why can't you normally hear the sounds of Korotkoff in the brachial artery before you inflate the cuff?

Answer 1

There's probably not enough pressure on the artery.

Answer 2

The sounds heard during measurement of blood pressure are not the same as the heart sounds 'lub' and 'dub' that are due to the closing of the hearts valves. If a stethoscope is placed over the brachial artery in the antecubital fossa in a normal person (without arterial disease), no sound should be audible. As the heart beats, these pulses are transmitted smoothly via laminar (non-turbulent) blood flow throughout the arteries and no sound is produced. Also, if the cuff of a sphygmomanometer is placed around a patient's upper arm and inflated to a pressure above the patient's systolic blood pressure, there will be no sound audible. This is because the pressure in the cuff is high enough such that it completely occludes the blood flow.

Answer 3

Korotkoff described the sequence of vascular sounds heard with a stethoscope over the brachial artery during deflation of a pneumatic cuff.
The clinical measurement of blood pressure is generally obtained by auscultation for Korotkoff's sounds over the brachial artery using a sphygmomanometer and cuff. Real-time two dimensional ultrasound and Doppler techniques were used to study the brachial artery movements and blood flow patterns during these pressure measurements. Simultaneous recordings of Korotkoff's sounds were obtained. A strong correlation in time was demonstrated between Korotkoff's five phases, brachial artery wall movements and specific blood flow patterns. The evidence largely supports what to date has been speculation as to the origin of Korotkoff's sounds in that Korotkoff's phases 1 and 3 appear to be produced by vigorous arterial wall motion and phase 5 by cessation of this movement. Phase 2 is produced by blood flow disturbance.
Please see the web pages for more details on Korotkoff sounds.

Answer 4

The sounds are a result of turbulence in the flow of blood through the artery.Thus, when the cuff is not inflated, there is not much external pressure and the flow of blood is smooth. When pressure via the cuff if exerted however, the diameter of the artery becomes smaller and the flow changes from laminar(smooth) to turbulent flow. Just like water running thru a hose - it can be quiet at first but when you squeeze the middle you might hear a gurgling noise.

Answer 5

When you can hear the sounds in an artery (with a stethoscope) without applying pressure to the artery to disrupt blood flow, that is called a bruit (pronounced 'brew -eee'). A bruit is a sign of a very serious and very dangerous condition in the artery.

Answer 6

3 years ago, I was diagnosed - hypertension with a reading of 160/100. I used to feel dizzy a lot, my legs had awful cramps, and levels were very low in my potassium, causing my fingers and toes to always cramp together. One day I started to feel really faint while I was driving with my daughter in the back seat and I passed out, hitting 3 cars and ending up in a ditch. That moment,I knew I had to do something because my meds weren't working. I heard about this diet from a friend and thought I'd give it a shot. The results have been remarkable. In just 21 days, I honestly can't remember feeling this good, my blood pressure went from 175/110 to 125/70.

Answer 7

You need a stethescope to hear it...and the manometre and cuff to help measure it. The cuff is inflated, ceasing the blood flow or at least slowing it down dramatically. Upon release of the cuff valve, the fist sound heard (auscultated) is the systolic pressure point..the last sound is the diastolic pressure point to be recorded.
I believe we cannot hear it withour the inflation of the cuff because we need to first stop the blood flow, then have the first sound we hear to record the pressure..which is caused by the rush of blood throught the vein, causing the sound of rebound.

Answer 8

Korotkoff Sounds Phases