Pulmonary Function Tests: Overview, Indications and Risk

Pulmonary Function tests are a group of tests used to find out whether your lungs are functioning properly or not. Lung function test is another name given for this test. Physicians order these tests if you have some problems in your lungs like shortness of breath, wheezing, recurrent cough and the results help in making out the exact diagnosis.

Indications of Pulmonary function test

These tests basically measure how effective and how hard your lungs are working to move the air in and out. So, a physician will order these tests to

• Diagnose the condition
• To find the progression of the condition whether it is stable, worsening, or improving.
• If the condition is diagnosed, then how well your lungs are responding to the treatment.

Presenting symptoms of the patient

• Shortness of breath
• Recurrent cough
• Wheezing or abnormal sound during breathing

For diagnosis of diseases like

• Asthma
• Bronchiectasis:  Permanent dilation of the airways in the lungs
• Chronic Bronchitis: Prolonged inflammation of the airways
• Emphysema: Dilation of air sacs of lungs
• Lung cancer
• Asbestosis: Due to prolonged exposure to asbestos

Components of a pulmonary function test

There are many tests that come under the pulmonary function test and all tests are not done for an individual. Only required tests are performed on the basis of the patient history and different people may have different sets of tests. So, the most common of these tests are-

• Spirometry: It measures the volume of air your breath in and out. Thus measuring various volumes and capacities associated with your lung can be used to measure how much air you can expire in a unit of time which is used to assess the narrowness of the airways. The patient inserts a mouthpiece in his mouth which is connected to a machine through a pipe. You have to breathe in and out of that machine and that machine measures the volume on a graph. A nose clip is provided to ensure that you breathe only through the mouth during the procedure. The laboratory person will pleasantly guide you through the steps.
• Peak expiratory flow (PEF): It measures how hard your lungs can force the air out. You breathe through a mouth instrument that has a rotating fan. Your expired air passes through that fan and the highest velocity of that rotating fan is then correlated with the standards.
• Plethysmography test:  The plethysmograph will measure the volume of the lungs by measuring the relative changes in the volumes and the pressure.
• Diffusion capacity test: This test measures how well the air is able to diffuse through the lung alveoli (air sacs present in the lungs) into the blood. It uses various gases like carbon dioxide, helium, or oxygen.

There are many other tests but they are used specifically as per the patient condition.

Risks of Pulmonary functioning testing

Pulmonary functioning tests are normally safe tests with only mild difficulty while performing spirometry. Some tests require some effort so it can create problems in people who have: –

• Recent heart attack
• Severe respiratory illness
• Recent Eye or abdominal surgery

Preparation before test

Generally, the patient is advised to follow the following advice-

• Not to take a heavy meal in the morning, it will make your breathing difficult
• Should wear loose clothes, it will help you to breathe easily.
• Your physician will advise you whether you should take the prescribed medicine or not on the day of the test

What type of doctors orders Pulmonary functioning tests?

These are usually performed by a Pulmonologist or Lung specialist but can also be performed by Primary care physicians.