Abstract
Introduction: Clinical application of the forced oscillation technique (FOT) has recently progressed worldwide with the spread of commercially available broadband frequency FOT devices.The difference between resistance at 5 Hz and 20 Hz (R5-R20) is interpreted as an indicator of small airway function in asthma. However, the relationship between forced oscillatory parameters and the nitrogen (N2) single-breath washout (SBW) test is not fully understood.
Aims and objectives: We hypothesized that spirometry and forced oscillatory parameters would predict independently to the results of the SBW test. In this cross-sectional study we assessed the relationship between the phase III slope (delta N2) derived from N2 SBW and the pulmonary function parameters.
Methods: Spirometry, N2 SBW, and the broadband frequency FOT (MostGraph-01, Chest M.I. Co. Ltd., Tokyo, Japan) were performed in 74 patients with asthma. Multiple regression analyses were performed to determine the predictors of delta N2. Model selection was made by the best subset selection procedure using Akaike's information criteria (AIC).
Results: Univariate analyses revealed that delta N2 correlated positively with age, inspiratory R5, R5-R20, resonant frequency (Fres), and low-frequency reactance area (ALX), and negatively with body mass index, FVC, FEV1, FEF25-75%, and reactance at 5 Hz (X5). In multiple regression analyses, delta N2 was independently predicted by body mass index, FEV1, and inspiratory Fres (R2 = 0.502, p <0.0001). R5-R20 was not selected according to the AIC.
Conclusions: Resonant frequency is a predictor of the degree of ventilation inhomogeneity, a small airway function, derived from N2 SBW in asthma.
- Copyright ©ERS 2015