Background: The impulse oscillation system (IOS) measures respiratory impedance (Zrs) in terms of resistance (Rrs) and reactance (Xrs) at multiples of 5 Hz. These measurements can be used clinically to help diagnose and monitor respiratory disorders, independent of effort.
Methodology: The predictive equation for resistance at 5 and 20 Hz and impedance at 5 Hz (R5, R20, X5), for the first time, in 299 Japanese adult subjects was determined. In addition, the within single day variation and between day variation were determined.
Results: The predictive equation for R5, R20 and X5 revealed a clear difference with respect to the subject's smoking history (lifelong non-smoker, n = 166, adjusted r = 0.55, 0.46 and 0.57, respectively, vs. smoker, n = 133, adjusted r = 0.47, 0.42 and 0.47, respectively). This difference was less obvious with respect to gender (female, n = 120, adjusted r = 0.42, 0.20 and 0.47, respectively, vs. male, n = 179, adjusted r = 0.46, 0.37 and 0.47, respectively). The predictive equations were dependent on the log of height (H) for both R5 and R20, and on age and log of height for X5. The equations were: R5 (KPa/L/s) = -3.841167 x logH + 8.671580; R20 (KPa/L/s) = -2.546561 x logH + 5.841867; and X5 (KPa/L/s) = -0.000097 x Age + 1.018597 x logH - 2.343672. For these parameters there were no statistically significant differences for within day repeatability or between day variations (P > 0.05), suggesting a high degree of reproducibility for IOS measurements.
Conclusion: It was possible to determine a predictive equation and confirm a high degree of reliability of IOS parameters in Japanese adult subjects.