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Pulmonary Function Test (PFT) or Spirometry

Reviewed by Dr. Smaran Cladius, MD Respiratory Medicine

Pulmonary Function Test (PFT)

Pulmonary Function Test (PFT) or Spirometry is used for diagnosis of Asthma, COPD and Interstitial Lung diseaes. This non-invasive diagnostic tool is the gold standard for measuring how well your lungs are working.

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Spirometry test to check breathing function

What is a Pulmonary Function Test (PFT)?

Doctor explaining pulmonary function test to patient

A Pulmonary Function Test is a series of breathing tests used to evaluate how much air your lungs can hold, how quickly you can move air in and out, and how well your lungs put oxygen into your blood.

Unlike an X-ray or CT scan, which shows the structure of your lungs, a PFT shows how your lungs function in real-time.

Why is a PFT Performed?

Doctors use PFTs to diagnose various respiratory conditions and monitor the effectiveness of treatments. Common reasons include:

Specialist analyzing PFT results

  • Diagnosing Lung Diseases: Identifying conditions such as Asthma, COPD (Chronic Obstructive Pulmonary Disease), Emphysema, or Pulmonary Fibrosis.

  • Investigating Symptoms: Finding the cause of unexplained breathlessness or chest tightness.

  • Surgical Clearance: Assessing if a patient’s lungs are strong enough to undergo surgery.

  • Monitoring Treatment: Checking if medications (like inhalers) are improving lung function over time.

  • Occupational Health: Screening for lung damage caused by exposure to chemicals or dust in the workplace.

Common Types of PFT Measurements

During a PFT session, you may perform several different breathing maneuvers. The most common measurements include:

Medical consultation for lung function diagnosis

1. Spirometry

This is the most frequent PFT. You breathe into a mouthpiece connected to a device called a spirometer. It measures:

  • FVC (Forced Vital Capacity): The total amount of air you can exhale forcefully after taking a deep breath.

  • FEV1 (Forced Expiratory Volume): The amount of air you can push out in the first second of a forceful exhale.

2. Lung Volume Testing (Plethysmography)

This test measures the total volume of air in your lungs, including the air that remains after you exhale as much as possible (residual volume). This is often done inside a clear, booth-like chamber.

3. Diffusion Capacity (DLCO)

This measures how effectively your lungs transfer oxygen from the air sacs into the bloodstream. It involves breathing in a tiny, safe amount of a tracer gas and holding your breath for a few seconds.

What to Expect During the Procedure PFT

Pulmonary function test measuring lung capacity

A PFT is safe and painless, though it does require some physical effort.

  • The Equipment: You will wear a nose clip to ensure all air goes through your mouth. You will blow into a sterile mouthpiece connected to a computer.

  • The Coach: A technician will "coach" you through the breathing patterns, often shouting instructions like "Blow, blow, blow!" to ensure you give your maximum effort.

  • Duration: A full battery of PFTs typically takes between 30 and 45 minutes.

  • Bronchodilator Challenge: In some cases, the test is repeated after you use an inhaler to see if your lung function improves with medication.

How to Prepare for Your PFT

medical consultation

To get the most accurate results, follow these preparation tips:

  • Medication: Ask your doctor if you should stop using your "rescue" or "maintenance" inhalers before the test.

  • Smoking: Do not smoke for at least 6 to 12 hours before the test.

  • Large Meals: Avoid eating a heavy meal right before the appointment, as a full stomach can make it harder for your lungs to expand fully.

  • Clothing: Wear loose-fitting clothes that do not restrict your chest or abdomen.

  • Exercise: Avoid strenuous exercise for several hours before the test.

Understanding Your Results

Patient performing PFT for lung evaluation

Your results are compared to "predicted values" based on your age, height, gender, and ethnicity.

  • Obstructive Pattern: Suggests the airways are narrowed (common in Asthma or COPD).

  • Restrictive Pattern: Suggests the lungs cannot expand fully (common in Pulmonary Fibrosis or chest wall issues).

Summary

A Pulmonary Function Test is a vital step in managing your respiratory health. By providing precise data on your lung capacity and efficiency, it allows your medical team to tailor a treatment plan specifically for you.

Is it time for a lung check-up? If you are a current or former smoker, or if you struggle with daily activities due to breathing, talk to a pulmonologist about scheduling a PFT.

Research & Publications

Dr. Cladius has published research on Pleural Effusion

1. Study of Pulmonary Function Tests in Steel Plant Workers

2. A Study to Compare Lung Function Test in Cigarette and Bidi Smokers with Non-Smokers

Journal of Preventive Medicine and Holistic Health, 2015

Journal of Datta Meghe Institute of Medical Sciences University, 2015

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About the Service Provider

Dr. Smaran Cladius - MD Respiratory Medicine, Fellowship in Interventional Pulmonology, Certificate in Allergy Testing & Allergen Immunotherapy 

Pulmonologist | Chest Physician | Allergy & Sleep Specialist

Dr. Smaran Cladius is a pulmonologist specializing in the diagnosis and management of respiratory diseases, including chronic cough, asthma, COPD, respiratory allergies, tuberculosis, interstitial lung diseases and sleep-related breathing disorders.

Medically reviewed and Last updated: July 2026

This information is for general educational purposes only and is not a substitute for professional medical advice. Read our full Medical Disclaimer →

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