Spirometry is a way of measuring how well your lungs are functioning. It can be used to diagnose lung disorders, or to test the effectiveness of medication you may be taking for lung-related problems such as asthma.

At The London Clinic, our team of doctors perform spirometry to determine how well your lungs are working. This can be done as an outpatient procedure and is a key part of your lung function test.

What does spirometry measure?

Spirometry is the commonest form of lung function tests. It measures the speed and volume with which your lungs fill up with and expel air when you breathe. The most common measurements for this test are:

  • Forced expiratory volume in one second (FEV1): this measures how much air you can forcibly blow out in one second. In normal healthy lungs, between 70 and 80% of the air in the lungs can be forcibly expelled in this time.
  • Forced vital capacity: this is the amount of air you can fully and forcibly expel in a single breath.
  • Forced expiratory ratio (FEV1/FVC): this is the ratio (proportion) of air blown out in the first second taken as a fraction of the total amount of air that is finally expelled following a forced expiration.
  • Peak expiratory flow (PEF): unlike the above which measure air volume, this measures how fast you can forcibly breathe out, in other words the maximum speed of airflow during expiration.

Why have spirometry?

Spirometry can help your doctor to diagnose and judge the severity of various lung diseases including asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis and pulmonary fibrosis. Spirometry can also be used to assess how well you are responding to treatment for one of these conditions.

Body plethysmography

Body plethysmography is a technique to analyse other aspects of pulmonary function tests. By seating the patient inside a see-through sealed unit that holds a known pressure and volume of air, adjustments can be made to accurately measure the following:

  • Resistance in the airways.
  • Different volumes of air in the lungs (including functional residual capacity and total lung capacity).

This test is completed as part of a full lung function test.