Effects of multiple sclerosis on respiratory functions

Objectives: To measure respiratory functions of ambulatory patients with multiple sclerosis and compare the results with expected values from healthy general population data. Further, to study the correlation of respiratory function impairment with the multiple sclerosis-induced disability level. Subjects: Thirty-eight patients with definite diagnosis of multiple sclerosis from the multiple sclerosis outpatient clinic. Methods: The Expanded Disability Status Scale (EDSS) scores (mean 4.34±1.39) were evaluated to measure disability level. Respiratory functions tested in the laboratory included spirometric (FVC, FEV1, FEV1/FVC), maximal inspiratory (MIP) and expiratory (MEP) mouth pressure measurements. Patients were clinically assessed using a pulmonary dysfunction index (PDI) and dyspnoea index; various breathing features were also recorded. Results: With respect to expected values from healthy general population, important decreases were found in mouth pressures with MIP (77%±23%, p ≃ 0) and MEP (60%±13%, p ≃ 0) while spirometric measures were significantly but less affected (FVC 94%±12%, p < 0.01, FEV1 91%±16%, p < 0.001). FEV1/FVC ratios were normal. Notable increases in PDI (5.58±0.68, p ≃ 0) and dyspnoea index (0.32±0.47, p ≃ 0) were observed. Significant relationships (p < 0.01) between respiratory function impairment and the multiple sclerosis disability level could be detected for FVC, MEP and PDI. Conclusions: Multiple sclerosis clearly impairs respiratory functions; maximal mouth pressures are more severely reduced. This impairment increases with multiple sclerosis-induced disability level but is found to be independent from duration of disease.