Pulmonary Function Test (PFT)

Pulmonary function tests measure how well the lungs move air and exchange gases. They are used to diagnose and monitor asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, and other respiratory conditions. Doctors may also order PFTs before surgery to assess anesthetic risk or to monitor the impact of medications and rehabilitation programs.

• Avoid heavy meals, smoking, or vigorous exercise for 4–6 hours before the test.
• Certain medications (such as inhaled bronchodilators) may need to be withheld for a period of time, depending on your doctor’s instructions.
• Wear loose, comfortable clothing that does not restrict breathing.
• Tell your provider if you have had recent respiratory infections, chest pain, or surgeries.

You will breathe into a mouthpiece connected to a machine called a spirometer. Different maneuvers are performed, such as inhaling deeply and exhaling forcefully, or breathing normally while measurements are taken.

Additional tests may include:

• Lung volumes (measuring total air capacity).
• Diffusion capacity (how well oxygen passes from lungs into blood).
• Bronchodilator testing (before and after inhaled medication to assess reversibility of airway obstruction).
• The entire testing session typically takes 30-60 minutes.

• PFTs are very safe and noninvasive.
• Some patients may feel lightheaded, short of breath, or tired during testing.
• Rarely, the maneuvers may temporarily trigger asthma symptoms or coughing.

Results are expressed as percentages compared to predicted values for your age, sex, height, and ethnicity. Patterns such as obstructive (asthma, COPD) or restrictive (pulmonary fibrosis, chest wall disease) may be identified. Your doctor will explain how results relate to your symptoms and treatment plan.