Taking Care of Your Lung Health: Pulmonary Function Testing

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Some information provided by Medicine Plus.

Pulmonary function tests measure how well the lungs take in and exhale air.  It also helps to determine how efficiently the lungs transfer oxygen into the bloodstream.  This test is helpful in diagnosing certain types of lung disorders such as asthma and/or chronic obstructive pulmonary disease (COPD).

How The Test Is Performed

By measuring how much air you exhale, and how quickly you exhale, spirometry can evaluate a broad range of lung diseases. In a spirometry test, while you are sitting, 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. When standing, some numbers might be slightly different.

For some of the test measurements, you can breathe normally and quietly. Other tests require forced inhalation or exhalation after a deep breath. Sometimes, you will be asked to inhale a different gas or a medicine to see how it changes your test results.

Lung volume measurement can be done in two ways:

  • The most accurate way is called body plethysmography. You sit in a clear airtight box that looks like a phone booth. The technologist asks you to breathe in and out of 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.

How to Prepare For the Test

If you’re on medications that open your airways, such as those used for asthma or bronchitis, your doctor may ask you to stop taking them before the test. If it isn’t clear whether or not you should take your medication, make sure to ask your doctor. Pain medications may also affect the results of the test. It may be suggested that you do not eat a heavy meal before the test. If you’re a smoker, do not smoke 4-6 hours before the test. Don’t worry, you’re in good hands – you will get specific instructions before the test is performed.

Why the Test is Performed

Pulmonary function tests are done to:

  • Diagnose certain types of lung disease, such as asthma, bronchitis, and emphysema
  • Find the cause of shortness of breath
  • Measure whether exposure to chemicals at work affects lung function
  • Check lung function before someone has surgery
  • Assess the effect of medication
  • Measure progress in disease treatment

Results

Normal values are different from person-to-person. The differences are based on your age, height, ethnicity, and gender. Normal results are expressed as a percentage. A value is usually considered abnormal if it is approximately less than 80% of your predicted value.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results. Abnormal results could potentially mean that you may have chest or lung disease. Some lung diseases (such as emphysema, asthma, chronic bronchitis, and infections) can make the lungs contain too much air and take longer to empty. These lung diseases are called obstructive lung disorders. Other lung diseases make the lungs scarred and smaller so that they contain too little air and are poor at transferring oxygen into the blood. Examples of these types of illnesses include:

  • Extreme overweight
  • Pulmonary fibrosis (scarring or thickening of the lung tissue)
  • Sarcoidosis and scleroderma

Muscular weakness can also cause abnormal test results, even if the lungs are normal, that is similar to the diseases that cause smaller lungs.

After your test is completed, your healthcare provider will talk with you about your test results. It’s time to take control of your health and get tested. Contact us for more information or to schedule an appointment.

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