Spirometry

Spirometry

Alternate Names

  • pulmonary function tests
  • Lungs and bronchial tree

Definition

Spirometry refers to tests that use a special machine to measure a person's lung function. It determines how much air a person can exhale, how fast a person can exhale, and how much air a person can inhale.

Who is a candidate for the test?

Spirometry is carried out in a healthcare setting using special equipment. It is helpful for determining the cause of shortness of breath.
The test can be used to diagnose respiratory conditions, including:
  • abnormal blood flow to the lungs, such as pulmonary hypertension
  • chronic obstructive pulmonary disease, including chronic bronchitis and emphysema
  • other respiratory diseases, such as cystic fibrosis
  • reactive airway disease, such as asthma
Once a respiratory problem has been diagnosed, spirometry can be used to monitor response to treatment. It can also be used to gauge whether an individual with lung cancer has enough lung reserve to withstand the surgical removal of the lung or section of lung that contains the cancer.

How is the test performed?

Spirometry is performed using a simple instrument called a spirometer. The person taking the test puts the instrument in his or her mouth. The individual inhales as much air as the lungs will hold, then blows out the air as fast and for as long as possible. The spirometer records the volume that the lungs can exhale. It also measures the speed of exhalation.
The maximum volume ventilation, or MVV, test measures the volume exhaled in 15 seconds. This result is multiplied by four to give the value for one minute.
Both the forced vital capacity, or FVC, test and the forced expiratory volume, or FEV1, test measure the rate and amount of air exhaled in one second.
The individual inhales and blows into the spirometer as hard and fast and long as possible. The procedure is repeated three times and the highest numbers are recorded.

What is involved in preparation for the test?

Spirometry generally requires no preparation, However, the healthcare professional may request that some medications not be taken prior to the test.

What do the test results mean?

A person's spirometer readings from the MVV, FVC, and FEV1 tests are evaluated by comparing them with values from a standard table. The table provides values based on a person's age, sex, and body size.
Abnormal results may indicate the following:
  • exposure to contaminants in the air
  • changes in lung function due to medications
  • lung disease

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