Pulmonary Function Test

Pulmonary function tests (PFTs) are a group of breathing tests that show how well your lungs move air and how efficiently they deliver oxygen to the body. Spirometry is the most common PFT and measures how much air you inhale and exhale and how quickly you can blow air out.

Healthcare providers order PFTs to diagnose asthma, chronic obstructive pulmonary disease (COPD), restrictive lung disease, and to monitor lung health during treatment or before surgery. The tests are safe, noninvasive, and usually take less than 30 minutes.

• Lung volumes: Total amount of air in your lungs after inhaling deeply
• Airflow: How quickly air moves out of the lungs (forced expiratory volume, or FEV1)
• Gas exchange: How well oxygen moves into the bloodstream (diffusing capacity)
• Airway responsiveness: How airways react to inhaled medications or triggers

1. Follow Instructions:
   • Avoid caffeine, alcohol, and heavy meals for a few hours before testing if advised
   • Wear comfortable clothing that does not restrict breathing
2. Medications:
   • Your provider may ask you to hold certain inhalers or bronchodilators before the test
   • Bring all current inhalers or medications to the appointment
3. Smoking:
   • Do not smoke for at least 1 hour before the test (longer if possible)
4. Health Status:
   • Tell the technician if you have recently had chest pain, surgery, or a respiratory infection

1. Spirometry:
   • You will sit upright and wear a nose clip to ensure air exits only through your mouth
   • You will inhale deeply and blow into a mouthpiece as hard and fast as possible for several seconds
   • The test may be repeated several times for accuracy
2. Bronchodilator Testing:
   • Sometimes, you inhale a bronchodilator medication and repeat the test to see if lung function improves
3. Lung Volume Tests:
   • You may sit inside a clear booth (plethysmography) or breathe a special gas mixture to measure lung volumes
4. Diffusing Capacity (DLCO):
   • You inhale a small amount of carbon monoxide (safe concentration) to assess how well oxygen crosses into the blood

Pulmonary function tests are generally safe. You may feel lightheaded, cough, or feel short of breath briefly after blowing hard. Tests may be postponed if you have a current respiratory infection, uncontrolled high blood pressure, or recent eye, chest, or abdominal surgery.

• FEV1 and FVC (forced vital capacity): Indicate airway obstruction or restriction
• FEV1/FVC ratio: Helps distinguish obstructive (asthma, COPD) from restrictive lung disease
• Diffusing capacity (DLCO): Low values can signal emphysema, pulmonary fibrosis, or anemia
• Peak expiratory flow: Shows how fast you can exhale and is useful for asthma monitoring

Results are compared to predicted values based on your age, sex, height, and ethnicity. Your provider interprets the findings and combines them with symptoms and imaging to make a diagnosis or adjust treatment.

• Schedule repeat testing to monitor chronic lung conditions or response to medications
• Use results to update your asthma or COPD action plan
• Seek medical attention if breathing symptoms worsen, despite normal test results

Pulmonary function tests give valuable information about lung health and help guide treatment decisions for many respiratory conditions.