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Measuring blood pressure

Specification reference:

  • P1.5.1 Pressure in a fluid

Aims

You are likely to have your blood pressure measured by a doctor at some point in your life, and it is one way that doctors check up on your health. Your blood is a fluid contained within your heart and blood vessels, all of which are connected together to make the circulatory system. The blood exerts a certain force per unit area – a pressure – on the heart and blood vessels. In this activity you will carry out research to find out more about blood pressure and how it is measured.

Learning objectives

After completing the activity you should be able to:

  • explain what is meant by ‘blood pressure’
  • know the units blood pressure is measured in, and explain what those units mean
  • explain how one method for measuring blood pressure works.

Task

You are going to design a leaflet or poster for a GP surgery, describing and explaining the science behind the measurement of blood pressure. Below is a list of things you should try to include (although they do not have to be in the same order as they are listed here).

1The unit of blood pressure (mm Hg, also called torr), and what this means

2Why blood pressure measurements consist of two different pressures (‘systolic’ and ‘diastolic’), and what each one means

3How blood pressure can be measured using a stethoscope together with a device called a sphygmomanometer consisting of an inflatable cuff and a mercury manometer

4Optional: How an aneroid manometer, which is often used these days instead of a mercury manometer, works

5The range of blood pressures which is considered to be healthy

6Why a person’s blood pressure rises if their blood vessels become narrowed.

To help you, use the Internet and books for research. Search for combinations of terms such as “measuring”, “blood pressure”, and “sphygmomanometer”, or “how a mercury sphygmomanometer works”. Do not include anything in your leaflet or poster which you do not understand.

You might like to get started by watching the 4-minute clip at from the BBC series ‘Bang Goes the Theory’, which is about the history of blood pressure measurement and how a sphygmomanometer works (in this case, using a column of water instead of mercury).

© Oxford University Press 2016

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