Comprehensive Guide to Pulmonary Function Test

Comprehensive Guide to Pulmonary Function Tests

Pulmonary function tests (PFTs), also known as lung function tests, are essential tools in assessing lung health. This guide provides an overview of what PFTs are, why they are important, and when they are recommended. PFTs help diagnose, monitor, and manage respiratory conditions, offering valuable insight into lung function and overall respiratory health.

PFTs include a variety of tests that measure different aspects of lung function, such as lung volume, capacity, flow rates, and gas exchange. Common tests include spirometry, lung volume measurement, diffusion capacity tests, and peak flow monitoring.

What Are Pulmonary Function Tests?

PFTs are a series of non-invasive tests that evaluate how well your lungs are working. They measure the amount of air you can inhale and exhale, how efficiently your lungs transfer oxygen into the blood, and the overall airflow through your respiratory system.

PFTs are crucial in diagnosing and monitoring chronic lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). They allow healthcare providers to detect lung issues early, monitor disease progression, and assess the effectiveness of treatments.

Why Are They Important?

• Diagnosis and Management:
  PFTs help identify the presence of respiratory conditions and provide a baseline for treatment plans.

• Severity Assessment:
  They measure the extent of lung impairment and track changes over time.

• Pre-Surgical Assessment:
  PFTs are often used to evaluate lung function before surgeries, ensuring patients are at lower risk for complications.

• Treatment Monitoring:
  Regular testing helps doctors assess how well medications or therapies are working and adjust treatment plans accordingly.

When Are They Needed?

• Common Indications:
  Unexplained shortness of breath, chronic cough, wheezing, or a history of asthma or COPD.

• Occupational Hazards:
  Exposure to dust, chemicals, or smoke that may impact lung health.

• Specific Conditions:
  Asthma, COPD, interstitial lung disease, and other chronic respiratory disorders.

• Monitoring Disease Progression:
  Repeat testing is often necessary to track how a condition evolves or to evaluate treatment effectiveness.

What Are The Different Types of PFTs?

PFTs come in several forms, each measuring a different aspect of breathing. The choice of test depends on your symptoms, medical history, and what your healthcare provider needs to assess. These tests help confirm a diagnosis, monitor an existing condition, or guide treatment decisions.

Spirometry

Spirometry is one of the most common lung function tests. It measures:

• How much air you can breathe in and out (lung volume)

• How fast you can blow air out (flow rate)

Spirometry is widely used to diagnose and monitor conditions such as asthma and COPD. During the test, you'll be asked to take a deep breath and exhale forcefully into a mouthpiece connected to a machine called a spirometer. Clear instructions and proper technique are important to ensure accurate results.

Peak Flow Measurement

Peak flow measurement evaluates how quickly you can blow air out of your lungs. It is especially useful for people with asthma.

This test helps to:

• Monitor daily lung function

• Detect early signs of asthma flare-ups

• Identify triggers that may worsen symptoms

Peak flow meters are small, portable devices that can be used at home, making them ideal for self-management plans.

Body Plethysmography

Body plethysmography measures total lung volume, including the amount of air left in your lungs after you exhale. This information helps diagnose restrictive lung diseases, where the lungs cannot fully expand.

During the test, you sit in a sealed, transparent chamber and breathe through a mouthpiece. Pressure changes inside the chamber help calculate your lung volumes. The test is non-invasive and provides highly accurate results.

Lung Diffusion Capacity

Lung diffusion capacity tests, also known as DCLO, assess how well your lungs transfer gases like oxygen from the air into your bloodstream. 

You will be asked to inhale a harmless gas mixture and hold your breath briefly before exhaling. The machine then measures how much gas was absorbed, providing insight into how well your lungs are functioning.

This test is particularly helpful in evaluating conditions such as pulmonary fibrosis, emphysema, or other disorders affecting the lung tissue.

Cardiopulmonary Exercise Testing

Cardiopulmonary exercise tests evaluate your ability to tolerate physical activity (fitness). These tests often involve walking on a treadmill or cycling on a stationary bike while your breathing, heart rate, and oxygen levels are monitored. Cardiopulmonary exercise testing is mainly used in determining fitness for surgery or in athletes for fitness monitoring.

