Pulmonary Function Test (PFT): A Complete Guide

A Pulmonary Function Test is a non-invasive diagnostic tool that measures how well your lungs are working. It evaluates lung volume, capacity, rates of flow, and gas exchange. Doctors commonly recommend PFTs to diagnose respiratory problems, monitor chronic lung diseases, and assess the effectiveness of treatments.

In this article, we’ll dive deep into what PFT is, why it’s done, types of tests included, the procedure, risks, results interpretation, and frequently asked questions.

What is a Pulmonary Function Test?

A Pulmonary Function Test (PFT) is a group of breathing tests that provide information about how well the lungs are functioning. These tests measure:

• Lung volume: How much air your lungs can hold.

• Airflow rate: How quickly air moves in and out of your lungs.

• Gas exchange: How efficiently your lungs transfer oxygen into the blood and remove carbon dioxide.

The results of PFT help in diagnosing respiratory conditions like:

• Asthma

• Chronic Obstructive Pulmonary Disease (COPD)

• Pulmonary fibrosis

• Lung cancer-related breathing problems

• Sarcoidosis

• Interstitial lung disease

Types of Pulmonary Function Tests

PFT is not a single test but a collection of different lung function measurements. The most common include:

1. Spirometry

• The most common PFT.

• Measures how much air you can inhale and exhale, and how quickly.

• Helps diagnose asthma, COPD, and other obstructive airway diseases.

Key results include:

• FEV1 (Forced Expiratory Volume in 1 second): Amount of air exhaled in one second.

• FVC (Forced Vital Capacity): Maximum amount of air exhaled after deep inhalation.

• FEV1/FVC ratio: Determines presence of obstruction.

2. Lung Volume Measurement (Plethysmography)

• Measures the total volume of air your lungs can hold.

• Helps in diagnosing restrictive lung diseases (e.g., pulmonary fibrosis, scoliosis-related lung restriction).

3. Diffusion Capacity (DLCO Test)

• Measures how well oxygen passes from the lungs into the blood.

• Useful in diagnosing conditions like emphysema and pulmonary hypertension.

4. Peak Expiratory Flow (PEF) Test

• Measures how quickly you can blow air out of your lungs.

• Often used in asthma monitoring.

5. Six-Minute Walk Test (6MWT)

• Assesses exercise tolerance and oxygen levels during walking.

• Helpful in patients with advanced lung or heart disease.

6. Methacholine Challenge Test

• Used when asthma is suspected but not confirmed by spirometry.

• Involves inhaling methacholine, which may cause airway narrowing in asthmatic patients.

7. Arterial Blood Gas (ABG) Test

• Though not always considered a standard PFT, it measures oxygen and carbon dioxide levels in blood.

• Helps assess gas exchange efficiency.

Why is a Pulmonary Function Test done?

Doctors recommend a PFT for multiple reasons. Some of the most common include:

1. Diagnosing Lung Diseases – To confirm or rule out conditions such as asthma, COPD, emphysema, or pulmonary fibrosis.

2. Evaluating Symptoms – If you have chronic cough, shortness of breath, wheezing, or chest tightness, a PFT can help determine the underlying cause.

3. Monitoring Chronic Lung Conditions – For patients already diagnosed with a lung disease, regular PFTs help track disease progression and treatment effectiveness.

4. Pre-Surgical Evaluation – Before certain surgeries (especially involving the chest or lungs), doctors use PFTs to check lung health.

5. Workplace Safety – People exposed to harmful dust, chemicals, or fumes (miners, construction workers, factory employees) may undergo regular PFTs to monitor lung function.

How is a Pulmonary Function Test performed?

Preparation Before the Test

• Avoid heavy meals before the test.

• Do not smoke for at least 4–6 hours.

• Stop using inhalers or bronchodilators (only if advised by your doctor).

• Wear comfortable clothing.

During the Test

• You will be asked to sit comfortably.

• A clip is placed on your nose to ensure breathing happens only through your mouth.

• You breathe into a mouthpiece connected to a spirometer or other device.

• The technician will ask you to inhale deeply and exhale forcefully several times.

Duration

The entire test usually takes 30–60 minutes depending on how many tests are performed.

Risks and safety of Pulmonary Function Tests

PFTs are generally safe and non-invasive, but some people may experience:

• Dizziness or lightheadedness (from deep or rapid breathing)

• Shortness of breath during the test

• Asthma attack in sensitive patients (rare)

• Chest discomfort

People with recent heart attack, unstable angina, or severe respiratory distress should not undergo certain PFTs unless approved by a doctor.

Interpreting Pulmonary Function Test results

PFT results are compared to normal values based on your:

• Age

• Sex

• Height

• Ethnicity

Interpretation

1. Obstructive Lung Disease – If airflow is limited (low FEV1/FVC ratio). Example: asthma, COPD.

2. Restrictive Lung Disease – If lung volumes are reduced (low TLC). Example: pulmonary fibrosis, sarcoidosis.

3. Normal Results – Indicate healthy lung function.

Your doctor will analyze the patterns to determine whether your symptoms are due to obstructive, restrictive, or mixed lung disease.

Benefits of Pulmonary Function Tests

• Early detection of lung diseases

• Monitoring effectiveness of treatment

• Evaluating workplace hazards

• Helping in pre-surgical planning

• Tracking disease progression over time

When should you get a Pulmonary Function Test?

You may need a PFT if you experience:

• Persistent cough

• Wheezing

• Shortness of breath

• Frequent chest infections

• Difficulty performing physical activities

People with chronic conditions like asthma, COPD, and pulmonary fibrosis may undergo regular PFTs as part of their treatment plan.

Living with Lung Disease: The Role of PFT in management

For individuals with chronic lung disease, PFT is not just a diagnostic tool but also a monitoring and management strategy. It helps doctors:

• Adjust medications (like inhalers, steroids, or bronchodilators)

• Recommend pulmonary rehabilitation programs

• Assess need for oxygen therapy

• Plan lifestyle modifications for better breathing

Frequently Asked Questions (FAQs)

1. What does a Pulmonary Function Test measure?

PFT measures lung volume, airflow, and gas exchange to assess lung health and detect respiratory diseases.

2. Is a Pulmonary Function Test painful?

No, it is a painless and non-invasive procedure. You only need to breathe into a device as instructed.

3. How long does a PFT take?

Most tests are completed within 30–60 minutes.

4. Can I eat before a Pulmonary Function Test?

It’s best to avoid heavy meals before the test, but light food is usually allowed.

5. Are there any side effects of a PFT?

Some people may feel dizzy or short of breath temporarily, but serious side effects are rare.

6. Who should not take a PFT?

People who had a recent heart attack, severe chest pain, or are in acute respiratory distress should avoid the test unless advised by a doctor.

7. How often should I get a PFT?

If you have a chronic lung condition, your doctor may recommend it once or twice a year, or more frequently if needed.

8. Is PFT covered under health insurance?

In many cases, yes. Since it is a diagnostic test, most health insurance plans cover it, but you should confirm with your provider.

The Pulmonary Function Test (PFT) is a vital diagnostic and monitoring tool that provides valuable insights into lung health. From detecting early signs of respiratory disorders to tracking the effectiveness of treatments, PFTs play a crucial role in modern healthcare.

If you are experiencing persistent cough, wheezing, or shortness of breath, consult your doctor about whether a pulmonary function test is right for you. Early diagnosis and monitoring can help manage conditions effectively and improve quality of life.

For more information and appointments, visit: Sparsh Diagnostic Centre

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