Read breathing depth and rate from a volume trace
Use excursion size for depth and cycle timing for rate in supplied respiratory traces.
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall breathing rate and graph axes.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which trace feature represents depth on a volume axis?
What you will learn
- Separate height from timing
- Compare like scales and distinguish outcomes
Read breathing depth and rate from a volume trace
| Condition | Depth / L per breath | Cycle / s | Rate / breaths per min |
|---|---|---|---|
| Rest | 0.5 | 5 | 12 |
| Activity | 0.75 | 2.5 | 24 |
Separate height from timing
In the supplied schematic lung-volume traces, a breath’s vertical excursion shows the volume change per breath, while spacing between equivalent points shows its duration. Larger peak-to-trough volume change indicates a deeper breath under the same volume scale. Closer successive cycles indicate a higher breathing rate under the same time scale.
The resting teaching trace has a 0.50 L excursion and a five-second cycle. The activity trace has a 0.75 L excursion and a 2.5-second cycle. Depth increases by 0.25 L per breath, and rates are 60/5 = 12 and 60/2.5 = 24 breaths per minute. These traces are schematic supplied data, not recordings from a learner.
Compare like scales and distinguish outcomes
Check the axes before comparing pictures. A taller curve drawn with a different volume scale may represent the same depth; a horizontally compressed drawing may not represent faster breathing if its time scale also changes. Use labelled values and complete cycles rather than the apparent page shape alone.
Physical activity usually increases both rate and depth of breathing, but these are distinct observations. Their product can estimate air moved per minute in the stated simple model; it does not show that all inspired air reaches gas-exchange surfaces or establish clinical performance. Supervised apparatus and practical interpretation still require teacher review.
Sources for this lesson
Pause and explain
What changes in the supplied activity trace?
Worked example
Find the rates for five-second and 2.5-second cycles.
Show the worked solution
- A minute is 60 seconds.
- Divide 60 by each cycle duration.
Answer 12 and 24 breaths per minute respectively.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Read resting and activity depth from the supplied excursions and calculate the change.
Give me a hint
Subtract 0.50 L from 0.75 L.
Compare my reasoning
- Resting excursion: 0.50 L.
- Activity excursion: 0.75 L; difference 0.25 L.
Depth increases from 0.50 to 0.75 L per breath, a 0.25 L increase.
Look for these in your work
- Use excursion values
- Include per-breath meaning
Calculate the two rates from five-second and 2.5-second cycle durations.
Give me a hint
Use 60 divided by cycle duration.
Compare my reasoning
- 60/5 = 12.
- 60/2.5 = 24.
Rest: 12 breaths/min. Activity: 24 breaths/min.
Look for these in your work
- Use complete cycles
- Include units
A new chart doubles its vertical drawing scale while the labelled excursion stays 0.50 L. Has the breathing depth doubled?
Give me a hint
Use the axis values rather than page height.
Compare my reasoning
- The drawing is taller because its scale changed.
- The stated volume excursion remains 0.50 L.
No; the physical depth is unchanged in the supplied values.
Look for these in your work
- Check the scale
- Reject appearance alone
Common mistakes
- Treating curve height as rate.
- Comparing traces with mismatched scales.
What can you explain now?
What changes in the supplied activity trace?
Compare with the explanation
Greater excursion and shorter cycles
Both depth and rate increase.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Read both excursion and cycle duration before describing an activity effect.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.