Spirometry

Spirometry is a simple and widely used lung function test. A spirometry test measures airflow when we breath and can show possible abnormalities in the airways and lung tissue.

On this site we will try to explain the different spirometry tests, the different measurement types used for measuring the flow and on interpreting spirometry and flow-volume loop.

Spirometry is becoming more and more important, as respiratory diseases are increasing rapidly. Spirometry is the method of choice for a quick and reliable screening of obstructive lung diseases like COPD (Chronic Obstructive Pulmonary Disease) and asthma.

evolution COPD
the evolution of mortality of the important chronic diseases:
only COPD mortality is increasing rapidly

Worldwide COPD is mortality cause n° 3 after ischemic heart disease and stroke. In the USA every 4 minutes someone dies from COPD!
Fortunately COPD can be avoided in most cases: 85-90% of COPD cases are caused by tobacco smoking.

It is very important that COPD is discovered as soon as possible. The graph below shows that spirometry is the prefered method for an early screening of COPD. Using spirometry one can discover COPD 10 to 15 years earlier than with the other conventional methods, like symptoms, blood gases and chest X-rays.

copd
diagnosis of COPD using different methods
green: no visible signs, red: very important changes

A drop in the parameters measured by spirometry tests is often the first sign of COPD. The most important parameters are FEV1 (Forced Expiratory Volume in the 1st second), PEF (Peak Expiratory Flow), FVC (Forced Vital Capacity), FEV1/FVC ratio (Tiffeneau index) and FEF25-75 (Forced Expiratory Flow between 25 and 75% of the FVC).

Spirometry is equally important in the diagnosis and follow-up of asthma and other respiratory diseases.

Considering the importance of respiratory diseases on public healthcare and the economy, it is clear that spirometry deserves a lot more attention as it is a simple and inexpensive test.

  • Indications
    Indications for spirometry include assessment of lung function, disability, severity of lung disease and effect of environmental or occupational exposure.
  • Peak Flow
    A well known and often used test in general practice is measurement of Peak Expiratory Flow or peak flow. Peak flow measurement is often used for diagnosing and follow-up of astma.
  • Predicted Values
    Predicted Values in spirometry are used to assess the results of the flow-volume loop. Spirometric valies are compared to the average of a large sample of healthy subjects.
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