28. Functional pulmonary diagnostics – spirometry, diffusion capacity, lung volumes, bodyplethysmography, cardio-pulmonary exercise tests.

Functional pulmonary diagnostics – spirometry, diffusion capacity, lung volumes, body plethysmography, cardio–pulmonary exercise tests

• A group of tests that measure:
• How well lungs take in and release air
• How well lungs move gases from the air to the body
• The tests are used to:
• Check disease states/progress
• Baseline lung operations
• Test in people having surgery

Spirometry

• Used to assess the mechanical function of the lungs, chest wall and respiratory muscles
• Patients take the deepest breath possible and then exhales into a sensor as hard as possible for as long as possible (usually at least 6 seconds)
• Spirometry provides the following values:
• Vital capacity = tidal volume + IRV + ERV
• ~ 4.8 - 5.6 L
• Forced vital capacity
• Forced expiratory volume
• Forced expiratory flow
• Used in assessing breathing patterns for:
• Obstructive asthma
• Obstructive COPD
• Pulmonary fibrosis

Lung volumes

• Used in evaluation of suspected restrictive lung disease and evaluation of hyperventilation
• Lung volumes provide the following values
• Functional residual capacity = remaining air after normal expiration = 2 - 3 L
• Total lung capacity = vital capacity + residual volume = 6-7 L
• Residual volume = air in lungs after max forced expiration that can’t be mobilised
• Used in:
• Emphysema
• Restrictive lung disease