Analysis of maximum relaxation rate in patients with Duchenne Muscular Distrophy compared to healthy subjects

Slowing in the maximum relaxation rate (MRR) is a reliable index of respiratory muscle fatigue and it is related to weakness. The aim of our study was to assess MRR in Duchenne muscular dystrophy (DMD) and compare to matched-paired healthy subjects. MRR, through non-invasive sniff nasal inspiratory pressure (SNIP), was calculated as the first derivative of pressure with respect to time, normalized by the pressure peak of the same test and expressed as percentage pressure fall per 10ms. We evaluated 15 DMD patients and compared to 15 healthy subjects paired by gender and age (14.7 ± 5.4 years). DMD patients exhibited lung function values lower than healthy subjects (FVC = 1.7 ± 0.6 vs 3.37 ± 1.3 L, p= 0.0002, FEV1 = 1.4 ± 0.7 vs 2.8 ± 1.1 L, p= 0.0003, respectively). Moreover, respiratory muscle strength parameters were significantly decreased in DMD patients compared to healthy subjects (MIP = 56.1 ±18.7 vs 116.4 ±23, MEP = 53.8 ±17 vs 122.7 ±35, SNIP = 53.4 ±20 vs 97.3 ±20.4, respectively, p < 0.001). DMD patients showed a significantly lower MRR than healthy subjects (7 [5.8-8.4] vs 10.1 [7.6-15.1] %/10ms, p = 0.001). We concluded that in DMD patients MRR is decreased, suggesting inspiratory muscle weakness or fatigue.

Source: European Respiratory Journal - November 19, 2018 Category: Respiratory Medicine Authors: Santos, I. P., Lira, M., Medeiros Da Fonseca, J. D., Marques, L., Marcelino, A., Dourado-Junior, M. E., Fregonezi, G., Resqueti, V. Tags: Physiotherapists Source Type: research