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Pulmonary Function Tests - Indications, Uses, and Types

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Pulmonary Function Tests - Indications, Uses, and Types

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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.

Written by

Dr. Saberitha

Medically reviewed by

Dr. Kaushal Bhavsar

Published At July 12, 2022
Reviewed AtOctober 14, 2022


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.

Frequently Asked Questions


What Examinations Comprise a Pulmonary Function Test (PFT)?

Lung function tests, sometimes referred to as pulmonary function tests or PFTs, are a series of examinations that determine how well the lungs are functioning. 
They consist of: 
- Spirometry: The most popular test for lung function. 
- Lung Volume Test: It is also referred to as body plethysmography. 
- Exercise Stress Test: helps in assessing the heart's reaction to physical exertion, which aids in the diagnosis of heart conditions.
- Gas Diffusion Test: It measures the passage of gasses across the alveolar-capillary membrane of the lung and evaluates lung function.


What Pulmonary Function Test Is Most Often Performed?

Spirometry is the most popular pulmonary function test. It is helpful for identifying chronic respiratory conditions, including emphysema and asthma (chronic obstructive pulmonary disorder). Spirometry can calculate how much air was expelled from the lungs during an expiration. It calculates the speed at which the lungs exhale.


What Is a Pulmonary Function Test, and How Is It Performed?

PFTs (pulmonary function tests) are noninvasive examinations that demonstrate how effectively the lungs are functioning. The examinations gauge lung size, function, flow rates, and gas exchange. The healthcare professional may use this information to diagnose and treat some lung conditions.


Can PFT (Pulmonary Function Test) Scan for Lung Injury?

PFTs may be used to evaluate lung function in individuals with heart or lung issues, smokers, or other medical disorders prior to surgery or other operations. PFTs are also used to evaluate the effectiveness of treatment for chronic lung conditions like emphysema and asthma.


What Is a Typical PFT Reading?

An FEV1/FVC (forced expiratory volume/ forced vital capacity) ratio of more than 0.70 with both FEV1 and FVC above 80 percent of the expected value is considered normal spirometry data. TLC (total lung capacity) exceeding 80 percent of the predictive value when lung volumes are performed is considered normal. A diffusion capacity that is greater than 75 percent of the projected value is regarded as typical.


How Much Time Does a PFT Test Need?

Spirometry testing requires not more than 30 minutes, and PFT usually takes one hour to finish. The pulmonologist, who has received specialized training in pulmonary (lung) disorders and conditions, interprets the PFTs.


How Old Should the Lungs Be?

By the time individuals are 20 to 25 years old, their lungs are fully developed. It is typical for lung function to gradually diminish with aging after the age of 35. As one age, this may make breathing a little more challenging.


What Does a Poor PFT Result Mean?

Results that are abnormal typically indicate that one may have lung or chest disease. Emphysema, asthma, chronic bronchitis, and other lung conditions can cause the lungs to hold too much air and take longer to empty. Obstructive lung disorders are the name given to certain lung conditions.


How Can One's Pulmonary Function Be Improved?

The lungs can benefit from both aerobic exercises and muscle-strengthening exercises. Exercise the heart and lungs with aerobic exercises like walking, running, or jumping rope to ensure they are working properly.


Is a Normal PFT a Sign of Asthma?

Asthma is a variable condition with intermittent symptoms, so a normal Pulmonary Function Test (PFT) result does not necessarily mean that a patient has asthma. Airway inflammation and hyperreactivity, which characterize asthma, may not always be found during PFTs, especially if the test is carried out when the subject is asymptomatic. Regardless of the results of the PFT, the diagnosis of asthma requires a thorough evaluation that includes the patient's medical history, clinical symptoms, and possibly other specialized tests. A normal PFT does not prove or disprove asthma on its own.


What Foods Are Beneficial for Lungs?

Coffee, fatty salmon, peppers, tomatoes, olive oil, oysters, blueberries, pumpkin, and dark leafy greens are a few examples of foods and drinks that have been shown to enhance lung function. To advance the well-being of the lungs, try to include a couple of the foods and drinks mentioned above in the diet.


How Much Lung Capacity Is Enough?

The total volume of air in the lungs at maximum inspiratory effort is known as lung capacity (sometimes known as total lung capacity or TLC). The typical lung volume in healthy persons is around 1.58 US gallons (six liters).


Can a PFT Detect Heart Issues?

The proactive cardiologist can find a solution through spirometry and PFT testing. Spirometry plays a critical role in determining cardiovascular risk, especially coronary artery disease, despite the common misconception that it is a lung-health-specific diagnostic tool.


Is Pneumonia Detected By PFT?

PFT is a helpful tool for identifying and managing high-risk pediatric pneumonia patients who may require more frequent monitoring and follow-up after being released from the hospital, as well as a referral to a pulmonologist and additional PFT.


Can One Check Their Lungs at Home?

A home spirometer or a peak flow meter is used in a home lung function test to track and assess any daily breathing issues one might experience. The peak expiratory flow can be measured with a peak flow meter. One can measure their forced expiratory volume at 1 second with a home spirometer (FEV1).


Is Water Consumption Permitted Before the Pulmonary Function Test?

Before the test, individuals can eat and drink, but doctors generally do not advise doing any strenuous exercise or eating a substantial meal right before the visit. The doctor can urge the patient to adhere to additional recommendations before testing, such as medicines, depending on the patient's medical condition.


How Difficult Is a PFT Exam?

It takes roughly 15 minutes and is painless. One can sit in a transparent plastic box for plethysmography. They use a customized mouthpiece and a nasal clip to breathe through the mouth. An examination of the lung's ability to diffuse oxygen into the blood is known as lung diffusion capacity.
Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


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