Stethoscope. How Stuff Works


Stethoscope is a medical diagnostic tool for Auscultation which is the listening of internal sounds of the body. Auscultation is used to examine the heart sounds, breath sounds, bowel sounds etc. Auscultation requires skill,  clinical experience and a good quality stethoscope. An experienced physician can distinguish normal Lub and Dub sounds of the heart as well as heart murmurs and gallops. In combination with the sphygmomanometer, the Stethoscope is used to measure the blood pressure. The Stethoscope was invented by Rene Laennec of France in 1816. The two-sided stethoscope was invented by Rappaport and Sprague in the early 20th century.

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Sphygmomanometer. How Stuff Works


The Sphygmomanometer is the diagnostic device used to measure the blood pressure. Blood pressure is the pressure exerted by the blood on the wall of the artery during its flow. It is meant for keeping constant blood flow throughout the body irrespective of the position. Normal blood pressure is 80 mmHg-120 mmHg in which 80 mmHg is the diastolic pressure when the heart relaxed and 120 mmHg is the systolic pressure when the heart contracts. The diastolic pressure up to 90 mmHg and systolic pressure up to 130 mmHg is treated as normal but the person is in the border line of Hypertension. Usually a BP index is used since the BP may vary slightly depending on the conditions of the body and either systolic or diastolic pressure may be high as in the case of aging. Even if we sit in front of the Physician, our BP may increase slightly due to nervousness, a condition called as “White coat effect”. BP index is calculated by adding systolic and diastolic pressures and then dividing by 2. In normal case it is 120+80 / 2 = 100. Up to 110 is treated as normal. BP measurement on both the arms and periodic measurement are advisable to confirm the Hypertension before going on medication.

Conventional Sphygmomanometer is mercury column based and has an inflatable cuff to restrict the blood flow. It is used in conjunction with Stethoscope to hear the sound during the measurement. Sphygmomanometer was invented by Samuel Siegfried Karl Ritter von Basch in 1881.

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