The Sphygmomanometer 1881 – Measuring Systolic and Diastolic Blood Pressure

Blood pressure measurement is a good example of doctors' dependence on technology in caring for patients. Today, arterial blood pressure is usually measured with a blood pressure monitor. Traditionally, this device uses a column of mercury to measure pressure. 

• Systolic pressure (the upper reading) reflects the pressure during contraction of the heart's ventricles. For a normal adult, systolic pressure is 110-120 millimetres of mercury. 
• Diastolic pressure (the lower reading) is the minimum pressure in the arteries and occurs when the ventricles fill with blood. For a normal adult, diastolic pressure is 80 millimetres of mercury.

The evolution of blood pressure monitors has an interesting history full of ingenious inventions:

• In 1733, British physiologist Stephen Hales connected a long glass tube to an artery in a horse's neck and observed blood rising 2.9 m. Hales thus documented measurements of an animal's blood pressure for the first time. 
• In 1881, Austrian physician Samuel von Basch carried out studies on measuring systolic pressure. 
• In 1896, Italian physician Scipione Riva-Rocci turned to the use of an inflatable cuff around the arm to apply steady pressure over an artery. 
• In 1905, Russian physician Nikolai Korotkov used a stethoscope to listen to sounds from an artery as cuff pressure was reduced, making it possible to measure diastolic pressure.

After 1910, US doctors regularly reported systolic and diastolic blood pressure in clinical reports about their patients.

The lower and upper blood pressure readings can indicate serious health conditions. For example, high blood pressure is a risk factor for stroke, heart attack and kidney failure. Today, blood pressure monitors allow doctors to diagnose low and high blood pressure. Electronic devices that do not require mercury-based monitors have also become widespread.

Description of the article image: A depiction of British physiologist Stephen Hales measuring a horse's blood pressure in 1733. 

Historical figures mentioned in the article: Stephen Hales (1677–1761), Samuel Siegfried Karl Ritter von Basch (1837–1905), Scipione Riva-Rocci (1863–1937), Nikolai Sergeyevich Korotkov (or Korotkoff) (1874–1920)

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