Relação entre a função pulmonar e a medida da função motora em pacientes com distrofia muscular de Duchenne

Abstract

Introduction: Duchenne Muscular Dystrophy (DMD) affects skeletal musculature progressively and irreversibly, also affecting the respiratory muscles. Among motor scales, the Motor Function Measure (MFM) favors the understanding of the severity and the monitoring of the evolution of individuals, however, few studies correlate the impairment of functionality with the decline in the strength of respiratory muscles. Objective: Correlate the measurements of respiratory muscle function and strength with functionality by the MFM scale in subjects with DMD. Methods: We evaluated individuals with DMD regarding lung function by spirometry (Forced Vital Capacity - FVC) and maximum inspiratory and expiratory pressures (MIP, MEP, respectively) in addition to nasal inspiratory pressure (SNIP) by manovacuometry. Motor function was assessed by the MFM scale in the dimensions: D1, standing and transfers; D2, axial and proximal motor function; D3, distal motor function; in addition to the full scale value. We used the Kolmogorov-Smirnov test for normality of data and the Spearman correlation to observe the relationships between the variables on the MFM scale and respiratory muscle function and strength. Results: 34 patients (Sex M) aged 13,17 [10,86 – 19,71] were evaluated, BMI 20.18 ± 5.45 kg/m2, FVC(%pred) 74.8 ± 28.2, FEV1(%pred) 63.5 ± 26.8, MIP(%pred) 53.4 ± 19.9, MEP(%pred) 45.3 ± 16.5, and SNIP(%pred) 47.7 ± 17.6. We found a positive and moderate correlation in the Total MFM with FVC(%pred) (r=0.66; p<0.0001), MIP(%pred) (r=0.65; p<0.0001) and MEP(%pred) (r=0.56; p=0.0005). SNIP showed a strong and positive correlation with p<0.0001 in the D1 (r=0.72), D2 (r=0.80) and Total MFM (r=0.76) and moderate with D3 (r=0.68). Conclusion: We conclude that the decline in functionality assessed by the MFM scale in subjects with DMD is positively associated with the decrease in respiratory muscle strength, especially in the inspiratory muscles measured by nasal inspiratory pressure. These findings may favor the introduction of therapeutic interventions early in clinical practice in this population.