From the Guidelines
Pulmonary function is assessed through laboratory tests including spirometry, lung volumes, and diffusion capacity.
Key Tests
- Spirometry: measures lung function by assessing the volume and speed of air inhaled and exhaled by the lungs 1
- Lung Volumes: measures the amount of air in the lungs after maximum inhalation and exhalation 1
- Diffusion Capacity: measures the ability of the lungs to transfer gases from the air into the bloodstream, typically using carbon monoxide diffusing capacity (DL,CO) 1
Test Order and Considerations
The order of testing should be kept constant to avoid introducing variability to test results, and should consider the potential effect of one test on the subsequent test 1. For example, bronchodilator administration may affect static lung volumes and diffusing capacity measurements 1.
Standardization and Interpretation
Standardized reporting of pulmonary function tests is recommended, including the use of reference equations and quality grading 1. Interpretation of test results should begin with a review and comment on test quality, and should identify any problems or sources of variation in lung function testing 1.
From the Research
Laboratory Tests for Pulmonary Function
The following laboratory tests are used to assess pulmonary function:
- Spirometry: measures lung function, specifically the volume and speed of air that can be inhaled and exhaled 2, 3, 4
- Plethysmography: measures lung volume and can assess lung hyperinflation and pulmonary emphysema 2, 4
- Carbon monoxide diffusion capacity (DLCO): measures the ability of the lungs to transfer gas from the air into the bloodstream 2, 3, 5
- Bronchodilator testing: evaluates the response to bronchodilator treatment 2
- Lung volumes: measures the total amount of air in the lungs 3
- Diffusing capacity of lung for carbon monoxide: measures the ability of the lungs to transfer gas from the air into the bloodstream 3, 5
Clinical Implications
These tests are valuable in the management of patients with suspected or previously diagnosed respiratory disease, aiding in diagnosis, monitoring response to treatment, and guiding decisions regarding further treatment and intervention 6, 3, 4, 5. The results may indicate both respiratory and nonrespiratory disorders, including helping in the diagnosis of cardiac or neuromuscular diseases 3.