Respiratory health Data Verified

Pulmonary Function Tests - Indications, Uses, and Types

Published on Jul 12, 2022 and last reviewed on Oct 14, 2022   -  5 min read


A pulmonary function test is also called a lung function test. Read the article below to know more about the types and uses of pulmonary function tests.

Pulmonary Function Tests - Indications, Uses, and Types


The pulmonary function test helps assess the working capacity of the lungs by measuring the amount of airflow from it. Read the below article to know more.

What Are the Indications for Pulmonary Function Tests?

Following are the indications for performing pulmonary function tests;

  • A pulmonary function test is used to assess the working capacity of the lungs before doing any major surgery.
  • This test is used to diagnose chronic medical conditions like chronic obstructive pulmonary disorder (COPD).
  • Long-term diseases like asthma and breathing difficulty are analyzed to check the severity of the disease.
  • Any lung disease can be interpreted using a pulmonary function test.

How Useful is the Pulmonary Function Test During Diagnosis?

  • Lung Capacity: A pulmonary function test is used to determine the capacity of the lungs to supply oxygen to all body parts.

  • Emphysema: The doctors use pulmonary function tests to evaluate the improvement in chronic conditions like bronchitis and chronic obstructive pulmonary disorder like emphysema.

  • Respiratory Illness: This test is useful to track the record of any respiratory infections.

  • Asthma: A pulmonary function test is used to monitor conditions like asthma.

  • Pulmonary Fibrosis: It is used to diagnose pulmonary fibrosis, in which the lung lacks the functioning capacity.

  • Bronchiectasis: In bronchiectasis, the airways are blocked by infections. A pulmonary function test is used to evaluate the bronchus (main air passage to the lungs).

  • Asbestosis: Life-threatening diseases like asbestosis are diagnosed by pulmonary function tests. Asbestosis results in breathing difficulty. A pulmonary function test is used to observe the airflow.

  • Respiratory Muscles: Chronic respiratory conditions weaken the chest muscles. A pulmonary function test is used to inspect the respiratory muscles of the chest wall.

  • Sarcoidosis: Organ inflammatory conditions like sarcoidosis affect the lungs functioning ability. It can be diagnosed using pulmonary function tests.

  • Surgery: Pulmonary function tests play a vital role in lung cancer. It is used to determine whether the surgery is required or not.

What Is the Purpose of Different Types of Pulmonary Function Tests?

There are more than five types of pulmonary function tests. The doctor might ask to take one or more tests depending upon the type of respiratory illness.

1. Spirometry:

It is useful for diagnosing chronic respiratory ailments like asthma and emphysema (chronic obstructive pulmonary disorder). Spirometry can estimate the quantity of air that expired out of the lungs. It estimates how promptly the lungs exhale.

Steps to Follow for Spirometry Test:

  • The machine is attached to a mouthpiece made out of plastic. The patient is made to sit straight to allow an easier airflow from and to the lungs. The mouthpiece should fit the mouth tightly so that the air flows through the mouthpiece to the machine.
  • The nose clip is worn to prevent breathing through the nose. The patient must take a deep breath before exhalation and blow out the air completely from the lungs during exhalation.
  • The same technique is repeated during the test two more times. Normal breathing is permitted in between the two tests.
  • The doctor prescribes medication to ease the airflow. In addition, spirometry can examine the exhalation capacity of the lungs after the therapy.

2. Cardiopulmonary Exercise Test (CPET):

A cardiopulmonary test is used to assess the functioning ability of the lungs after a workout. During physical activity, our body consumes oxygen as an energy source. CPET can measure the amount of oxygen utilized by the body. The treadmill is the most commonly used by the doctor to determine physical exertion. CPET is used to inspect various organs like the heart, lungs, muscles, and blood vessels.

It has various parts like EKG (electrocardiogram) leads, a cuff, a pulse oximeter, and a mouthpiece. The EKG leads are used to evaluate the heart rate. The oximeter is used to measure blood oxygen level saturation. A meter is attached along the tube and mouthpiece. This meter estimates the airflow in and out of the lungs. The time taken for this test is around 10 to 12 minutes.

