Abstract
BACKGROUND: Individuals with Duchenne Muscular Dystrophy (DMD) exhibit respiratory muscle changes leading to fatigue and weakness, and assessing relaxation rates and contractile properties may help detect early fatigue. AIM: To non-invasively assess inspiratory muscle relaxation and contractile rates using sniff nasal inspiratory pressure (SNIP) parameters in DMD subjects and compare them with matched healthy controls. METHODS: A case-control study of 32 DMD male subjects and 32 age-matched healthy controls (12.7 ± 5.1 years). All subjects underwent spirometry, maximal respiratory pressures, and SNIP test. We calculated the maximum relaxation rate (MRR), decay constant (τ), and maximum rate of pressure development (MRPD) from the SNIP curve. RESULTS: The DMD group had significantly lower MRR (5.9 [5.1-6.9] vs. 8 [6.9-10.3] %/ms, p = 0.001), lower MRPD (-0.38 [-0.47 to -0.26] vs. -0.62 [-0.52 to -0.80] cmH(2)O/ms-1, p = 0.001), and higher τ (65.7 [50.7-78.1] vs. 40.5 [30.2-48.7] ms, p = 0.001). ROC curves showed that SNIP parameters effectively distinguish DMD from healthy subjects (SNIP [AUC 0.94, p < 0.001], MRR [AUC 0.86, p < 0.001], τ [AUC 0.92, p < 0.001], and MRPD [AUC 0.89, p < 0.001]). CONCLUSIONS: DMD subjects show impaired inspiratory muscle contraction and relaxation, indicating early muscle weakness or fatigue. SNIP-derived parameters may help in the early identification of inspiratory muscle dysfunction in DMD, potentially contributing to clinical detection and intervention.