CCEA A-Level Life and Health Sciences 0008
Experimental Techniques
Human Body Systems
Physical Chemistry in Industrial Processes
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Organic Chemistry
Medical PhysicsA2 option
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Medical Physics
Blood pressure readings and the sphygmomanometer
- 3 things to know
- A2 3
Overview
mmHg and kPa conversion, Korotkoff sounds, mercury, aneroid and digital sphygmomanometers, cuff size and reliable readings, white coat hypertension, low readings and pulse pressure.
What you need to know
Answer each one before you reveal it.
Convert a systolic pressure of 120 mmHg into kilopascals, given that 1 mmHg is 133.3 Pa.
What are Korotkoff sounds?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What unit is blood pressure measured in, and where does the unit come from?
Model answer
Blood pressure is measured in millimetres of mercury, mmHg. The unit is the height of a mercury column that the pressure would support.
- 2
Convert a systolic pressure of 120 mmHg into kilopascals, given that 1 mmHg is 133.3 Pa.
Model answer
A pressure of 120 mmHg is about 16.0 kPa. The working is 120 × 133.3 Pa = 15 996 Pa, which is 16.0 kPa.
- 3
What are Korotkoff sounds?
Model answer
Korotkoff sounds are the tapping sounds heard through a stethoscope as blood spurts through a partly squeezed artery. The sounds are heard over the brachial artery just below the cuff.
- 4
How are Korotkoff sounds used to read systolic and diastolic pressure?
Model answer
The cuff pressure at which the first tapping sound is heard is the systolic pressure. The pressure at which the sounds disappear is the diastolic pressure.
- 5
Why must the cuff first be inflated above systolic pressure?
Model answer
A cuff pressure above systolic pressure squeezes the brachial artery shut. Blood cannot flow, so no sound is heard until the pressure is let down.
- 6
How does a mercury sphygmomanometer display the pressure?
Model answer
The cuff is connected to a column of mercury in a glass tube with a millimetre scale. The cuff pressure pushes the mercury up to a height equal to the pressure in mmHg.
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