The diagram shows a researcher using a spirometer to record changes in the volume of air breathed by a person at rest and then after gentle exercise. The pe...
Question 1 Report
The diagram shows a researcher using a spirometer to record changes in the volume of air breathed by a person at rest and then after gentle exercise. The person wears a nose clip and breathes through a tube. Carbon dioxide is absorbed in a chamber containing soda lime, so the trace falls slowly over time.
(a) Name the gas absorbed by the soda lime. [1]
(b) Describe the pattern of breathing shown by a spirometer trace for a resting person. [2]
(c) Explain why the trace has larger waves after exercise. [3]
(d) Explain why the overall trace falls when carbon dioxide is absorbed but oxygen is not replaced. [3]
(e) Design a safe comparison of breathing rate before and after two different activities using this apparatus. [4]
(f) Suggest two reasons why the researcher should not test a person with a known serious lung condition without medical advice. [2]
Answer Details
(a) Soda lime absorbs carbon dioxide. [1]
(b) A resting spirometer trace has regular up-and-down waves. [1] Each wave represents breathing in and out, or one tidal volume. [1]
(c) Exercise increases respiration in muscle cells. [1] More oxygen is needed and more carbon dioxide is produced. [1] Breathing becomes deeper, so tidal volume increases and the trace has larger waves. [1]
(d) Carbon dioxide in exhaled air is removed by soda lime. [1] Oxygen is taken from the spirometer air into the blood. [1] Since carbon dioxide is not returned to replace this oxygen, total gas volume decreases and the trace falls. [1]
(e) A safe comparison should obtain informed consent and check health status [1], measure resting breathing rate for a fixed time [1], perform each activity for a fixed duration and intensity [1], then immediately measure breathing rate for the same time [1]. Allow recovery before the second activity, keep the same person, apparatus and room conditions, and repeat trials to calculate mean rates. Any four points gain the marks.
(f) Exercise or breathing through the apparatus could trigger breathing difficulty in someone with serious lung disease. [1] The test may be unsafe or require interpretation by a health professional. [1]
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