Performing spirometry and the importance of properly calibrated spirometers.
Calibration of Spirometers
Before performing spirometry, the equipment used must be calibrated, or at least the calibration checked at the beginning of the session. Depending on the type of equipment, this is achieved using either a 3-L syringe that is pumped through to check that the meter is reading correctly (within a tolerance of 3%) or using a 1-L syringe that is pumped a litre at a time to a maximum of 7 L, which checks the linearity as well as the centre point of the volume measurement.
Many spirometers also allow linear calibration, i.e. the volume is checked at different flows. Some portable meters do not require calibration, for example those that use ultrasound technology. With many meters, the calibration is a checking function and if the calibration is out, the meter needs to be returned to the manufacturer for repair. There is an exception to this where some of the more sophisticated equipment, such as you would find in a lung function laboratory, can update its output based on the calibration. Spirometric values should also be checked on a weekly basis using a biological control (a healthy person working in the laboratory). Flow is very difficult to calibrate and is not calibrated routinely. It requires a sophisticated computer-driven syringe to reproduce forced expiration. Contact us today: 01 866 5727 to have your spirometer calibrated by our experienced engineers.
Occupational Lung Disease
Unit, Dept of Respiratory
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