Objective: To compare functional exercise capacity, pulmonary function and respiratory muscle strength in fully ambulatory patients with multiple sclerosis with different disability levels and healthy controls, and to elucidate the determinant factors of functional exercise capacity.
Methods: Forty-three fully ambulatory patients with multiple sclerosis and 30 healthy controls were included in the study. Patients were grouped according to Expanded Disability Status Scale (EDSS); Group I (EDSS 0-2), Group II (EDSS 2.5-4.5). Functional exercise capacity was evaluated using a six-minute walk test, and measurement of pulmonary function, and maximal inspiratory and expiratory pressures (MIP, MEP). The Pulmonary Index was used as a clinical predictor of respiratory dysfunction.
Results: Respiratory muscle strength was lower in multiple sclerosis groups compared with controls, but the difference in MIP and %MIP did not reach statistical significance in Group I. The six-minute walk test distance was significantly shorter and peak expiratory flow was lower in multiple sclerosis groups (p < 0.05). Of the variance in the six-minute walk test distance, 75% was explained by EDSS (R2 = 0.55, p < 0.001), difference in heart rate (R2 = 0.06, p = 0.007), age (R2 = 0.05, p = 0.009) and gender (R2 = 0.09, p = 0.003).
Conclusion: Respiratory muscles are weakened, functional exercise capacity is reduced and pulmonary function is affected even in the early phase of multiple sclerosis. Ambulatory patients with multiple sclerosis who have a higher level of disability have lower pulmonary function, respiratory muscle strength and functional capacity than less disabled ones and controls. Neurological disability level, age, gender and heart rate difference on exertion are the determinants of functional exercise capacity.