Which instrument is commonly used to measure blood pressure?

• A. Sphygmomanometer
• B. Stethoscope
• C. Thermometer
• D. Pulse oximeter

Answer: (A)

The sphygmomanometer is the primary instrument used to measure blood pressure. This device consists of an inflatable cuff that is wrapped around the upper arm and a pressure gauge that indicates the pressure in the arteries. As the cuff inflates, it temporarily restricts blood flow, and as it deflates, the healthcare professional listens for specific sounds (Korotkoff sounds) through a stethoscope placed over the brachial artery to determine systolic and diastolic blood pressure readings.

A stethoscope, while often used in conjunction with a sphygmomanometer to listen for those sounds, does not measure blood pressure directly. It serves a supportive role by allowing the clinician to hear the sounds that indicate the points at which blood begins to flow again and when it resumes normal flow.

A thermometer’s purpose is to measure body temperature, an entirely different physiological parameter. Similarly, a pulse oximeter measures the oxygen saturation level in the blood, not blood pressure, by using light absorption of hemoglobin at specific wavelengths.

Thus, the sphygmomanometer is the only instrument specifically designed for and capable of accurately measuring blood pressure, making it the correct answer.