How the lung is measured: the volumes and capacities a spirometer can record, the flow tests that expose airway obstruction, and the tests of gas exchange and pulmonary circulation behind them. Your book says long questions are rare here, though one does come — describe the principle, methods and merits of the various lung function tests. Short notes on lung volumes and capacities are the most repeated item in this chapter, followed by compliance, airway resistance and timed vital capacity, and the obstructive-versus-restrictive comparison is the favourite essay. Viva is mostly lists: classify the tests, name their uses, quote the normal values, give the features of each disease pattern.
Topics, in the book’s order
- Lung volumes, capacities and spirometry · pp. 965–967 · asked 16 times
- Obstructive vs restrictive disease · pp. 967–969 · asked 4 times
- Tests of gas exchange and pulmonary circulation · pp. 969–971
When you’ve read them: Quiz 114 · Pulmonary Function Tests, 15 questions.
After this chapter you should be able to
- classify pulmonary function tests, and say what they are used for
- quote the normal values of the PFT parameters
- define each lung volume and capacity, and give its normal value
- draw the FEV₁ curves of a normal, an obstructive and a restrictive lung
- explain the physiological basis of each test — what it actually measures
- read a PFT report and say which pattern of disease it shows
Going further: the principle, procedure, application and advantage of each individual test, from the spirometer to the Swan–Ganz catheter.
Viva checklist
- Classify PFTs; name the tests of ventilation, of gas exchange and of pulmonary circulation
- The uses of PFTs, and the normal values of the main parameters
- Define TV, IRV, ERV, RV, VC, IC, FRC and TLC, with values for men and women
- VC against FVC, and why FVC is the one used in disease
- Which volumes and capacities a spirometer cannot measure, and how they are measured instead
- Compliance: its definition, what a high or low value means, and the conditions that lower it
- Airway resistance and the conditions that raise it; conditions that lower vital capacity
- Timed vital capacity: what fraction of FVC leaves in one, two and three seconds
- MMFR, FEF200–1200, PEFR and MVV — which airways or function each reports on
- Features of obstructive disease, features of restrictive disease, and the one ratio that separates them
- Common obstructive diseases; parenchymal and extraparenchymal restrictive diseases
- Hypoxemia: what it is, when it occurs, and the conditions that alter diffusing capacity
- Methods of sampling alveolar air and expired air; the normal V/Q ratio and the nitrogen washout test
- The A–aO₂ gradient, its normal value, the one cause that leaves it normal, and what raises PVR