Spirometry is the most common lung function test. It measures the amount and speed of the air that can be blown out of the lungs in one strong respiratory breath. It is simple and very safe to perform, but requires cooperation and effort from the individual tested. It can usually be performed in children over 5 years old.
Frequently, it is used to detect airflow obstruction, which is a characteristic of certain lung diseases, such as asthma and chronic obstructive pulmonary disease. In these diseases, assessing lung function with spirometry is important for diagnosis and monitoring, as recommended by most guidelines. Spirometry can also be used when testing the reversibility of the airways to a bronchodilator drug.
The test consists of blowing through a tube, with a clip in your nose, both as fast and strong as possible. The test is not painful at all, and it is usually repeated at least three times. If the manoeuvres are not good enough, it is recommended to repeat the effort until three manoeuvres are reproducible, that is, with similar results. This can be quite tiring, especially if the patient is not in a good condition.
The medication used for asthma may change the results of the test. If you are scheduled for a hyperreactivity test you should ask your doctor if you must withdraw the medication. The doctor might want to know the result of the test with no modification by the medication, but might also want to know if the medication is protecting you.