ACCURACY AND REPEATABILITY OF A POCKET TURBINE SPIROMETER - COMPARISON WITH A ROLLING SEAL FLOW-VOLUME SPIROMETER

The accuracy and repeatability of a recently introduced pocket spirometer (Micro Spirometer(c); Micro Medical Instruments Ltd, Rochester, UK) was evaluated. FEV1 and FVC values obtained with this instrument were compared with those measured with a rolling-seal flow-volume spirometer (CPI 220 with microcomputer) in 31 patients and 11 healthy volunteers. In the whole material, expressed as mean +/- SD, the pocket spirometer recorded 0.44 +/- 0.23 l (13 +/- 7%) smaller values for FEV1 (P < 0.001) and 0.64 +/- 0.481 (15 +/- 11%) smaller values for FVC (P < 0.001) than the rolling-seal spirometer. The short-term repeatability of the measurements expressed as the coefficient of variation of repeated measurements using the pocket spirometer was 2.2% for FEV1 and 2.3% for FVC in a series of 10 healthy subjects and 10 patients with COPD. It is concluded that the underestimation of FEV1 and FVC of the pocket spirometer was too large and inconsistent for the device to be used interchangeably with conventional spirometers. However, the repeatability of the measurements with the pocket spirometer is close to that reported previously for flow-volume spirometry. Thus the pocket spirometer may be suitable in assessing acute changes of spirometric indices e.g. during provocation tests or during patient follow-up in asthma.