Clinical definition of the Spirometry test
Spirometry in simple words means the measurement of breath. A spirometry test is the most popularly used pulmonary function test (PFT) which helps to measure lung function. It measures the amount and speed of air that can be inhaled or exhaled by the lungs. This test helps to diagnose the presence and severity of COPD (chronic obstructive pulmonary disease), asthma, pulmonary fibrosis, cystic fibrosis and some other lung conditions that can cause breathing difficulties. It may also help to monitor the patient’s response to a particular treatment.

Why is the Spirometry test done?
A Spirometry test can be used for a number of reasons:

  • To screen the existence of lung diseases
  • To determining the patient's condition prior to and after a surgery
  • To assess the progress of a lung disease and the effectiveness of the treatment
  • To screen persons at risk for pulmonary diseases such as smokers or persons in occupations with exposures to injurious substances

What are the common signs/symptoms when the Spirometry test is done?

  • Chest pain
  • Cough
  • Difficult or labored breathing
  • Phlegm or bulgum production
  • Wheezing
  • Chest deformity
  • Cyanosis
  • Diminished breath sounds
  • Expiratory slowing

What should I do before the Spirometry test?

Diagnostic procedure

Preparatory instructions before the test *

Soft nose clips may be used during the test to prevent air escaping through the nose

The patient must breathe in fully to take in maximum air possible

Exhale with force for six seconds into a tube like device linked to the spirometer

Results are recorded

Test readings generally taken three times

Do not eat a heavy meal before the test.

Do not smoke for 4 - 6 hours before the test.

*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my Spirometry test results?

Pulmonary function test

Normal value


80% to 120%


80% to 120%

Absolute FEV1 /FVC ratio

Within 5% of the predicted ratio


80% to 120%


75% to 120%


75% to 120%


> 60% to < 120%

FEV1—Forced expiratory volume in one second; the volume of air exhaled in the first second under force after a maximal inhalation.
FVC—Forced vital capacity; the total volume of air that can be exhaled during a maximal forced expiration effort.
FEV1/ FVC ratio—The percentage of the FVC expired in one second.
TLC—Total lung capacity; the volume of air in the lungs at maximal inflation.
FRC—Functional residual capacity; the volume of air in the lungs at resting end-expiration.
RV—Residual volume; the volume of air remaining in the lungs after a maximal exhalation.
DLCO = diffusing capacity of lung for carbon monoxide.
‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’                       

Diseases/conditions related to the Spirometry test

  • Pulmonary diseases
  • Obstructive small airway diseases
  • Interstitial lung diseases
  • Cardiac diseases
  • Congestive heart failure
  • Neuromuscular diseases
  • Guillain-Barré syndrome

Other tests related to the Spirometry test

  • Bronchial challenge test
  • Plethysmography 
  • Nitrogen washout

Synonyms : Pulmonary / Lung function test (PFT)