How to Listen to a Mercury Sphygmomanometer163

A mercury sphygmomanometer is a medical device that is used to measure blood pressure. It consists of an inflatable cuff, a mercury manometer, and a stethoscope. The cuff is wrapped around the upper arm and inflated until the blood flow in the brachial artery is occluded. The pressure in the cuff is then slowly released while listening to the sounds of blood flowing through the artery with a stethoscope. These sounds, known as Korotkoff sounds, can be used to determine the patient's systolic and diastolic blood pressure.

Listening to Korotkoff Sounds

Korotkoff sounds are divided into five phases. Each phase corresponds to a different stage of blood flow through the artery. The five phases are as follows:
Phase 1: The first Korotkoff sound is a clear, tapping sound that is heard when the cuff pressure is just above the systolic pressure. This sound is caused by the turbulent flow of blood through the partially occluded artery.
Phase 2: The second Korotkoff sound is a softer, more muffled sound that is heard when the cuff pressure is just below the systolic pressure. This sound is caused by the laminar flow of blood through the fully occluded artery.
Phase 3: The third Korotkoff sound is a louder, more distinct sound that is heard when the cuff pressure is just above the diastolic pressure. This sound is caused by the turbulent flow of blood through the partially reopened artery.
Phase 4: The fourth Korotkoff sound is a softer, more muffled sound that is heard when the cuff pressure is just below the diastolic pressure. This sound is caused by the laminar flow of blood through the fully reopened artery.
Phase 5: The fifth Korotkoff sound is a very faint sound that is heard when the cuff pressure is equal to the diastolic pressure. This sound is caused by the complete cessation of blood flow through the artery.

The systolic blood pressure is the pressure at which the first Korotkoff sound is heard. The diastolic blood pressure is the pressure at which the fifth Korotkoff sound is heard.

Interpreting Korotkoff Sounds

The following table shows the relationship between the Korotkoff sounds and the blood pressure:


Korotkoff Sound
Blood Pressure




Phase 1
Systolic pressure


Phase 2
Systolic pressure


Phase 3
Diastolic pressure


Phase 4
Diastolic pressure


Phase 5
Diastolic pressure

It is important to note that the Korotkoff sounds may be difficult to hear in some patients. This can make it difficult to accurately determine the blood pressure. If you are having difficulty hearing the Korotkoff sounds, you may need to use a different type of blood pressure monitor.

Tips for Listening to Korotkoff Sounds

Here are a few tips for listening to Korotkoff sounds:
Use a high-quality stethoscope.
Position the patient in a comfortable position.
Wrap the cuff snugly around the patient's upper arm.
Inflate the cuff until the first Korotkoff sound is heard.
Slowly release the pressure in the cuff while listening for the Korotkoff sounds.
Record the systolic and diastolic blood pressure.

By following these tips, you can accurately measure blood pressure using a mercury sphygmomanometer.

2024-11-07

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