Pulmonary function tests are a group of tests that measure how well the lungs take in and release air and how well they move gases such as oxygen from the atmosphere into the body’s circulation. Spirometry measures airflow. By measuring how much air you exhale and how quickly, spirometry can evaluate a broad range of lung diseases. For some of the test measurements, you can breathe normally and quietly. Other tests require forced inhalation or exhalation after a deep breath. Sometimes you will be asked to inhale the substance or a medicine to see how it changes your test results.
To measure diffusion capacity, you breathe a harmless gas, called a tracer gas, for a very short time. The concentration of the gas in the air you breathe out is measured. The difference in the amount of gas inhaled and exhaled measures how effectively gas travels from the lungs into the blood. This test allows the doctor to estimate how well the lungs move oxygen from the air into the bloodstream
Pulmonary function tests are done to:
- diagnose certain types of lung disease (such as asthma, bronchitis, and emphysema)
- find the cause of shortness of breath
- measure whether exposure to chemicals affects lung function
- check lung function before someone has surgery
It also can be done to assess the effect of medication or measure progress in disease treatment.