Measuring lung volumes

1. Measuring lung volumes

2. Syllabus reference: • outline the mechanism of breathing in mammals, with reference to the function of the rib cage, intercostal muscles and diaphragm • explain the meanings of the terms tidal volume and vital capacity • describe how a spirometer can be used to measure vital capacity, tidal volume, breathing rate and oxygen uptake • analyse and interpret data from a spirometer

3. Inspiration & expiration

4. Inspiration & expiration

5. residual volume Lung volumes

6. Lung volumes • The maximum volume of the lungs is about 5dm3 (5 litres) although we never completely empty the lungs; even if we breathe out as much as possible (expiratory capacity) there will still be about 1.5 dm3 left in the lung (residual volume). • The amount of air breathed in and out at each breath is called the tidal volume. At rest this will be around 0.5 dm3, rising to about 2.5 dm3 when we are breathing very deeply. • The maximum volume that can be exchanged by breathing in as much as possible and then forcing out as much as possible is our vital capacity.

7. The spirometer oxygen

8. Spirometer

9. Lung volumes Note: compare to ‘inverted’ trace in textbook

10. Lung volumes

11. oxygen The spirometer

12. Lung volumes; definitions maximum inspiration Inspiratory capacity Inspiratory reserve volume Inspiratory reserve volume Vital capacity Vital capacity Volume in dm3 inspiration at rest inspiration at rest Tidal volume Tidal volume Expiratory capacity Expiratory capacity expiration at rest expiration at rest Expiratory reserve volume Expiratory reserve volume maximum expiration maximum expiration Total lung capacity Total lung capacity Residual volume Residual volume