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Is it useful to perform carbon monoxide diffusion capacity and respiratory muscle function tests in patients with multiple sclerosis without disability?


Ricardo M. Dias, Gaffrée e Guinle Teaching Hospital, Neurology Division, Rua Mariz e Barros, 775 – Rio de Janeiro, 20270-004, Brazil. Email:


Background and objective:  Impairment of respiratory function has been described in end-stage multiple sclerosis (MS), as well as in patients with mild to severe disability. No data are available regarding the respiratory function of MS patients without disability. The objective of this study was to assess the pulmonary function, respiratory muscle strength and carbon monoxide diffusion capacity of the lungs (DLCO) in patients with relapsing-remitting multiple sclerosis (RRMS) without disability.

Methods:  Twenty-seven RRMS patients and 25 healthy control subjects were recruited. All subjects underwent clinical and neurological examination, and spirometry; lung volumes, DLCO and maximal respiratory pressures were measured. All subjects were rated on the Modified Fatigue Impact Scale and Fatigue Severity Scale scales.

Results:  There were no significant differences in age, gender, height, weight or body mass index between the groups. The mean duration of illness in the MS group was 5.44 ± 3.74 years, and the mean Expanded Disability Status Scale was 0.62 ± 0.65. The mean values for total lung capacity, forced expiratory volume in 1 s (FEV1) and FEV1/FVC were normal in both groups. Fifteen RRMS patients exhibited a reduction in maximal expiratory pressure (MEP), but only one patient exhibited a reduction in maximal inspiratory pressure. The mean values for DLCO were lower in RRMS patients (P = 0.0004) than in the control group. DLCO was decreased in 15 (55.55%), out of 27 RRMS patients. The fatigue scale results were not correlated with pulmonary function test results

Conclusions:  DLCO and MEP may be impaired in RRMS patients without disability.