Spirometry

An overview of spirometry.

Spirometry is a method of assessing lung function. It measures how fast and how much air comes out from the lungs when blown out forcefully.

If the patient’s medical history suggests that there is COPD, spirometry should be performed to confirm the diagnosis.

Key information

Spirometry is a reliable method of differentiating between obstructive airways disorders (e.g. COPD, asthma), restrictive diseases (where the size of the lungs is reduced, e.g. fibrotic lung disease), and mixed types of disorders (where both the obstructive and restrictive features are present e.g Pulmonary Impairment After Tuberculosis – PIAT).
Spirometry also helps to assess severity of airway obstruction, monitor disease progression, and predict the prognosis of disease.
In patients with COPD, post-bronchodilator FEV1/FVC remains <0.7.
However, the FEV1 may improve significantly after bronchodilator, and a change of > 12% AND > 200 mL in FEV1 can occur in around 20% of the COPD patients.
Guidelines recommend that all healthcare professionals managing patients with COPD should be competent in the interpretation of the results of spirometry.
Forced expiratory manoeuvre is commonly practiced in primary care settings. A slow/relaxed manoeuvre is important in patients with more severe disease who trap air when the blow out very hard.