Confronto tra uno spirometro a pistone e uno pneumotacografo con sistema computerizzato

The spirometric parameters obtained by a rolling spirometer (Vicatest Mijnhardt VCT) were compared with those measured by a computerized pneumotachograph (HP 21073A). 60 subjects performed three acceptable forced expiratory manoeuvres with both devices: 30 were subjects with FEV1/FVC% > 70 and 30 were patients with different degree of airway obstruction. Intraobserver variability in the reading of 16 Vicatest spirometric tracings was studied and no difference was found among three readers. Statistical analysis showed that in patients Vicatest FVC was significantly lower than HP FVC; instead FEV1/FVC%, FEF(25-75) and FEF(75-85) were higher when calculated by Vicatest. Moreover, in non obstructed subjects the Vicatest FEV1/FVC% and forced end-expiratory flows were significantly higher than those measured by HP. Through the correlation coefficients (r) were all statistically significant, for many parameters the slope of the regression was significantly different from 1 and the intercept was significantly different from 0. Therefore, Vicatest spirometer proved to be unreliable for measuring the indexes derived from forced vital capacity in patients with airway obstruction; it was also inaccurate for the measurement of the forced expiratory flows in non obstructed subjects.