2.6.4Inquiry Process
Measuring Lung Volumes- Skills — IB Biology HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 66 of 160
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 5Lung Volume Terms
Tidal volume
- Tidal volume The volume of air moved in or out of the lungs in one normal, resting breath, typically around 0.5 dm³ in an adult.
Vital capacity
- Vital capacity The largest volume of air that can be exhaled after the deepest possible inhalation, combining tidal, inspiratory reserve and expiratory reserve volumes.
Inspiratory reserve volume
- Inspiratory reserve volume The extra air that can be breathed in by forced inhalation after a normal inhalation.
Expiratory reserve volume
- Expiratory reserve volume The extra air that can be forced out after a normal exhalation.
Residual volume
- Residual volume The air that stays in the lungs and airways after maximum exhalation, which cannot be measured directly with a spirometer.
Section 2 of 5Using a Spirometer or Data Logger
Skills questions test reading and processing a trace.
1
A spirometer or a breathing sensor records changes in volume of air as the person breathes through a mouthpiece.
2
The trace rises and falls with each breath, and the height of one cycle shows the tidal volume.
3
A deep breath in followed by a full breath out is recorded to find the vital capacity.
4
Counting the peaks over a known time gives the breathing rate in breaths per minute.
5
Repeating measurements and averaging them improves reliability; safety rules include clean mouthpieces and stopping if the person feels dizzy.
Section 3 of 5Ventilation Rate and Exercise
Ventilation Rate and Exercise
Ventilation rate
- Ventilation rate Ventilation rate in dm³ per minute equals tidal volume multiplied by the number of breaths per minute.
Effect of exercise
- Effect of exercise Exercise raises both tidal volume and breathing rate because muscles need more oxygen and produce more carbon dioxide.
Control
- Control Chemoreceptors detect rising carbon dioxide and falling pH, and the brainstem increases signals to the breathing muscles.
Fitness
- Fitness Trained individuals often have larger vital capacities and lower resting breathing rates.
| Measure | Resting example | Hard exercise example |
|---|---|---|
| Tidal volume (dm³) | 0.5 | 2.0 |
| Rate (breaths/min) | 12 | 30 |
| Ventilation (dm³/min) | 6 | 60 |
Section 4 of 5Worked Example
Question
- A student has a tidal volume of 0.45 dm³ at rest and breathes 14 times per minute.
- During exercise tidal volume is 1.8 dm³ at 28 breaths per minute.
- Calculate the percentage increase in ventilation rate.
- Resting ventilation = 0.45 × 14 = 6.3 dm³/min.
- Exercise ventilation = 1.8 × 28 = 50.4 dm³/min.
- Increase = 50.4 − 6.3 = 44.1 dm³/min.
- Percentage increase = 44.1 ÷ 6.3 × 100 = 700%.
Answer Ventilation rate rises from 6.3 to 50.4 dm³/min, an increase of 700%.
Section 5 of 5Exam Checklist & Tips
2.6.4 – Key Points for the Exam
- Tidal volume The volume of air inhaled or exhaled in one normal breath.
- Vital capacity The maximum volume that can be exhaled after a maximal inhalation.
- Residual volume Air remaining in the lungs after the strongest possible exhalation.
- Ventilation rate The volume of air moved in or out of the lungs per minute.
Common Mistakes
- Giving ventilation rate in breaths per minute;
- it is a volume per minute, while breaths per minute is breathing rate.
- Reading tidal volume from the highest peak on a trace instead of from a normal breath.
- Including residual volume in vital capacity; it is not exhaled.
- Forgetting units, such as dm³ or cm³, when answering calculations.
Last updated:
\n