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 are a group of tests that measure how well the lungs take in â¦ and release air and how well they move oxygen into the blood.   Nothing you can do in advance of a test can change this. Answered.