Explain how a spirometer is used to measure lung function and describe what the measurements can tell a doctor about a patient's respiratory health.

AQA A-Level Physics (7408) — 3.10.3 Biological Measurement · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

A spirometer measures the volume of air breathed in and out. The patient breathes into a mouthpiece or tube and the changes in volume are recorded over time. From the trace the tidal volume – the volume of air in a normal breath – can be measured. The breathing rate can also be determined from the trace. Abnormal tidal volume or breathing rate indicates a respiratory condition or reduced lung function.

Examiner tips

  • Use the term ‘spirometer’ and explain it measures air volume.
  • Mention the mouthpiece/tube and recording of volume over time.
  • State tidal volume and breathing rate as key measurements.
  • Link abnormal values to possible respiratory conditions.

Common mistakes

  • Confusing tidal volume with total lung capacity.
  • Forgetting to mention the mouthpiece or tube.
  • Not relating abnormal values to respiratory health.

Mark scheme (5 marks)

  1. A spirometer measures the volume of air breathed in and/or out
  2. The patient breathes into the spirometer (mouthpiece/tube) and the changes in volume are recorded over time
  3. Tidal volume can be measured — the volume of air in a normal breath
  4. Breathing rate can be determined from the spirometer trace
  5. Abnormal tidal volume or breathing rate can indicate a respiratory condition / reduced lung function

Key terms in this question

spirometer · lung function

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