Pulmonary function tests are essentially breathing tests which may be used for obtaining the following information as well as in evaluating your ability to undergo surgical procedures:

• important baseline information for people over age 40, especially for smokers and people who have been exposed to environmental hazards

• to help diagnose and evaluate lung disease

• to determine your response to and the effectiveness of specific treatments

• to measure the severity of lung disease or injury and to monitor the course of a lung illness and therapy.

Also called ventilation tests, a pulmonary function test uses a piece of equipment called a spirometer or peak flow meter to measure both the amount and speed of air as it is forcefully exhaled from the lungs. Additional equipment may be used for variations on the basic ventilation test. One is called a spirogram, in which the patient blows into the testing apparatus as rapidly and as hard as possible for as long as possible. Usually, the test is conducted twice to ensure good results. This test is helpful in diagnosing obstructive airway disease, such as asthma, in which a bronchodilator medication may be given to the patient to see if breathing improves. Other pulmonary tests include lung volume determinations, in which a specially mixed gas is inhaled and then slowly exhaled, and a diffusion capacity test, in which another specially mixed gas is inhaled and then released and measured.

Arterial blood gas studies are another type of pulmonary function test, that use a sample of blood to measure how well oxygen is being delivered to the body’s tissues and carbon dioxide removed. 

These tests can be performed in the doctor’s office or an outpatient clinic. Be sure to tell your doctor beforehand if you have every been told that you have any of the following conditions or if you are taking any medications prescribed by a different doctor:

• heart disease, particularly chest pain referred to as angina

• any other chest or lung condition

• allergies to any medications.

Additionally, prior to a pulmonary function test, it is usually recommended that a patient follow specific restrictions for a certain period of time. These may include the following: 

• avoid eating a heavy meal or solid food for 4 to 6 hours before the test.

• avoid smoking for 4 hours bef