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Which instrument is used to measure blood pressure?
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Answer: Option C — Sphygmomanometer
Detailed Solution
A sphygmomanometer (from the Greek words "sphygmos", meaning "pulse", and "manometer", a pressure meter) is an instrument used to measure blood pressure. It was invented by Samuel Siegfried Karl von Basch in 1881, and the version with an inflatable cuff, used today, was developed by the Italian physician Scipione Riva-Rocci in 1896. In 1905, the Russian surgeon Nikolai Korotkov described the method of listening to sounds in the artery with a stethoscope, which is still used.
A traditional sphygmomanometer has three main parts:
- An inflatable cuff, wrapped around the upper arm.
- A bulb, used to pump air into the cuff.
A manometer, a gauge that shows the pressure, either a column of mercury or a dial (aneroid). Digital monitors use electronic sensors.
How it works: The cuff is inflated until it stops the blood flow in the brachial artery. Then the air is slowly released while a doctor listens through a stethoscope. The pressure at which the first sound of blood flow is heard is the systolic pressure, and the pressure at which the sounds disappear is the diastolic pressure.
Blood pressure is the force exerted by circulating blood on the walls of the arteries. It is measured in millimetres of mercury (mmHg) and written as systolic over diastolic:
Systolic pressure: the pressure when the heart contracts (ventricles pump blood).
Diastolic pressure: the pressure when the heart relaxes between beats.
Normal blood pressure for an adult is about 120/80 mmHg. Persistently high blood pressure (hypertension, about 140/90 or above, or 130/80 in newer guidelines) increases the risk of heart attack, stroke and kidney disease. It is called the "silent killer" because it often has no symptoms. World Hypertension Day is observed on 17 May.
Other medical instruments:
- Stethoscope: to listen to heart and lung sounds (invented by René Laennec, 1816).
- Electrocardiograph (ECG): records the electrical activity of the heart.
- Glucometer: measures blood sugar.
- Clinical thermometer: measures body temperature.
Why not the other options?
- ✗A stethoscope is used to listen to internal body sounds.
- ✗A barometer measures atmospheric pressure.
- ✗A manometer measures the pressure of gases and liquids generally.
Quick tip
Remember: Blood pressure = sphygmomanometer (normal 120/80 mmHg); stethoscope = Laennec (1816); barometer = atmospheric pressure; hygrometer = humidity; ECG = heart's electrical activity.
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Units & Measurement — Preparation
This question tests your understanding of Units & Measurement, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers physical quantities and their units: the SI system and its seven base units, derived units, units named after scientists, conversion between units, measuring instruments, and the difference between scalar and vector quantities. Questions commonly ask for the SI unit of a quantity (the newton for force, the pascal for pressure and the joule for energy), what an instrument measures (a barometer measures atmospheric pressure, and a hygrometer measures humidity), and whether a quantity is a scalar or a vector. One light-year is a unit of distance, not time. Practise the units and measurement questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.