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, thus representing an important adjunct to the patient history, various lung imaging studies and invasive testing such as bronchoscopy and open-lung biopsy. Insight into underlying pathophysiology can often be gained by comparing the measured values for pulmonary function tests obtained on a patient at any particular point with normative values derived from population studies. Diseases such as asthma, emphysema, chronic bronchitis, and pulmonary fibrosis can be identified and optimal treatment regimens derived and monitored.

Practicing clinicians must become familiar with pulmonary function testing because it is often used in clinical medicine for evaluating respiratory symptoms such as dyspnea and cough, for stratifying preoperative risk and for diagnosing common diseases such as asthma and chronic obstructive pulmonary disease. The percentage of predicted normal is used to grade the severity of the abnormality.

Pulmonary Function Testing has been a major step forward in assessing the functional status of the lungs as it relates to:

1. How much air volume can be moved in and out of the lungs
2. How fast the air in the lungs can be moved in and out
3. How stiff are the lungs and chest wall – a question about compliance
4. The diffusion characteristics of the membrane through which the gas moves (determined by special tests)
5. How the lungs respond to chest physical therapy procedures

The primary instrument used in pulmonary function testing is the spirometer. It is designed to measure changes in volume and can only measure lung volume compartments that exchange gas with the atmosphere.

Do not eat a heavy meal before the test. Do not smoke for 4 – 6 hours before the test. You’ll get specific instructions if you need to stop using bronchodilators or inhaler medications. You may have to breathe in medication before the test. Occasionally, if exercise-induced asthma is suspected, Dr. Weinstein may have you perform a spirometry after exercising in the human performance lab.