Assessment of accuracy and applicability of a portable electronic diary card spirometer for asthma treatment

Abstract

A pocked-sized turbine flowmeter and spirometer device, integrated with an electronic diary card (EDC-spirometer, Micro Medical, U.K.), was tested with a mechanical calibrator, in an outpatient clinic and in the home situation. A screen pneumotachometer was used as flow and volume reference. Ten devices were tested; interdevice variability was small with a mean variation coefficient of 1·1% for both forced expiratory volume in 1 s (FEV 1) and peak expiratory flow (PEF) ( sd 0·5 and 0·4, respectively) for eight settings of the calibrator. Mean difference from reference was −0·131 ( sd 0·04) for FEV 1 (range 0·38–3·16) and 0·091 s −1 ( sd 0·09) for PEF (range 4·2–11·7). No significant deviation from linearity was present. Results obtained in the outpatient clinic confirmed the accuracy of FEV 1 and PEF data obtained with the calibrator. However, linear regression analysis showed a mean underestimation of 0·451 ( sd of estimate 0·29) for forced vital capacity over the whole measurement range, probably due to a restricted integration time. In 10 optimally-treated chronic obstructive pulmonary disease patients in a family practice, PEF measurements were done in the home situation, both with the EDC spirometer and a mini-Wright peak flow meter. No significant differences in the diurnal variation of PEF were found. The PEF data from the mini-Wright meter were corrected for earlier reported flow-dependent systematic deviations. In the home situation, patients preferred the EDC spirometer. It is concluded that this device is applicable in the follow-up and treatment of asthma at home.