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.
Lung function tests (also called pulmonary function tests) assess how well your lungs work. These tests measure: 1  how quickly you can move air in and out of your lungs. 2  how much air they can hold. 3  how well they transfer oxygen into, and remove carbon dioxide from, your blood.