Pulmonary functions according to age evaluated using spirometry and impulse oscillometry in patients with neuromuscular disorders

Purpose: This study investigates the utility of impulse oscillometry (IOS) in patients with neuromuscular disorders (NMDs) who have restrictive lung function, and compares trends in IOS and spirometry parameters.Methods: This study included patients with diagnosed NMDs (Duchenne muscular dystrophy [DMD], spinal muscular atrophy [SMA], and congenital muscular dystrophy [CMD]) who underwent IOS and pulmonary function test (PFT) simultaneously between January 2020 and July 2021.Correlations between linear variables of IOS and PFT were evaluated.Results: A total of 123 patients were enrolled (95 DMDs, 19 SMA, 9 CMD).The absolute values of all IOS values were larger in SMA compared to DMD patients (P< 0.001).Forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were lower in DMD patients, while R5, R20 were larger and X5 were more negative in SMA patients.All parameter, except for FEV1/FVC, decreased as age increases.In IOS parameters plotted across age, when younger, R5, R20, and R5-R20 were higher than predicted, but tended to normalize as age increased.X5 was also lower than expected, indicating larger reactance, but normalizes as patients age.Fres and area of reactance (AX) also decreased across age.FVC and FEV1 were moderately correlated with R5 and R20.FVC and FEV1 were negatively correlated with X5.Conclusion: All volumetric and flow parameters, as well as resistance and reactance, decreased across age, in advanced NMD patients.The results of this study indicate that spirometry and IOS parameters may moderately correlate with volume, flow and resistance, and that IOS can provide reliable information for assessing disease progression in these patients as well.(