The Complete Guide to Pulmonary Function Tests: Preparing, Procedure, and Results

Feb 20, 2025

Pulmonary Function Tests (PFTs) are essential diagnostic tools used to assess lung function and detect respiratory disorders. Whether you are experiencing breathing difficulties, have a history of lung disease, or need a test for occupational health, understanding PFTs can help you prepare and interpret the results. This guide will walk you through what PFTs are, their importance, how to prepare, what to expect during the procedure, and how to understand the results.

What is a Pulmonary Function Test?

Pulmonary Function Tests (PFTs) are a group of non-invasive tests that measure how well your lungs are working. They evaluate lung volume, capacity, airflow, and gas exchange, helping doctors diagnose and monitor conditions like asthma, chronic obstructive pulmonary disease (COPD), and other respiratory disorders.

Why Are Pulmonary Function Tests Important?

• Early Diagnosis: Helps detect lung diseases before symptoms become severe.
• Monitoring Conditions: Assists in tracking progression in diseases like COPD and asthma.
• Treatment Planning: Helps doctors determine the effectiveness of treatments and medications.
• Pre-Surgical Assessment: Evaluates lung function before surgeries that may impact breathing.
• Occupational Health:
  Ensures lung safety in workplaces exposed to chemicals or pollutants.

Preparing for a Pulmonary Function Test

Proper preparation ensures accurate test results. Here’s how you can prepare:

Before the Test:

• Avoid Smoking: Refrain from smoking at least 24 hours before the test.
• Stop Certain Medications: Consult your doctor about stopping bronchodilators or other lung-related medications that might affect results.
• Avoid Heavy Meals: Do not eat a heavy meal 2 hours before the test to prevent discomfort.
• Avoid Caffeine & Alcohol: These substances can affect breathing patterns.
• Wear Comfortable Clothing: Loose-fitting clothes allow unrestricted breathing.
• Stay Relaxed: Anxiety can affect breathing, so try to remain calm before the test.

The Pulmonary Function Test Procedure

Pulmonary Function Tests involve several techniques to measure lung efficiency. Here are the most common PFTs:

1. Spirometry

What It Measures: Airflow and lung capacity

Procedure:

• You will be asked to breathe into a tube connected to a spirometer.
• The technician will ask you to take a deep breath and exhale forcefully.
• The process may be repeated to ensure accuracy.

Results Indicate:

• Obstructive lung diseases like asthma and COPD.
• Restrictive lung diseases like pulmonary fibrosis.

2. Lung Volume Measurement

What It Measures: The total amount of air in the lungs.

Procedure:

• Performed inside a sealed chamber or by inhaling a harmless gas.
• Determines how much air the lungs can hold at full capacity.

Results Indicate:

• Conditions like lung scarring and pleural effusion.

3. Diffusion Capacity Test (DLCO)

What It Measures: How well oxygen passes from the lungs into the blood.

Procedure:

• You will inhale a small amount of test gas and exhale it.
• The amount of gas absorbed by your bloodstream is measured.

Results Indicate:

• Lung damage caused by conditions like pulmonary hypertension or emphysema.

4. Bronchial Challenge Test

What It Measures: Airway sensitivity to asthma triggers.

Procedure:

• You will inhale a small dose of an irritant (e.g., methacholine) to test for airway constriction.
• Spirometry is performed before and after inhalation.

Results Indicate:

• Asthma diagnosis and severity assessment.

Understanding Your PFT Results

After the test, your doctor will review the results and explain them to you. PFT results are compared to average values based on age, gender, height, and ethnicity.

Key Parameters in PFT Results:

• FEV1 (Forced Expiratory Volume in One Second): Measures how much air you can forcefully exhale in one second.
• Normal: 80% or higher of the predicted value.
• Abnormal: Lower values may indicate obstructive diseases.
• FVC (Forced Vital Capacity): The total amount of air exhaled forcefully after a deep breath.
• Reduced FVC: Suggests restrictive lung disease.
• FEV1/FVC Ratio: The proportion of your total breath exhaled in the first second.
• Low Ratio: Indicates airflow obstruction.
• DLCO (Diffusing Capacity of the Lungs for Carbon Monoxide): Measures gas exchange efficiency.
• Low DLCO: Suggests lung damage or vascular issues.

When to See a Doctor After a PFT

If your results indicate abnormalities, you should consult your doctor to discuss further diagnostic tests or treatment plans. Seek medical attention if you experience:

• Persistent cough or shortness of breath.
• Wheezing or chest tightness.
• Difficulty performing daily activities due to breathing issues.

Conclusion

Pulmonary Function Tests are crucial for diagnosing and monitoring lung diseases. Understanding the procedure, preparation steps, and results can help you take proactive measures for better lung health. If you have concerns about your breathing, consult a specialist and undergo a PFT as needed. Early detection and proper management can make a significant difference in maintaining healthy lungs.