Accurate and reliable measurements of spirometry are very important otherwise comparison with reference normal values is meaningless and one would have no confidence that a given result or change in results over time is real. Therefore, the practice of spirometry requires an ongoing program of preventative maintenance and quality assurance:

• Regular cleaning.
• Calibration checks (consult your spirometer manual).
• Equipment maintenance to ensure that the spirometer is operating correctly.
• Regular review to ensure ongoing test quality

A very useful and practical method of assessing the overall performance of the spirometer is to regularly test a healthy subject every week (‘biologic control’). Generally, a variation of more than 5% in FEV1 or FVC should alert you to a problem and the need to have your instrument checked and serviced. Records should be kept of each calibration and the test results from healthy subjects.

Ideally, regular calibration/validation is usually performed with an accurate 3 litre syringe before each testing session.

Infection Control

Precautions must be taken to minimise any risk of cross-infection via the spirometer. The use of low resistance barrier filters significantly reduces the risk of cross-infection and also helps protect the equipment. A new filter must be used for each patient. Re-useable mouthpieces must be cleaned and disinfected between patients. In the case of disposable mouthpieces, a new one must be used for each patient. 

Criteria for Spirometer Performance

The American Thoracic Society (ATS) www.thoracic.org/statements and European Respiratory Society (ERS) www.ersnet.org/ers/ have published comprehensive guidelines on the minimum performance specifications for spirometers.

Content Updated February 2005