Interdevice agreement in respiratory resistance values by oscillometry in asthmatic children

Abstract

Background: With several commercially available devices measuring respiratory impedance by oscillometry, the agreement between values obtained on different instruments or frequencies remains unclear. Our aim was to examine the agreement between resistance and reactance parameters on two oscillometry instruments using different waveforms.

Methods: We conducted a prospective cross-sectional study in asthmatic children aged 3-17 years. Reproducible oscillometry measurements were obtained in random order, by blinded operators, at three modes: 5-10-15-20-25 Hz (5-25 Hz) multifrequency mode on the MasterScreen impulse oscillometry system, and both 5-25 Hz multifrequency mode and 7 Hz monofrequency on the tremoFlo C-100 airwave sinusoidal system. Resistance, reactance and within-breath parameters were examined using the intraclass correlation coefficient (ICC), paired t-test, linear regression and Bland-Altman method.

Results: Of 50 participants, 44 and 38 completed between-device and within-frequency measurements, respectively. Between-device measurements at 5-25 Hz showed high (ICC 0.88-0.91) and good (ICC 0.69-0.87) agreement in resistance and reactance, respectively, but with an absolute within-patient difference (≥0.05 kPa·L-1·s-1) and proportional bias (≥30% per kPa·L-1·s-1) in all parameters and oscillatory frequencies, apart from resistance at 5 Hz. A significant proportional bias was documented in most within-breath parameters at 5 versus 7 Hz on tremoFlo.

Conclusion: Observed differences in resistance and reactance suggest the need for instrument- and frequency-specific paediatric normative values.

Conflict of interest statement

Conflict of interest: F.M. Ducharme reports nonfinancial support (donation of the tremoFlo device) from Thorasys Inc. during the conduct of the study. Conflict of interest: I. Jroundi reports receiving a Canadian Francophonie Scholarship Program (CFSP) postdoctoral scholarship during the conduct of the study. Conflict of interest: G. Jean has nothing to disclose. Conflict of interest: G. Lavoie Boutin has nothing to disclose. Conflict of interest: C. Lawson has nothing to disclose. Conflict of interest: B. Vinet has nothing to disclose.

Figures

FIGURE 1

Patient selection from screening to analysis. IOS: MasterScreen impulse oscillometry system. #: in seven patients, the coefficient of variation of repeated measures exceeded 15%, whereas in one patient, the mean of three values was recorded, but the individual values were lost, preventing confirmation of the coefficient of variation.

FIGURE 2

a–l) Bland–Altman plots of absolute differences between tremoFlo and MasterScreen impulse oscillometry system (IOS) measurements versus the mean of the two measurements in resistance R (left panels) at a) 5, c) 10, e) 15, g) 20, i) 25 and k) 5–20 Hz and in reactance X (right panels) at b) 5, d) 10, f) 15, h) 20, j) 25 and l) 5–20 Hz in 38 patients with reproducible IOS measurements. MD: mean difference. In each plot, the black solid horizontal line represents the absolute within-patient MD between parameters measured on the tremoFlo minus those on the IOS, with 95% of all absolute differences contained within the black dashed horizontal lines. These values are indicated as MD (95% CI) in kPa·L−1·s−1 at the top of each plot: values >0 indicate that tremoFlo measurements were higher than IOS measurements and vice versa. The magnitude and direction of the proportional bias is depicted by the green linear regression line with the 95% confidence interval and is indicated as β (95% CI) at the bottom of each plot.

FIGURE 2

a–l) Bland–Altman plots of absolute differences between tremoFlo and MasterScreen impulse oscillometry system (IOS) measurements versus the mean of the two measurements in resistance R (left panels) at a) 5, c) 10, e) 15, g) 20, i) 25 and k) 5–20 Hz and in reactance X (right panels) at b) 5, d) 10, f) 15, h) 20, j) 25 and l) 5–20 Hz in 38 patients with reproducible IOS measurements. MD: mean difference. In each plot, the black solid horizontal line represents the absolute within-patient MD between parameters measured on the tremoFlo minus those on the IOS, with 95% of all absolute differences contained within the black dashed horizontal lines. These values are indicated as MD (95% CI) in kPa·L−1·s−1 at the top of each plot: values >0 indicate that tremoFlo measurements were higher than IOS measurements and vice versa. The magnitude and direction of the proportional bias is depicted by the green linear regression line with the 95% confidence interval and is indicated as β (95% CI) at the bottom of each plot.

FIGURE 3

a–d) Bland–Altman plots of absolute differences between tremoFlo at 5 and 7 Hz versus the mean of the two measurements in resistance R and reactance X in 44 patients with reproducible measurements for a) R and b) X and in 42 patients for c) ΔR and d) ΔX. MD: mean difference. In each plot, the black solid horizontal line represents the absolute MD, with 95% of all absolute differences contained within the black dashed horizontal lines. These values are indicated as MD (95% CI) in kPa·L−1·s−1 at the top of each plot: values >0 indicate that tremoFlo measurements at 5 Hz are higher than at 7 Hz and vice versa. The magnitude and direction of the proportional bias is depicted by the green linear regression line with the 95% confidence interval and is indicated as β (95% CI) at the bottom of each plot.