Bronchial Provocation Testing

Bronchial provocation testing helps confirm asthma when symptoms are present but routine tests appear normal. During the test, you inhale a substance such as methacholine, which can trigger mild airway narrowing.

Your breathing is then measured using spirometry to assess how your airways respond. This test is typically performed under close supervision and is highly valuable in diagnosing asthma.

FeNO Measurement

FeNO (fractionally exhaled nitric oxide) measurement assesses the level of nitric oxide in your breath, which reflects airway inflammation. It is especially useful in diagnosing and monitoring asthma, particularly when symptoms or spirometry results are unclear.

The test is simple and non-invasive. You will be asked to exhale steadily into a handheld device that measures nitric oxide levels. Higher levels may indicate airway inflammation and help guide treatment decisions, such as adjusting inhaled corticosteroids.

Six-Minute Walk Test (6MWT)

The six-minute walk test evaluates functional exercise capacity by measuring the distance you can walk on a flat surface within six minutes. It helps assess how lung disease affects everyday activities and can be used to guide prognosis.

The test is conducted in a quiet hallway or designated testing area. You will be instructed to walk at your own pace for six minutes while your breathing, heart rate, and symptoms are monitored. The results help your healthcare provider determine disease severity and monitor treatment outcomes.

How Should You Prepare for the Test?

To ensure accurate results, follow these preparation guidelines, unless instructed otherwise:

• Avoid heavy meals for at least 2–3 hours before testing.

• Refrain from smoking for at least one hour prior to the test.

• Avoid vigorous exercise before the test.

• Wear comfortable clothing that won’t restrict breathing.

• Wear your dentures (if applicable).

• Follow instructions regarding medication use. Some inhalers may need to be withheld before testing, while others should be continued. Your healthcare provider will give specific guidance.

What to Expect During the Test?

PFTs are typically performed in a clinic or respiratory laboratory by trained professionals. You’ll be guided through each step to ensure you understand the process.

During the test:

• You will be asked to breathe into different devices that measure lung performance.

• Clear instructions will be provided, and your cooperation is essential for accurate results.

• Some tests may require deep breaths, rapid exhalation, or brief breath-holding.

You may experience minor sensations such as light-headedness or shortness of breath, but these usually pass quickly. Healthcare staff will monitor you throughout to ensure your comfort and safety.

Are There Any Risks Involved?

PFTs are generally very safe and well‑tolerated. Most people experience no issues, and the tests are supervised by trained healthcare professionals.

Possible, but mild, side effects may include:

• Temporary shortness of breath

• Light-headedness after deep or forceful breathing

• Mild coughing

These symptoms usually pass quickly. Caution may be needed if you’ve had recent eye, chest, or abdominal surgery, or if you have unstable heart conditions. Your healthcare provider will assess your suitability before testing.

How to Interpret the Results?

After your test, your GP or respiratory specialist will review the results with you. Key measurements include:

• FEV1 (Forced Expiratory Volume in 1 second): How much air you can forcefully exhale in one second. Low values may indicate airway obstruction.

• FVC (Forced Vital Capacity): The total amount of air you can exhale after a deep breath. Reduced values may suggest restrictive lung disease.

• DLCO (Diffusing Capacity): How well your lungs transfer oxygen into your blood. Low levels may point to conditions like pulmonary fibrosis or emphysema.

These results help diagnose lung conditions, determine disease severity, and guide treatment plans.

What Conditions Can Be Diagnosed?

Pulmonary function tests assist in diagnosing several conditions, including:

• Asthma

• Chronic Obstructive Pulmonary Disease (COPD)

• Pulmonary fibrosis and other interstitial lung diseases

• Occupational lung diseases

Different tests contribute unique information, for example, spirometry helps identify asthma or COPD, while diffusion tests are key in diagnosing lung tissue disorders. PFTs can also help rule out other causes of symptoms such as cardiac issues.

See a GP today about a lung function test

If you’re experiencing breathing difficulties or have concerns about your lung health, book an appointment with a GP at Myhealth. Our experienced doctors can assess your symptoms, determine whether pulmonary function testing is needed, and guide you through the next steps.

Myhealth clinics offer:

• Modern facilities and reliable testing options

• Access to experienced, patient‑centred healthcare providers

• Personalised care and clear explanations of your results

Take charge of your lung health, visit the Myhealth website or contact your nearest clinic to schedule a consultation.