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 breathing and how well the lungs are functioning. Spirometry measures airflow. By measuring how much air you exhale, and how quickly you exhale, spirometry can evaluate a broad range of lung diseases. In a spirometry test, while you are sitting, you breathe into a mouthpiece that is connected to an instrument called a spirometer.