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.
Spirometry. One of the first pulmonary function tests is called the spirometry. This is a handy test to see the level of breathing within a person. It also measures the persons pulmonary capacity. With this test, the individual will need to place his mouth over a mouthpiece and breathe deeply into it.