Chest
Variations of Respiratory Impedance with Lung Volume in Bronchial Hyperreactivity
Section snippets
Equipment
The measurements were performed with the apparatus (Oscillaire, Jones, United States) developed by Landser et al.9 A pseudo-random-noise signal (4 to 52 Hz in steps of 4 Hz) is superimposed on spontaneous breathing. A Fourier analysis allows the calculation of impedance values from the recordings of pressure and flow at the mouth of the subject, at each of the investigated frequencies. The impedance data are separated in a real part (resistance) and an imaginary part (reactance). To express the
RESULTS
The average values of the impedance data for each group at resting FRC level are given in Table 2. Table 3 shows the coefficients of variation of the one-day or day-to-day intraindividual reproducibility of the impedance and forced expiratory volume and flow data.
The impedance data were correlated with the flow and volume measurements that were acquired a few minutes later. Only the data with a correlation coefficient of 0.50 or higher are shown in Table 4 for each group.
No significant
DISCUSSION
The oscillatory impedance measurements are quite reproducible, especially the real part or resistance and the resonant frequency (CV: 8 to 15 percent). The imaginary part of the impedance or reactance has a lesser reproducibility that is still acceptable. The frequency dependence, however, is poorly reproducible, certainly in the patient groups.
The within-day variability expresses primarily the variability of the man-machine combination (measurement error). The intraindividual reproducibility
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Longitudinal changes in pulmonary function and respiratory impedance of rheumatoid arthritis
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2013, Respiratory Physiology and NeurobiologyCitation Excerpt :Previous studies have largely assessed the within session repeatability and variability of resistance (Gimeno et al., 1993; Neild et al., 1989; Snashall et al., 1991; van Noord et al., 1989). There is very limited data concerning repeatability and variability of Xrs, with published studies having either small numbers of subjects or a limited number of repeat tests (Borrill et al., 2005; Dellaca et al., 2010; Landser et al., 1976; van den Elshout et al., 1990). Our results for repeatability in all 3 groups were similar to, or possibly better than, those reported in the literature.
Respiratory system impedance with impulse oscillometry in healthy and COPD subjects: ECLIPSE baseline results
2011, Respiratory MedicineCitation Excerpt :Compared with the relative stability of FEV1 over short periods (i.e. 3 months), respiratory impedance appears slightly more variable over a similar time frame. This variability is not unique to our study and other investigators have reported intra-individual variability either within-day20,21 or day-to-day.20–22 Van den Elshout20 reported a within-day and day-to-day coefficient of variation (CV) of respiratory system resistance at 8 Hz (R8) of 8.3% and 10.1%, respectively (in comparison, the respective CV for FEV1 was 6.0% and 6.4%).
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2007, Respiratory MedicineCitation Excerpt :This could result in overestimation of d-score in FOT measures. The intra-subject variation of the FOT measures in patients with or without obstruction are reported with coefficients of variation between 10 to 15.2.1,15,16 Thus, the manufacturer of the specific IOS is not recommending repeating measurements.
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2004, ChestCitation Excerpt :The significance of these patterns was tested using the treatment × session interaction, adjusted for age, height, and weight, as shown in Table 5. However, when controlled for tidal volume and respiration rate to eliminate spurious findings (Zrs measures decrease as lung volumes increase during respiration30), only the findings for resistance at 6 Hz remained significant. We found large and highly significant increases in tidal volume and decreases in respiratory frequency during biofeedback in the two groups receiving biofeedback (Fig 2) [treatment × task: tidal volume, F36,1057 = 7.51 (p < 0.0001); respiratory frequency, F36,1050 = 23.35 (p < 0.0001)] (within-group comparisons for biofeedback vs rest periods were significant at p < 0.0001 for the HRV biofeedback groups but were not significant for the two control groups).