PFT tests help doctors to screen for certain lung diseases and to check the general health of your lungs. These tests help doctors to measure the progression of certain diseases, and they can also help the doctor to evaluate the effectiveness of the therapies and medications prescribed.

Sometimes, doctors want the tests done so they have a good baseline of the function of their patient’s lungs, so that going forward, they can monitor their patient closely for any lung function changes. In other cases, the PFT is used to eliminate diagnosis of certain diseases.

What is a PFT?

Frequently Asked Questions

What is a PFT?

A Pulmonary Function Test or PFT is a group of tests performed to assess the condition of your lungs in order to screen for the presence of lung disease, monitor changes in severity, or response to treatment. You will be seated, with nose plugs on, for the test. While you breathe through a mouthpiece, the technologist will guide you through a series of breathing exercises. As the breathing exercises require some effort to perform, the technologist will ask you some pre-test questions to screen for possible contraindications. Click the button below to review the Patient Instructions.

How do I get a PFT?

If you are feeling breathless, you should be assessed by a doctor.
We can help to investigate your shortness of breath, but you must get a referral from your doctor to have the PFT done here at Credit Valley Pulmonary Diagnostics.

The cost is covered by OHIP.

Why has my doctor referred me for this test?

Common reasons to be referred for a PFT include chronic cough, asthma, COPD, shortness of breath, abnormal chest x-ray findings, or to assess fitness for certain surgeries.

These tests help doctors to measure the progression of diseases, and they can also help to evaluate the effectiveness of therapies.

A complete PFT consists of
the following 5 tests:

A complete PFT consists of
the following 5 tests:

Oxygen Saturation by Pulse Oximetry
Pulse Oximetry uses a fingertip sensor to non-invasively estimate and monitor the level of oxygen in the blood, as well as your heart rate. For all healthy individuals the oxygen level in the blood will be between 93% and 100%. A low blood oxygen level typically represents significant lung disease or acute illness.
Spirometry (baseline only, or pre and post bronchodilator)

Spirometry is the most commonly used breathing test to screen for and monitor lung disease. Spirometry measures the maximum amount of air you can exhale, using maximum effort (Forced Vital Capacity, or FVC), how much of the FVC empties in the 1st second of exhalation (Forced Expiratory Volume in 1 Second, or FEV1), as well as Peak Flow and other rates of airflow throughout exhalation. These values (and their relation to one another) are critical measures of lung function as they show the size of your lungs and how easily the air moves through your lungs as you breathe. Abnormally small capacity can represent restrictive or severe obstructive lung disease. Abnormally slow airflow is a definitive measure of obstructive lung disease such as asthma or emphysema/COPD. Spirometry is usually done at two separate points during a PFT, first as a baseline test, and then again after taking a bronchodilator (inhaler) in order assess for asthma (reversible airflow obstruction). Because you need to use maximum effort for good quality spirometry, doing the test may make you cough, feel lightheaded or dizzy, or even cause muscle spasms/cramping. Bronchodilators such as salbutamol can have side effects – light headedness, mild tremor, restlessness, and palpitations. The technologist will coach you through the test to minimize any possible discomfort.

Lung Volumes (measured using Body Plethysmography)

Body Plethysmography measures the total capacity of the lungs as well as the breakdown of normal breathing and reserve volumes in the lungs by using an enclosed glass booth to measure pressure and volume changes during your breathing. This test is used to screen for small lung volumes associated with restrictive lung disease (such as Pulmonary Fibrosis), and overly large lung volumes associated with significant obstructive lung disease (such as emphysema or COPD).

Airways Resistance
Airways Resistance measures the resistance of the airflow through predominantly the large airways. This test can be done on its own but is often done as part of Lung Volumes testing. Abnormally high Airways Resistance is associated with obstructive lung disease.
Carbon Monoxide Diffusion Capacity (DLCO)
DLCO measures how fast a trace amount of carbon monoxide is absorbed through the lung tissue into the bloodstream. Because oxygen and carbon dioxide diffuse through the lung tissue during normal breathing this test represents how efficiently this gas exchange occurs. Diffusion Capacity can be abnormally low due to chronic obstructive lung disease and restrictive lung disease, as well as pulmonary vascular disease.
What could be wrong with me?
Why am I having trouble catching my breath?

Although there are many reasons that a patient may be having difficulty breathing, some of the most common causes are:


A constriction of the airways. Most commonly diagnosed when a patient complains of “wheezing” and a general feeling of shortness of breath when exposed to certain environments or after exercise.

Idiopathic Pulmonary Fibrosis

This occurs when the lung tissue becomes scarred, and thicker than normal. This causes your lungs not to work properly and can lead to shortness of breath.

Other Interstitial Lung Diseases

It is essentially an umbrella term for a large group of lung diseases which cause scarring of the lung tissue, making it difficult for patients to breathe normally. Some causes include occupational exposures, certain medications, or autoimmune diseases.

Deconditioning or Poor Fitness

Some patients may have become deconditioned or “out of shape” for a variety of reasons (including smoking, obesity, heart disease, etc).  A PFT can distinguish what factors may be contributing to the symptoms of breathlessness.


Results in inflammation of the lung tissue. Although it can affect other organs, it is most commonly found in the lungs. This disease should be monitored by your doctor as in some cases it can lead to progressive symptoms and scarring of the lungs.

Chronic Obstructive Pulmonary Disease (COPD)

This is a term used to describe many progressive lung diseases including emphysema, chronic bronchitis, and non-reversible asthma. It causes obstruction of the airflow from the lungs, so air gets trapped in the lungs. Symptoms include breathing difficulty, cough, mucus (sputum) production, and wheezing. It is usually caused by smoking, although working or living in some environments can contribute to COPD as well. 

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