Correlation between respiratory muscle strength, diaphragmatic mobility and physical activity level in individuals with spinal cord injury

Abstract

Introduction: Spinal cord injury (SCI) causes significant health damage to individuals and can have consequences for different body systems, including the respiratory system. The degree of impairment of functions depends, among several factors, on the level of the spinal segment that was affected. Objective: To verify whether there is a correlation between diaphragmatic function and respiratory muscle strength in individuals with SCI. Methods: Cross-sectional study with 33 individuals with SCI between T1 and L2. To assess diaphragmatic function, measurements of diaphragmatic mobility in tidal volume (cm) and maximum volume (cm), and
thickening fraction (ultrasonography) were taken. Respiratory muscle strength was assessed by measuring maximum inspiratory (MIP; cmH20) and expiratory (MEP; cmH20) pressures (manovacuometry). Pearson's correlation coefficient was calculated to identify the correlation between the outcome variables and the independent variables. Linear regression models were created to investigate the influence of respiratory muscle strength on diaphragmatic function. Results: The thickening fraction did not correlate with any of the independent variables considered in the study. MIP showed a medium and statistically significant
negative correlation with maximum diaphragmatic mobility (r = -0.375; p = 0.031) and a large and statistically significant negative correlation with diaphragmatic mobility in tidal volume (r = -0.558; p = 0.001). The result of the linear regression demonstrated that it can be assumed that there is a significant influence of MIP in maximum diaphragmatic mobility (F(1, 31) = 5.084, p = 0.031; R2 = 0.141), as also demonstrated for diaphragmatic mobility in tidal volume (F(1, 31) = 14.025, p = 0.001; adjusted R2 = 0.311). Conclusion: In people with SCI, inspiratory muscle strength is correlated with maximal diaphragmatic mobility and tidal volume, but not with thickening fraction.