News & Notices

Pulmonary Function Test- By: Dr Nabin Prakash Shah


By: Dr Nabin Prakash Shah


Pulmonary Function test


Pulmonary function tests (PFT’s) are breathing tests to find out how well you move air in and out of your lungs and how well oxygen enters your body.

There are 2 types of disorders that cause problems with air moving in and out of the lungs:

  • Obstructive. This is when air has trouble flowing out of the lungs due to airway resistance. This causes a decreased flow of air.
  • Restrictive. This is when the lung tissue and/or chest muscles can’t expand enough. This creates problems with air flow, mostly due to lower lung volumes.


Lung function are important investigations which:

• Help diagnose suspected lung disease;

• Help in planning treatments and decide whether treatments should be continued, changed, or are no longer needed.



Lung function tests can be used to:

■ Compare your lung function with known standards that show how well your lungs should be working.

■ Measure the effect of chronic diseases like asthma, chronic obstructive lung disease (COPD), or cystic fibrosis on lung function.

■ Identify early changes in lung function that might show a need for a change in treatment.

 ■ Detect narrowing in the airways.

■ Decide if a medicine (such as a bronchodilator) could be helpful to use.

■ Show whether exposure to substances in your home or workplace have harmed your lungs.

 ■ Determine your ability to tolerate surgery and medical procedures.


Indications for Measuring Pulmonary Function

  • Common indications for pulmonary function testing (PFT) in older adults are symptoms that suggest lung disease, such as dyspnea, chest tightness, cough, and wheezing.
  • However, some older patients may not experience these symptoms even in the presence of lung disease because they will instinctively limit their activities to avoid exertion that might cause the symptoms to occur.
  • Thus, their low activity levels may preclude symptoms, even in the presence of significant (but undiagnosed) pulmonary disease.
  • There is also evidence to suggest that older individuals have a diminished perception of bronchospasm compared with younger adults. With these concerns in mind, it is reasonable to have a lower threshold for obtaining PFTs in older adults.


What are the risks of pulmonary function tests?

Because pulmonary function testing is not an invasive procedure, it is safe and quick for most people. But the person must be able to follow clear, simple directions.

All procedures have some risks. The risks of this procedure may include:

  • Dizziness during the tests
  • Feeling short of breath
  • Coughing
  • Asthma attack brought on by deep inhalation

In some cases, a person shouldn’t have PFTs. Reasons for this can include:

  • Recent eye surgery, because of increased pressure inside the eyes during the procedure
  • Recent belly or chest surgery
  • Chest pain, recent heart attack, or an unstable heart condition
  • A bulging blood vessel (aneurysm) in the chest, belly, or brain



To Prepare

  • Do not smoke for 4 to 6 hours before the test.

 • Only eat a small meal before the test so you can take deep breaths during the test.

 • If you take lung medicine, your doctor will tell you which medicines you need to stop taking and for how long before the test.


Results of the test:

Your performance on these tests will be compared with what is predicted for you, based on your gender, age, height and race.

• Forced Vital Capacity (FVC)is the amount of air you could force from your lungs during a single breath. Normal FVC is about 80 – 100% of predicted. A decrease in the FVC may indicate lung disease.

 Repeated exposure to certain irritants in your work without taking proper work precautions such as wearing a respirator mask can cause your lungs to scar and become stiff. This stiffness makes it hard to take a deep breath in.


Forced Expiratory Volume over One Second (FEV1)is the amount of air that you could force from your lungs in the first second of your single breath. Normal FEV1 is about 80 – 100% of predicted.


 • Forced Expiratory Volume over One Second / Forced Vital Capacity Ratio (FEV1/FVC)is the percent of your single breath that you could breathe out during the first second. Normal FEV1/FVC is above 75%, although this value changes with age. A decrease in the FEV1/FVC ratio indicates obstructive lung disease.

Exposure to certain irritants or allergens can cause the muscle surrounding the airway to spasm and cause narrowing of the bronchi or airways. This narrowing makes it hard to breathe air in and out. This could be compared to trying to breathe out quickly through a small straw. Examples of obstructive lung disease are reactive airway disease, asthma, bronchitis and emphysema.

 • Peak Flow (PF or PEF)is a measurement of the fastest flow that you could breathe out. Normal Peak Flow is usually greater than 80% of predicted.

 • Forced Expiratory Mid-Flow (FEF 25-75%)is your single breath divided into 4 parts, This number reflects how fast the air was coming out of your lungs during the middle 2 parts, between 25% and 75% of your breath. Normal FEF 25-75%, is greater than 80% predicted.