Inspiratory Muscle Training in Nemaline Myopathy

Background: Respiratory muscle weakness is a common feature in nemaline myopathy. Inspiratory muscle training (IMT) is an intervention that aims to improve inspiratory muscle strength. Objective: The aim of this controlled before-And-After pilot study was to investigate if IMT improves respiratory muscle strength in patients with nemaline myopathy. Methods: Nine patients (7 females; 2 males, age 36.6±20.5 years) with respiratory muscle weakness and different clinical phenotypes and genotypes were included. Patients performed eight weeks of sham IMT followed by eight weeks of active threshold IMT. The patients trained twice a day five days a week for 15 minutes at home. The intensity was constant during the training after a gradual increase to 30% of maximal inspiratory pressure (MIP). Results: Active IMT significantly improved MIP from 43±15.9 to 47±16.6 cmH2O (p=0.019). The effect size was 1.22. There was no significant effect of sham IMT. Sniff nasal inspiratory pressure, maximal expiratory pressure, spirometry, and diaphragm thickness and thickening showed no significant improvements. Conclusions: This pilot study shows that threshold IMT is feasible in patients with nemaline myopathy and improves inspiratory muscle strength. Our findings provide valuable preliminary data for the design of a larger, more comprehensive trial.