Paying attention to and ensuring the quality of devices in spirometry labs is of the utmost importance when it comes to producing accurate and usable spirometry results.
At a minimum; a log of calibration results should be maintained, repairs and other alterations should be documented, software and hardware updates or changes should be recorded, and the dates equipment got changed or relocated should be recorded. Most importantly, after any of these situations, calibration verifications should be repeated.
According to the standards determined by the Standardization of Spirometry 2019 Update by American Thoracic Society and European Respiratory Society, spirometry equipment must have a maximum permissible error of equal to or less than 2.5% when tested with a 3-L calibration syringe.
Calibration vs. calibration verification
Calibrating a spirometer includes determining the relationship between flow or volume transducer signals measured by the sensor and the actual flow or volume.
Calibration verification, on the other hand, is the procedure used to confirm that the device is within the limits of calibration, meaning equal to or less than 3% accuracy tolerance, equal to or less than 2.5% for spirometers plus equal to or less than 0.5% for calibration syringes. All spirometry systems must include a calibration verification process that can be done using room air at ambient conditions.
Calibration verifications must be done daily. Precalibrated spirometers such as the SpiroClinic Pro cannot be recalibrated by the operator, but they too should go through calibration verification.
A 3-L syringe used to both recalibrate and verify the volume calibration of spirometers must have an accuracy of equal to or less than 0.015 L or equal to or less than 0.5% of the full scale. The syringe must be kept at room temperature, holding the syringe body to steady the syringe during a calibration verification can raise its temperature and contribute to measurement errors.
Calibration verification must be undertaken at least daily using a 3-L syringe and must be done at least three times, resulting in a range of flows varying between 0.5 and 12 L/s. 3-L injection times should be between 0.5 and 6 seconds.
If an in-line filter is used in spirometry testing, then it must also be used during recalibrations and verifications. The measured volume at each flow must meet the accuracy requirement of equal to or less than 3% for both inspiration and expiration.
- "Standardization of Spirometry 2019 Update". An Official American Thoracic Society and European Respiratory Society Technical Statement, 2019.