[Evaluation of airway narrowing by MostGraph and spirometry -examination using a reversibility test-]

MostGraph is an apparatus for measuring respiratory resistance and respiratory reactance, using the forced oscillation technique. Because these parameters are measured during tidal breathing of subjects, measuring technique is easy with little burden on subjects. In the present study, we conducted spirometry and MostGraph at the same time and examined the clinical significance of parameters of MostGraph.

Subjects were 52 out-patients who underwent a reversibility test. Spirometry and MostGraph are simultaneously practiced both before and after short acting β2 agonist (SABA) inhalation.

Between each parameter of both methods before SABA inhalation, we confirmed significant correlations between many indexes of both manners. Above all, the strongest correlation was found between Fres and FEV1. In relationships between the percent changes of each parameter of both techniques by SABA inhalation, we also found a significant correlation between percent change of Fres and that of FEV1. In addition, there was a hyperbolic relation between change in Fres and that in FEV1 by SABA inhalation.

We confirmed not only that airway narrowing itself significantly correlates with Fres, but also that elastic resistance of respiratory system changes in association with change of airway narrowing. Thus, our findings suggest that the percent change of Fres may provide a diagnostic criterion for a reversibility test in all parameters of MostGraph.