Spirometry is a test that measures the capacity of the lungs. In many respiratory diseases, the passageways to lungs become narrow and you are not able to breathe properly. Spirometry measures how fast your lungs are filled with air and how fast they get empty.

You need to sit while performing the spirometry test. Take a full breath in and blow out completely into a tube which is attached to the spirometer. Measurements by the spirometer machine indicate your lung capacity. The test is done three times. When the test is performed to check the efficacy of drugs on your lungs, your doctor may ask you to take the medication few hours before the test.

The doctor will recommend spirometry test as a part of diagnosis and follow up of the following lung conditions: asthma - swelling and narrowing of airways; chronic obstructive pulmonary disease (COPD) - narrowing of airways due to lung problems; cystic fibrosis - clogging of lungs due to mucus; pulmonary fibrosis - scarring on the lung tissues which reduces the oxygen-carrying capacity.

No, the spirometry test is not at all painful. A laboratory technician helps you to carry out the test. On some occasions, the test might be tiring for some individuals. But overall, the test is simple and easy and causes no pain to people performing it.

You need the following preparation for spirometry: do not eat heavy meals before the test; do not drink alcohol before the test; do not smoke an hour before the test; your doctor will advise whether to take drugs which widen your airways or avoid them before the test as they may interfere with the test results; wear loose fitting clothes; and avoid strenuous exercise.