressure, the sounds vary in quality and amplitude.


Donna asks…

Question on Korotkoff sounds?

It takes more pressure to collapse stiff arteries than young healthy ones and hear the Korotkoff sounds appear then disappear. So whatever the pressure of the blood in the artery is, it will appear to be higher in those with sclerosis than those without.
How do doctors differentiate between the pressure of the blood going through normal arteries and those which have stiffening?

Perhaps I should re-word that as ” What provision is made in automatic digital monitors to differentiate between the pressure of the blood and the apparent extra, caused by stiffening?”

Health answers:

To answer your specific question, no provision is made, either by doctors (who can be forgiven) or the manufacturers of digital monitors (who should know better), to differentiate between the true readings, of the internal blood pressure, and the additional pressure required to collapse hardened arterial walls to induce the appearance and disappearance of Korotkoff’s sounds, which are of course, those of turbulence when laminar flow breaks down.

The structural integrity of the conduits is much greater when arteriosclerosis is present, and can add as much as 80% of the actual internal, true pressure, which more than accounts for the apparent rise in systolic and diastolic pressures ascribed to so-called “age-related hypertension”. This is an almost entirely spurious concept, but it seems to have never occurred to the medical profession to question it, and ask why the numbers don’t add up. Admittedly, greater pressure is actually needed, to eject a volume of blood across the aortic valve into the root of a less elastic aorta, but the flawed measurement technique hugely exaggerates this, rendering the readings virtually meaningless.

It’s not just sphygmomanometry that’s at fault of course. Tonometry suffers from exactly the same defect, in relying on deformation of the arterial wall, – and this is affected by stiffness and structural integrity – despite being considered the preferred and more accurate technique, which needless to say, it isn’t.


Jenny asks…

For EMTs: Why is it so difficult to hear Korotkoff sounds when measuring a patient’s blood pressure?

Recently I became an EMT, and I’m embarrassed to admit that I have an incredibly difficult time obtaining a blood pressure using traditional methods. I’m sure that my cuff placement is correct, but when I attempt to palpate for a brachial pulse or to auscultate Korotkoff sounds I’m usually at a loss.

I don’t really have anyone to practice on, so I’ve practiced on myself at home, and I can locate and hear my pulse for a consistently accurate BP measurement about sixty percent of the time, but when measuring vitals on a patient I can’t replicate my actions for some reason.

Any suggestions? What am I doing wrong? I know I’m not just deaf… why is it so difficult to hear what I need to hear, even when the truck is stopped and quiet? I’d hate to make a mistake in the field because of this.

Health answers:

Hmmmm…..
I am not exactly sure what to tell you. When trying to auscultate a BP the head/drum of the stethoscope is partially under the cuff above the bend in the elbow. I would recommend practicing on anyone that will sit still for 30 seconds.

If you can find a radial pulse you can palpate the BP as well. This method is not always as accurate, but it should give you an indication or a way to high or way to low BP.

If you currently have a job in EMS ask a medic that you feel comfortable with to help you out. I suggest that medics make their new EMT’s practice on them… even to the point of starting IV’s… You also need to make sure you are relaxed and that the bell of the steth is turned the correct direction, if you are using a double sided one and you have the ear pieces facing the correct direction in your ears. (simple things that can make a big difference)

If you are not hearing it then something is going wrong… cause I can promise you that most of your patients will have a BP 🙂 Just keep trying to practice on others.

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Answers provided are not medical advice – you should always consult your doctor.


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