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. Pulmonary function tests are a group of tests that measure how well your lungs work. This includes how well you are able to breathe and how well your lungs are able to supply oxygen to the rest of your body. Your doctor may order these tests: 1  if you are having symptoms of lung problems. 2  as part of a routine physical.