Spirometry is a pulmonary examination used to diagnose conditions such as asthma and chronic obstructive pulmonary disease (COPD). It measures the amount of air the lungs can hold, as well as how fast they can expel air. During spirometry, a patient breathes through a tube attached to a spirometer, which calculates and records results.

Reasons for Spirometry

Spirometry is used to assess lung function by measuring the amount of air inhaled and exhaled, and the speed of exhalation. It is used both diagnostically and as a means of monitoring chronic conditions, and to check on the effectiveness of treatments in patients with chronic breathing problems.

Spirometry is frequently used for patients with the following conditions:

  • Asthma
  • Bronchitis, or a family history of bronchitis
  • Emphysema, or a family history of emphysema
  • Chronic cough
  • Chronic obstructive pulmonary disease (COPD)
  • Shortness of breath
  • Smoking, or exposure to secondhand smoke

Each measurement process takes just a few minutes to perform, and results can immediately be discussed with the physician. Additional testing may be required to accurately diagnose asthma or other chronic lung conditions.

The Spirometry Test

Spirometry is a common diagnostic test, frequently administered in a pulmonologist's office. In order to get an accurate reading, it is important for the patient to follow directions exactly.

During the test, which takes approximately 15 minutes, the seated patient is instructed to inhale, and then exhale for several seconds into a tube attached to a machine called a spirometer. During the test, a clip may be put on the patient's nostrils to keep them closed. The patient's mouth should form a tight seal with the breathing tube, letting no air escape, and the patient should exhale completely, as hard and for as long as possible.

A typical patient takes the spirometry test three consecutive times to ensure consistent results. While the highest score is used as the final result, if there is too much discrepancy between the values, the patient may be asked to take the test again. Very often, the pulmonologist gives the patient a bronchodilator, which is a medication to open the lungs, between the initial test and the second one, to evaluate whether the medication helps with airflow. There may be up to 15 minutes between tests.

Spirometry Results

Spirometry measurements include two primary results.

Forced Vital Capacity

Forced vital capacity (FVC) is the largest amount of air a patient can forcefully exhale after a deep inhalation. If FVC is abnormally low, it indicates that the patient's breathing is restricted.

Forced Expiratory Volume

Forced expiratory volume (FEV-1) measures how much air the patient can force out of the lungs in one second. It is helpful in evaluating the severity of the patient's breathing problems. An abnormally low FEV-1 reading is indicative of significant lung obstruction.

Risks of Spirometry

Spirometry is a very safe, uncomplicated test. Because of the exertion involved, it may make a patient feel temporarily dizzy or out of breath. For patients with certain heart conditions, or those who have had recent heart attacks, spirometry may be contraindicated. In rare cases, spirometry triggers an episode of severe breathing difficulty.

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