Lung Function Tests
Lung function tests are a group of diagnostic procedures used to measure how well your lungs work and to monitor various respiratory conditions.
Overview
Lung function tests, also called pulmonary function tests or PFTs, check how well your lungs are working. They are often used alongside other information to diagnose and monitor lung diseases. Most tests involve breathing through a mouthpiece connected to a device that measures:
- How much air your lungs can hold
- How well you move air in and out of your lungs
- How well your lungs absorb oxygen from the air and move it into your blood
These tests also assess the health of your airways, including your nose, throat, trachea (windpipe), and bronchial tubes.
Common Lung Function Tests
- Spirometry: The most common test, which measures how much air you breathe out and how fast you can blow it out.
- Lung volume test (body plethysmography): The most accurate way to measure the total amount of air your lungs can hold and the air remaining after you exhale.
- Lung diffusion capacity test: Measures how effectively your lungs deliver oxygen to your blood.
- Exercise tests: These measure lung function during activity, such as the six minute walk test or the cardiopulmonary exercise test (CPET).
Uses and Indications
Lung function tests are used to:
- Diagnose and monitor diseases such as asthma, COPD, emphysema, pulmonary fibrosis, and pulmonary hypertension.
- Guide treatment decisions for lung conditions.
- Monitor diseases that affect the lungs, such as scleroderma or sarcoidosis.
- Assess lung function before surgery or check for damage from chemical exposure.
You may need testing if you experience symptoms like shortness of breath, wheezing, coughing, chest tightness, or if you have an abnormal chest x-ray.
Preparation and Risks
To ensure accurate results, wear loose clothing and avoid large meals, heavy exercise, smoking, alcohol, and caffeine before the test. If you use inhaler medicines, consult your provider about whether to stop them temporarily. There is very little risk, though some may feel lightheaded, dizzy, or tired from breathing hard.
Understanding Results
Results are compared to healthy individuals of the same height, sex, and age. Abnormal results generally fall into two categories:
- Obstructive lung conditions: Airways are narrowed, making it hard for air to flow out (e.g., asthma, bronchitis, emphysema).
- Restrictive lung conditions: The lungs or chest muscles cannot expand fully, decreasing the amount of air the lungs can hold (e.g., scleroderma, sarcoidosis, pulmonary fibrosis).