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What Is A Pulmonary Function Test And What To Expect?

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Dayton Respiratory Center

Feb 06 2022

5 mins read

Do you remember being awfully upset when you were asked to visit a dentist as a kid? 

Research says there are many reasons for this, including a fear of “being taken over by another” and an invasion of your interpersonal space.

Unfortunately, certain medical procedures cannot totally avoid this. Some methods such as bronchoscopies and endoscopies involve internal exploration to investigate your medical issue. 

However, you will be pleased to know that not all medical tests require an intrusion of your personal space, a feeling of loss of control, the use of sharp instruments, anesthesia or needles. 

A pulmonary function test or a PFT is a non-invasive, externally performed medical procedure. It is executed by the patient mostly, with the help of instructions from the medical staff.

The test is done for doctors to understand and evaluate how well your lungs function.

What exactly does the PFT measure?

PFTs can be performed using two methods - Spirometry and Plethysmography.

The pulmonary function test measures vital components that aid your doctor to make the right diagnosis and eventually provide optimum treatment. It is always better to be an informed patient, and be aware of what parameters the PFT measures. 

The PFT provides:

The tidal volume: The volume of air that you inhale or exhale during regular breathing

The minute volume: The volume of air that you exhale in one minute

The vital capacity: The volume of air that you can exhale after complete inhalation

Functional residual capacity: This is the residual air remaining in your lungs after a normal exhalation

Residual volume: It is the residual air in the lungs after you exhale to your maximum 

Total lung capacity: It is the total amount of air in your lungs when it is filled with maximum volume of air

Forced vital capacity: This is the amount of air that you exhale forcefully as well as quickly, after you inhale to your maximum capacity

Forced expiratory volume: This is the amount of air you expire for the first three seconds of the forced vital capacity taking into consideration each second separately

Forced expiratory flow: It is the average flow rate measured during the middle half portion of the forced vital capacity 

Peak expiratory flow rate: It is the quickest rate at which you can force air out from your lungs

It is important to note that every person’s normal values for the Pulmonary function test varies. Your results will be compared to the average person’s results of the same age, sex, race, and height. 

These results are also often compared to previous PFT test results to note improvements or downfalls of the lung functioning.

Why does your doctor ask for a pulmonary function test?

There are a variety of reasons your doctor might ask you to get this test done. A pulmonary function test may also be done in healthy people as a part of a routine testing. 

You doctor may also require it to help them to diagnose health issues such as:

  • Allergies
  • Respiratory infections
  • Difficulty breathing due to chest injuries
  • Chronic lung diseases or conditions ( eg: emphysema, chronic bronchitis, asthma, bronchiectasis)
  • Asbestosis 
  • Restrictive airway problems 
  • Sarcoidosis
  • Scleroderma 

What can you expect?

Prior knowledge of what you can expect and experience can calm people down for the actual event or procedure. 

Spirometry: The spirometer is a device that looks like a mouthpiece. It is connected to an electronic machine. 

Plethysmography: You are asked to sit or stand up in an air-tight box and perform the tests. 

The medical staff or your healthcare provider will explain the procedure and instruct you on what you have to do. You may be asked to sign your consent on form. Remember to ask any questions that you may have and mention the medicines you are taking. 

The following are pointers of what you can expect at the procedure:

  • The pulmonary function test is usually an outpatient procedure which means you can return home the same day. 
  • You might be asked to loosen your clothing before the procedure. 
  • If you use dentures, you will be asked to wear them during the procedure.
  • You will be asked to use the washroom to empty your bladder prior to the test.
  • You will be asked to be seated on a chair and a soft clip will be used to clip your nose so that you can breathe through your mouth. 
  • A disinfected mouthpiece will be given to you, over which your mouth should form a tight seal. You will then be instructed to breathe in different ways. 
  • You will be watched over for any side effects such as dizziness, trouble breathing, coughing or an asthma attack. Please visit your pulmonologist if these symptoms linger. 
  • Sometimes, you may be given a bronchodilator and asked to repeat certain tests for review. 

If you are someone who has a known history of breathing problems, you might feel tired after the pulmonary function test. You will be allowed to rest after the test and your healthcare provider will discuss the results with you after evaluation. 

A pulmonary function test is one of the best methods to evaluate and diagnose lung and breathing problems without sedation, anaesthesia, or using intrusive procedures. It requires the cooperation and willingness of the patient, without which it will not yield the right results.

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