Pulmonary Function Tests

Last Updated December 20th, 2021

What are pulmonary function tests?

Pulmonary function tests (PFT’s) are non-invasive breathing tests employed for diagnosing and monitoring lung diseases. They are also commonly referred to as lung function tests. The most commonly performed PFT’s include spirometry, plethysmography, and diffusion studies.

Why has my physician ordered pulmonary function tests for me?

Your physician may order PFT’s for you if you have the signs or symptoms of a lung disorder. These include-

– Difficulty in breathing (dyspnea)- Dyspnea after a workout is common but dyspnea at rest can be a sign of an underlying pulmonary disorder

– Chronic chest pain– After a cardiac cause has been ruled out.

– Noisy breathing (wheezing)– An obstruction in the respiratory tract can lead to noisy breathing.

– Chronic cough– A cough lasting for more than a month is considered chronic.

– Presence of blood or mucus in the cough– These can indicate malignancy or an infection in the lungs.

– Impaired ability to exercise

– In certain cases, pulmonary function tests are carried out as a part of routine physical examination. They may also be carried out if you are about to undergo major surgery to assess your fitness for the same.

– There are industries where the employees undergo periodic PFT’s to assess the lung damage that they may have endured (e.g. coal mines).

– Your doctor may also ask you to undergo a PFT if you have a history of heavy smoking.

What do pulmonary function tests detect?

Pulmonary function tests are used to assess how well your lungs are functioning. They measure lung volumes, lung capacity, rates of flow of gases, and the efficiency of gas exchange. PFTs can aid in–

– Evaluating the effect of chronic lung diseases (asthma, COPD, cystic fibrosis) on the functioning of your lungs.

– Gauging the effect of chest trauma on your breathing effectiveness.

– Assessing if the use of bronchodilators increases the efficiency of your lungs.

– Detect early changes in pulmonary function and treat them.

– Diagnosing restrictive pulmonary disorders including scoliosis, pulmonary fibrosis, sarcoidosis, and obesity.

– Detecting a narrowing of the airways.

Are there any risks involved?

A pulmonary function test is a non-invasive, painless and relatively safe procedure. Complications arise rarely. They include-

– The procedure may precipitate an attack of asthma.
– Shortness of breath and/or bouts of coughing may occur.
– You may experience giddiness during the procedure.
– You may feel exhausted at the end of the test.
– Your physician will be monitoring your vitals during the PFT to prevent and treat complications that may arise.

What are the contraindications of undergoing a pulmonary function test?

It is not advisable to go for a PFT if-

– You have undergone an abdominal or chest surgery recently.

– You have had eye surgery in the recent past (2 weeks)- there is a risk of increasing the pressure inside the eyes during forced expiration.

– You are suffering from an active pulmonary infection including tuberculosis.

– You have been diagnosed with an aneurysm (ballooning of a major blood vessel).

– You suffer from a pneumothorax (air between your lungs and the chest wall).

– You have a history of recent myocardial infarction or unstable angina pectoris.

Is it safe for me to undergo a pulmonary function test if I am pregnant or lactating?

Yes, it is safe to undergo a PFT if you are pregnant or breastfeeding your child. Regular monitoring of pulmonary function tests may prove to be of great value in pregnant females as the presence of a lung disorder can be detected early and can be managed accordingly.

Can children undergo a pulmonary function test?

Children above the age of 5 years can undergo PFT’s.

How should I prepare for a pulmonary function test?

Spirometry, the most commonly performed PFT is carried out as an outpatient procedure. No sedation is given, and you will be conscious during the procedure. Your physician will give you the following set of instructions before you embark on this test-

– Do not smoke at least 1 hour before the test.

– Do not consume alcohol for at least 4 hours before the test.

– Abstain from exercising heavily for at least 30 minutes before the test.

– Wear loose-fitting, comfortable clothes. Tight-fitting clothes can make it difficult for you to breathe; this may tamper with the results.

– Do not eat a large meal within 2 hours before the test.

– If you are already taking a bronchodilator (oral/inhaled), your physician may ask you not to take it on the day of the test.

Do I need to fast before the test?

There is no need to fast before undergoing a PFT. However, you will be instructed to consume a light meal before proceeding to the hospital for this test.

How is a pulmonary function test performed?

Spirometry is a simple, non-invasive, safe and easy to conduct test. The procedure followed is –

-You will be asked to empty your bladder and bowel before proceeding for the test.

– If you wear artificial dentures, you will be instructed to continue wearing them.

– You will be escorted to the place assigned for carrying out the test.

– Your physician will explain the steps involved in the procedure to you.

– You will be asked to sit in a comfortable chair.

– A soft nose clip will be placed on your nose. This will ensure that you breathe through your mouth only.

– A sterile mouthpiece will be given to you. You will be asked to make a seal over the mouthpiece with your mouth.

– The mouthpiece is attached to a spirometer, an apparatus that measures the amount of air you inhale and exhale.

– You will be instructed to inhale and exhale air in various manners.

– The spirometer will record the volume of air during each cycle.

– Your physician may ask you to take a bronchodilator and repeat the procedure to see the effects of the medicine on your lungs.

If you are on supplemental oxygen, the same may not be provided during this test. However, the physician will keep a constant vigil on your parameters to look for any sign of dizziness and syncope.

Body plethysmography (also known as lung volume measurement)– The procedure is like that of spirometry but in this procedure, you will be placed inside a see-through glass box resembling a telephone booth. You need to talk to your physician if you suffer from claustrophobia (a fear of closed spaces).

Diffusion tests-In this procedure, you are made to inhale air containing a small, safe amount of carbon monoxide. After holding your breath for 10 seconds, you will be asked to exhale. This exhaled sample is then analyzed,

What do the results of my PFT convey?

Spirometry yields multiple lung measurements, the most important being-

Forced vital capacity (FVC)– The maximum amount of air that you can exhale after taking your biggest breath in.

Forced expiratory volume (FEV1)– The maximum amount of air that you can exhale during the first second of the spirometry test.

FEV1/FVC ratio is another important yardstick to determine the functioning of the lungs.

It is to be noted that there are no standard values for lung capacities. Your findings will be compared to the average for someone belonging to the same age, height, sex, and race.

How to interpret the results?

Spirometry result NormalAbnormal
FVC & FEV1Equal to or greater than 80%
Mild- 70-79%
Severe- Less than 60%
FEV1/FVCEqual to or greater than 70%
Mild- 60-69%
Moderate- 50-59%
Severe- Less than 50%

What do these results indicate?

Restrictive lung diseases– In these pulmonary disorders, the FVC tends to be abnormal. This implies that the lung is restricted from filling to its normal capacity of air. Asbestosis, scoliosis, and sarcoidosis are a few diseases with restrictive lung pathology.
Obstructive lung diseases– The airflow in the lungs is hampered in these disorders, therefore FEV1 and FEV1/FVC are abnormal. Asthma, emphysema, and chronic bronchitis are some of the obstructive lung diseases.

How long does a pulmonary function test last?

A spirometry test lasts about 15 to 30 minutes.

What is the cost of undergoing a pulmonary function test in India?

The cost of undergoing a spirometry test in India is INR 500-1500 depending on the city you reside in.

How common is bronchitis in India?

COPD manifests in the form of emphysema and bronchitis. COPD is one of the badly neglected chronic lung diseases in India. It is the second most common cause of death in India, resulting in over 958,000 deaths in the year 2017.

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