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Pulmonary Function Testing

Pulmonary function tests are a group of tests that measure how well the lungs take in and release air and how well they move gases such as oxygen from the atmosphere into the body's circulation.

How a pulmonary function test is performed:

In a spirometry test, you breathe into a mouthpiece that is connected to an instrument called a spirometer. The spirometer records the amount and the rate of air that you breathe in and out over a period of time.

For some of the test measurements, you can breathe normally and quietly. Other tests require forced inhalation or exhalation after a deep breath.

Lung volume measurement can be done in two ways:

The most accurate way is to sit in a sealed, clear box that looks like a telephone booth (body plethysmograph) while breathing in and out into a mouthpiece. Changes in pressure inside the box help determine the lung volume.

Lung volume can also be measured when you breathe nitrogen or helium gas through a tube for a certain period of time. The concentration of the gas in a chamber attached to the tube is measured to estimate the lung volume.

To measure diffusion capacity, you breathe a harmless gas for a very short time, often one breath. The concentration of the gas in the air you breathe out is measured. The difference in the amount of gas inhaled and exhaled measures how effectively gas travels from the lungs into the blood.

How to Prepare for the pulmonary function test:

Do not eat a heavy meal before the test. Do not smoke for 4 - 6 hours before the test. You'll get specific instructions if you need to stop using bronchodilators or inhaler medications. You may have to breathe in medication before the test.

How will the Test Make me Feel:

Since the test involves some forced breathing and rapid breathing, you may have some temporary shortness of breath or light-headedness. You breathe through a tight-fitting mouthpiece, and you'll have nose clips.

Pulmonary function tests are performed to:

  • Diagnose certain types of lung disease (especially asthma, bronchitis, and emphysema)
  • Find the cause of shortness of breath
  • Measure whether exposure to contaminants at work affects lung function
  • Assess the effect of medication
  • Measure progress in disease treatment

Pulmonary function test considerations:

The risk is minimal for most people. There is a small risk of collapsed lung in people with a certain type of lung disease. The test should not be given to a person who has experienced a recent heart attack, or who has certain other types of heart disease.

Your cooperation while performing the test is crucial in order to get accurate results. A poor seal around the mouthpiece of the spirometer can give poor results that can't be interpreted.