ASSESSMENT OF ACCURACY AND APPLICABILITY OF A PORTABLE ELECTRONIC DIARY CARD SPIROMETER FOR ASTHMA-TREATMENT

A pocked-sized turbine flowmeter and spirometer device, integrated wit h an electronic diary card (EDC-spirometer, Micro Medical, U.K.), was tested with a mechanical calibrator, in an outpatient clinic and in th e home situation. A screen pneumotachometer was used as flow and volum e reference. Ten devices were tested; interdevice variability was smal l with a mean variation coefficient of 1 . 1% for both forced expirato ry 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 diffe rence from reference was -0 . 13 1 (SD 0 . 04) for FEV(1) (range 0 . 3 8-3 . 16) and 0 . 09 1 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 dat a obtained with the calibrator. However, linear regression analysis sh owed a mean underestimation of 0 . 45 1 (SD of estimate 0 . 29) for fo rced vital capacity over the whole measurement range, probably due to a restricted integration time. In 10 optimally-treated chronic obstruc tive pulmonary disease patients in a family practice, PEF measurements were done in the home situation, both with the EDC spirometer and a m ini-Wright peak flow meter. No significant differences in the diurnal variation of PEF were found. The PEF data from the mini-Wright meter w ere corrected for earlier reported flow-dependent systematic deviation s. In the home situation, patients preferred the EDC spirometer. It is concluded that this device is applicable in the follow-up and treatme nt of asthma at home.