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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Electrocardiograph. How Stuff Works


Electrocardiograph is the Medical diagnostic instrument used to record the electrical activities of the heart. It gives a recorded data in the form of a graph called ElectroCardioGram or ECG. Human heart functions through the electrical impulses produced by the specialized groups of cells called Pace makers (SA node and AV node) located on the right surface of the heart. The electrical signals generated by the pace makers will be available on the surface of skin also. The Electrocardiograph detects these signals and output as a graph. By observing the waveform, it is easy to confirm the variations in the functioning of heart.
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