There are many ways in which cancer can cause fatigue. The growth of a tumor, in general, can be taxing for your body. Other symptoms of cancer such as shortness of breath, anemia, pain, or a decreased level of oxygen in your blood (hypoxia) can cause fatigue.
A pulmonary function test may take 30 to 60 minutes to complete. This will vary according to the amount of trials necessary for you to get repeatable test results.
Pulmonary function tests (PFTs) measure how well your lungs take in and exhale air and how efficiently they transfer oxygen into the blood. There are several different tests. 1  Spirometry measures how well the lungs exhale (breathe out).2  Lung volume measures how well the lungs inhale (breathe in).ulmonary function tests help: 1  diagnose diseases of the lung such as asthma, bronchitis, and emphysema. 2  determine the cause of shortness of breath. 3  measure the effects of exposure to chemicals, coal dust, and other toxins on your lung function.