The stethoscope is used to listen to the blood pressure sounds, which are calle
The stethoscope is used to listen to the blood pressure sounds, which are called Korotkoff sounds.
Stethoscope Usage and Korotkoff Sounds
The stethoscope is used on bare skin so that a client’s clothing does not affect the sounds. The stethoscope does not make sounds louder; it simply blocks out extraneous noises so you can better hear the Korotkoff sounds. These sounds are heard through a stethoscope applied over the brachial artery when the blood pressure cuff is deflating. You will not hear anything when you first place the stethoscope over the brachial artery because unobstructed blood flow is silent. The Korotkoff sounds appear after you inflate the cuff (which compresses the artery/blood flow) and then begin to deflate the cuff. The Korotkoff sounds are the result of the turbulent blood caused by the inflated cuff compressing the artery and oscillations of the arterial wall when the heart beats during cuff deflation.
Here are a few tips:
- Use a high quality stethoscope with durable, thick tubing. Avoid stethoscopes with long tubing because this can distort sounds.
- Ensure quiet surroundings so that you can better hear the Korotkoff sounds.
- Make sure that the slope of the stethoscope earpieces point forward or toward your nose.
- Use a stethoscope that has both bell and diaphragm capacity. See Figure 5.4 for bell and diaphragm.
Figure 5.4: Stethoscope with bell and diaphragm (Illustration credit: Hilary Tang)
- Cleanse the stethoscope prior to use including the ear pieces and the bell and diaphragm.
- The bell of the stethoscope is suggested because it is used for low-pitched sounds like blood pressure. However, some healthcare providers use the diaphragm for several reasons: that is how they learned to take blood pressure; they believe this helps them hear the Korotkoff sounds better; and the diaphragm covers a larger surface area than the bell.
- Hold the bell lightly against the skin with a complete seal or hold the diaphragm firmly against the skin with a complete seal.
- You must ensure that the bell or diaphragm is open before using. See Film Clip 5.2 on how to open and close the bell and diaphragm.
Film clip 5.2: Opening and closing the bell and diaphragm
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Determining Maximum Inflation Pressure
Healthcare providers determine the maximum inflation pressure before they take blood pressure. The maximum inflation pressure is the number on the sphygmomanometer that the cuff is inflated to when measuring blood pressure. If you do not determine the maximum pressure inflation, an auscultatory gap could go unrecognized, and as a result the blood pressure could be underestimated (lower than the actual value).
An auscultatory gap is a silent interval when the Korotkoff sounds go absent and then reappear while you are deflating the cuff during blood pressure measurement. This gap is an abnormal finding and can occur due to arterial stif