3. Bronchial Provocation Test:

The bronchial provocation test is used to evaluate the effectiveness of the lungs during asthma. The doctor exposes you to the allergy to check the responsiveness of the lungs.

This test also examines lung capacity after physical exertion. Methacholine causes constriction of the airways. The asthma patient is more prone to methacholine reactions. This test evaluates the symptoms of asthma due to methacholine.

4. Exhaled Nitric Oxide Test:

As the name says, this test measures the amount of nitric oxide exhaled in the breath. You should take a deep breath and exhale entirely into the mouthpiece. The monitor shows the percentage of nitric oxide present in the breath.

  • Interpretation - High level of nitric oxide indicates the presence of asthma.

  • Treatment - Corticosteroid therapy is commonly used for treating asthma.

5. Pulse Oximetry Test:

This test estimates the oxygen saturation level in the blood. The pulse oximeter is positioned in the forehead, finger, or other body parts. Results are obtained at the exact moment.

  • Interpretation - If the saturation level is below 95 %, it indicates the sign of any respiratory diseases like asthma and chronic conditions like pneumonia and COPD (chronic obstructive pulmonary disorder).

6. Plethysmography Test:

A mouthpiece is attached to the booth to calculate the air pressure. The lung volume is measured using this test when you exhale through the mouthpiece.

7. Diffusion Capacity Test:

The diffusion capacity test analyzes the functional capacity of the alveoli in the lungs. You should inhale carbon monoxide before the test. The diffusion capacity test determines the capacity of the lungs to transport oxygen and carbon dioxide.

How Should You Prepare for the Pulmonary Function Test?

Before taking the test, you must stop the medications. Medications interfere with the test results. So, you should stop the medication taken for asthma and chronic obstructive pulmonary disorder. You should not eat stomach full or drink products that contain caffeine. You should not smoke or drink alcohol before the test.


Before taking the pulmonary function test, prepare for the test as per the doctor’s advice.

You can take a rest after doing physical exertions during the cardio-pulmonary exercise test. However, you should avoid this test if you have undergone heart surgery or eye surgery in recent months. It is considered a safe test because the test involves only breathing action.

A pulmonary function test is used as an adjunct to the final diagnosis. Since the test involves faster breathing, there is a feeling of light-headedness after the test. Fainting is the most common experience after a pulmonary function test. In severe asthma cases, the test may worsen the condition. However, medical professionals will help the patient to overcome such situations.

Last reviewed at:
14 Oct 2022  -  5 min read




Comprehensive Medical Second Opinion.Submit your Case

Related Questions & Answers

Inspite of medications, I am not relieved from chest tightness. Is it COPD?

Query: Hi doctor, I am a 50-year-old female, with a history of childhood asthma, that was virtually a nonissue in my adult life until three weeks ago. I had a recent SVF adipose stem cell treatment for OA with a cold on board. I felt tight chested then but not bad enough to take my Ventolin. A few days l...  Read Full »

Why do I have cough periodically?

Query: Hello doctor, I am an electrical engineering student. My age is 21 years. I have been facing some problems in the last five years. When I get a cough, I feel uneasy, and this problem is there throughout the year. If I do not take any medicine, water comes out of my nose and irritates me. I consulte...  Read Full »

Lifestyle Changes to Manage Advanced COPD

Article Overview: Advanced COPD is the severe stage of lung disease, where the symptoms get worsened and affect daily activities. Let us discuss the measures to be taken to manage it. Read Article

Kaushal Bhavsar
Kaushal Bhavsar
Pulmonology (Asthma Doctors)

Introduction: Progressive chronic obstructive pulmonary disorder (COPD) is a severe lung disease, and the patient does not respond well to treatment. Studies show that this develops in patients above 40 years. Specific modifications in the lifestyle during the end stage of COPD can help improve the ...  Read Article

Popular Articles Most Popular Articles

Do you have a question on Pulmonary Function Tests or Copd?

Ask a Doctor Online

* guaranteed answer within 4 hours.

Disclaimer: No content published on this website is intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek advice from your physician or other qualified healthcare providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website. Read our Editorial Process to know how we create content for health articles and queries.