Stability of the EasyOne ultrasonic spirometer for use in general practice

Objective and background: Spirometry is recommended for the diagnosis and management of chronic respiratory diseases in the community. Spirometer accuracy is critical, but few general practitioners meet the American Thoracic Society and European Respiratory Society (ATS/ERS) recommendation for daily calibration. The aim of this study was to assess the accuracy and stability of a portable ultrasonic spirometer (EasyOne) that the manufacturer claims does not require regular calibration. Methods: Six EasyOne spirometers were used in a practice-based spirometry study. Inspiratory and expiratory accuracy was checked periodically using a certified 3-L syringe. Paired calibration checks were performed using a dedicated mouthpiece assembly (spirette) and randomly selected spirettes. Results: The six spirometers were used for up to 26 weeks (mean 23.9 weeks) and a total of 1041 spirometry tests and 75 syringe calibrations were performed. All inspiratory and expiratory calibration checks using a dedicated or randomly selected spirette met the ATS/ERS accuracy criterion (3.00 +/- 0.105 L). The mean (range) expiratory volume deviation from target volume (3.00 L) was 0.011 L (-0.06-0.09 L) using a dedicated spirette and 0.046 L (-0.09-0.10 L) using randomly selected spirettes. The deviation from target was not affected by the mean flow generated during the calibration procedure. There was no change in calibration during the study. Conclusion: This study supports the manufacturer's claim that the EasyOne spirometer maintains its calibration during routine clinical use in general practice and does not require daily calibration as specified in international spirometry guidelines.