Spirometers (AQA GCSE Physical Education (PE))
Revision Note
Author
Naomi HolyoakExpertise
Biology
Interpretation of a Spirometer Trace
An individual's breathing can be measured an analysed using a piece of equipment called a spirometer
Spirometers function as follows:
The individual breathes via a tube that is connected to a floating box of air
The tube is also connected to a canister of a chemical called soda-lime which absorbs exhaled carbon dioxide; this allows the spirometer to record only the changing volumes of oxygen
An inward breath removes air from the box, causing it to sink lower into the water
Breathing outputs air into the box and causes it to rise up in the water
A metal arm with a pen is attached to the side of the box, and this arm draws a trace on a rotating drum as the individual breathes, producing a spirometer trace
Spirometers can be used by an individual at rest or during exercise, e.g. running on a treadmill
Spirometer diagram
Spirometers can be used to produce a spirometer trace
Spirometer traces can be analysed to determine the following:
Tidal volume
The volume of air breathed in and out with each normal breath
Inspiratory reserve volume
The difference between the tidal volume and the total volume of air breathed in during a deep inhalation
Expiratory reserve volume
The difference between the tidal volume and the total volume of air breathed out during an active exhalation
Residual volume
The volume of air that remains in the lungs even after an active exhalation
Analysis of a spirometer trace allows differences between breathing at rest and breathing during exercise to be determined, e.g.
Changes in tidal volume
Changes in breathing rate
Spirometer trace diagram
A spirometer trace can be analysed to determine tidal volume, inspiratory and expiratory reserve volume, and residual volume
Worked Example
For the spirometer trace provided above, determine the following:
Breathing rate at rest
Maximum tidal volume during exercise
Inspiratory reserve volume
1. Determine the breathing rate at rest
Number of peaks during the first 30 seconds = 6
Multiply to give breaths per 60 seconds = 6 x 2
= 12 breaths per minute
2. Determine the maximum tidal volume during exercise
Maximum volume of air breathed in during exercise = 4.1 dm3
Maximum volume of air breathed out during exercise = 2.3 dm3
4.1 - 2.3 = 1.8 dm3
3. Determine the inspiratory reserve volume
Maximum volume of air breathed in = 4.3 dm3
Air breathed in during a normal breath = 2.95 dm3
4.3 - 2.95 = 1.35 dm3
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