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.
Unlike some tests, pulmonary function testing is highly dependent on the efforts of the patient and the technician performing the test. Pulmonary function testing can be considered to be several tests in one. The primary factors that determine what is normal for a given pulmonary function measurement are Age, Height and Gender.