Respiratory impedance in patients with Duchenne muscular dystrophy.

Unlabelled: Impulse oscillometry (IOS) evaluates non-effort-dependent respiratory mechanics, and thus it may be useful to evaluate patients with Duchenne muscular dystrophy (DMD).

Objectives: We aimed (1) to describe the behavior of IOS parameters in patients with DMD, and compare it to those from a control group; (2) to determine whether resistances and reactances differ in relation to the severity of DMD; and (3) to compare IOS parameters with spirometry and maximal inspiratory (MIP) and expiratory (MEP) pressures.

Methods: Children and adolescents (<20 years old) with biopsy-confirmed DMD and age-paired subjects were cross-sectionally evaluated. All results were transformed to z scores with respect to the healthy subjects (reference population).

Results: Anthropometric characteristics did not differ between the 31 patients and 69 controls included in the study. Compared with controls, patients with DMD had higher IOS resistances and lower reactances. As expected, FEV and FVC were lower in patients and always declined as age increased. By contrast, MIP and MEP were lower-than-normal in youngest patients, tended to improve around puberty initiation, and declined thereafter. In general, there was a poor correlation between IOS parameters and spirometric variables or respiratory pressures, excepting for X20 Hz, which had an inverse correlation with FEV . Interestingly, IOS resistances were higher in patients with less disability (lower Vignos score; better FVC), but tended to be normalized in advanced stages of the disease.

Conclusion: This study showed that IOS is feasible in children and adolescents with DMD and yields information about respiratory function not achievable with the usual forced techniques. Pediatr Pulmonol. 2016;51:1072-1079. © 2016 Wiley Periodicals, Inc.