Pulmonary Function Testing
Pulmonary function testing (PFT) is a group of tests that measure how well the lungs are working. These tests assess lung volume, capacity, rates of flow, and gas exchange. This information helps healthcare providers diagnose and decide the treatment of certain lung disorders.
There are several components of pulmonary function tests:
This is the most common PFT. It measures how much air a person can inhale and exhale, and how quickly they can exhale. The person breathes into a mouthpiece connected to a spirometer. It measures forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). FVC is the total amount of air exhaled during the test, while FEV1 is the amount of air exhaled in the first second. These values are used to identify conditions like asthma and chronic obstructive pulmonary disease (COPD).
This test measures how well the lungs transfer oxygen from the air into the blood. The person breathes in a harmless gas mixture, and the test measures how much of the gas is absorbed into the bloodstream. A reduced DLCO can indicate diseases affecting the lung’s blood vessels or the alveolar walls, such as pulmonary fibrosis or emphysema.
Understanding lung volumes is crucial in PFTs as they help in diagnosing and managing lung diseases. Lung volumes include:
- Total Lung Capacity (TLC): The total volume of the lungs, calculated as the sum of all lung volumes.
- Vital Capacity (VC): The total amount of air that can be exhaled after a maximal inhalation
- Inspiratory Capacity (IC): The total amount of air that can be inhaled after a normal exhalation
- Functional Residual Capacity (FRC): The amount of air remaining in the lungs after a normal exhalation
These volumes and capacities provide a detailed picture of lung function. For example, in obstructive lung diseases like COPD, the residual volume and functional residual capacity may be increased due to air trapping. In restrictive lung diseases like pulmonary fibrosis, total lung capacity and vital capacity are often reduced due to lung stiffness.
Pulmonary function tests are important diagnostic tools for a variety of lung conditions. The results are compared to normal values based on age, height, sex, and ethnicity. Abnormal results can indicate obstructive diseases (like asthma or COPD), restrictive diseases (like pulmonary fibrosis), or other pulmonary conditions. These tests are usually safe, but patients may feel tired afterward, and some may experience shortness of breath or dizziness during the tests.
