Pulmonary function tests usually take up to 1 1/2 hours to complete, according to National Jewish Health. The length of the tests depends on the patient's medical history and the reason for conducting the tests.
Pulmonary function tests are a combination of tests designed to determine the health of the patient's lungs, states the University of Pittsburgh Medical Center. During the test, the patient breathes into machines that measure the capacity of the lungs. Because of the heavy breathing that patients must do, some people can experience dizziness or nausea. The tests are done for a variety of reasons, including preparing the patient for surgery, checking the progression of a lung disease or as a routine exam.