Spirometer Virtual Lab: Lung Volumes and Ventilation Rate

This spirometer virtual lab covers the lung volume measurements of IB, A-level and IGCSE Biology. Students breathe into a virtual spirometer, read tidal volume, inspiratory and expiratory reserve volumes and vital capacity from the trace, and calculate pulmonary ventilation at rest and during exercise. They then compare healthy lungs with asthma and finish with the limewater test on inhaled and exhaled air. Nobody shares a mouthpiece, and every number below was read from the simulation.

Curriculum links

• IB Biology B3.1 (gas exchange): measurement of lung volumes, including tidal volume, vital capacity and the reserve volumes, and the ventilation rate.
• AQA A-level Biology 7402, section 3.3.2: pulmonary ventilation = tidal volume × ventilation rate, and interpreting spirometer data, including lung disease.
• Cambridge IGCSE Biology 0610, topic 11.1: the effect of physical activity on the rate and depth of breathing, and limewater as a test for carbon dioxide in inspired and expired air.

Simulic is not affiliated with or endorsed by the IB, AQA or Cambridge.

Before the lab (5 min)

Ask: "A healthy student goes from rest to moderate exercise. What happens to their tidal volume and their breathing rate?" On a class link this is question 1; the simulation unlocks after students answer.

Method in the simulation

1. Open the Spirometer tab. Set Lungs to Healthy, leave Smoker unticked and set Activity to Rest.
2. Wait for three quiet breaths. The line under the trace then shows the tidal volume (TV), the breathing rate and the pulmonary ventilation.
3. Press Breathe in fully, then out fully (VC). When the buttons work again, press Forced expiration (FEV₁), then Record results. Copy IRV, ERV and VC from the line under the trace.
4. Set Activity to Moderate exercise and repeat steps 2–3, then Vigorous exercise.
5. Set Lungs to Asthma (bronchoconstriction) and Activity to Rest, and repeat.

Person	Rate (per min)	TV (L)	Ventilation (L/min)	IRV (L)	ERV (L)	VC (L)	FEV₁/FVC (%)
Healthy, rest
Healthy, moderate
Healthy, vigorous
Asthma, rest

Expected results

Each spirometer reading carries a random error of a few percent, so the values are ranges from several browser runs.

Person	Rate	TV (L)	Ventilation (L/min)	IRV (L)	ERV (L)	VC (L)	FEV₁/FVC
Healthy, rest	14	0.49–0.52	6.8–7.2	3.0–3.2	1.2	4.67–4.87	81–82 %
Healthy, moderate	22	1.58–1.64	34.7–35.8	2.3–2.4	0.8	4.68–4.80	82–83 %
Healthy, vigorous	31	2.50	77.0	1.5–1.6	0.7	4.80–4.84	81 %
Asthma, rest	20	0.44–0.46	8.8–9.2	2.8–2.9	0.9	4.13–4.21	60 %

• Exercise raises both depth and rate: ventilation rises about five times from rest to moderate exercise. Vital capacity stays the same; the extra tidal volume comes out of the reserve volumes.
• Asthma barely changes VC, but FEV₁ falls to 2.3–2.5 L, so FEV₁/FVC drops to 60 %: the obstructive pattern. With vigorous exercise the sim reports that the body needs 92 L/min but the lungs can ventilate only 71 L/min.
• A healthy smoker gave FEV₁/FVC = 76 %.

Questions for students

1. (Prediction, asked again after the lab) From rest to moderate exercise, what happens to tidal volume and breathing rate?
2. Which settings must stay the same while you compare rest and exercise?
3. What is the vital capacity of the healthy person at rest?
4. How many times greater is the ventilation in moderate exercise than at rest?
5. Explain why tidal volume and breathing rate both increase during exercise.

Answers for teachers: (1) Both increase. (2) Lungs (Healthy) and Smoker (unticked); only Activity changes. (3) Accept 4.6–5.0 L. (4) Accept 4.5–5.5; most groups get about 5. (5) Contracting muscles respire faster, so they need more oxygen and make more carbon dioxide. Deeper, faster breathing raises the ventilation, keeping the concentration gradients in the alveoli steep.

Common misconceptions

• "Vital capacity grows during exercise." VC stays the same; the tidal volume takes up more of it.
• "Breathing out always uses muscles." Quiet expiration is elastic recoil. Only forced expiration uses the internal intercostal and abdominal muscles.
• "Asthma makes the lungs smaller." VC hardly changes. Air leaves slowly through narrowed airways, so FEV₁ falls.
• "Exhaled air is mostly carbon dioxide." The sim's table shows about 4 % CO₂ and 16 % O₂ in exhaled air.

Extension

• Limewater practical: open Limewater practical, choose a Speed of ×30 and press Start breathing. At rest, tube B (exhaled air) turned milky after 21–23 s, while tube A (inhaled air) was still clear after 900 s. After moderate exercise tube A turned milky after 613–648 s; after vigorous exercise, after 295–314 s.
• Bell jar model: on Breathing mechanics, switch Model to Bell jar and list what the model cannot show.

FAQ

Can the class link open on the spirometer?

Yes. On the Share page, pin Screen to "Spirometer" in the link's starting values. You can also pin Lungs, Smoker and Activity. Otherwise step 1 tells students to open the tab.

Why are the VC buttons greyed out?

The spirometer is recording a breath. Wait until the trace returns to quiet breathing; a button pressed during a recording is ignored.

Can students measure the residual volume?

No. A spirometer only records air moving in and out, so the residual volume (RV) on the trace is an estimate, as the note under the sim explains.

Related simulations and guides

Circulatory and respiratory systems – heart rate during activity Cellular respiration pathway – glycolysis, link reaction, Krebs cycle, electron transport chain and fermentation

For carbon dioxide and other gas tests, see the gas tests virtual lab. To measure respiration itself, see the respirometer virtual lab.