Pulmonary function in multiple sclerosis without any respiratory complaints

Objectives Pulmonary complications in severe multiple sclerosis (MS) are often seen secondary to respiratory muscle dysfunction. The development of respiratory muscle dysfunction and its association with disability during the course of MS is unknown. In our study, we investigated the predictive value of respiratory muscle functions and the change in forced vital capacity (Δforced vital capacity [FVC]; FVC upright − FVC supine) to detect deterioration of respiratory muscle functions in the early phase of MS. Patients and Methods Twenty-one MS patients with a median age of 34.5 ± 9.45 years were enrolled. Fourteen cases were relapsing-remitting, six were secondary progressive, one was primary progressive type. The mean duration of disease was 10.76 ± 6.6 years. Seventeen healthy subjects with a median age of 40.7 ± 7.6 years were chosen as a control group. Smoking habit was similar in both groups. Pulmonary function tests (PFT), lung volumes, diffusion, respiratory muscle function (PImax, PEmax), mouth occlusion pressure, and indirect sign of respiratory center function (P0.1) tests were performed. PFT were repeated in supine and upright positions. Results Our results in the MS group and the control group, respectively, were: diffusion (DLCO: 18.8 ± 4.2 vs. 26.4 ± 7.3 mL/mmHg/min), PImax (82.1 ± 26.3 vs. 109.1 ± 23.3 cmH2O), PEmax (119.2 ± 42 vs. 171.8 ± 50.2 cmH2O), P0.1 (2.6 ± 0.7 vs. 4.2 ± 0.7). All parameters were lower in the MS group compared with the control group (p < 0.05). In the MS group, FVC values in the upright position were higher than FVC values in the supine position. The difference in FVC values in MS patients between the upright and supine positions (ΔFVC) was also found to be significantly higher than in the control group (ΔFVC 262.3 ± 247.6 (MS), 98.8 ± 179.1 mL (CONTROL)) (p < 0.01). Conclusion Our results indicate the presence of pulmonary dysfunction in MS even in the absence of any respiratory symptoms.