Cough efficacy is related to the disability status in patients with multiple sclerosis

Background: Cough is an important defense mechanism, whose main function is to remove mucus and/ or foreign bodies from the airways. In patients with multiple sclerosis ( MS), respiratory muscle function may be affected and cough may be impaired. Objectives: Respiratory muscle strength and voluntary cough efficacy were determined in MS patients and controls, and the relationship between cough efficacy and patients' degree of disability was investigated. Methods: We recruited 27 MS patients ( age: 41 +/- 11 years; 18 females) with mild-to-moderate disability, Expanded Disability Status Scale (EDSS) score range: 1-7, and 20 healthy controls ( age: 37 +/- 11 years; 12 females). The maximal inspiratory (PIMAX) and expiratory (PEMAX) pressures, maximal whistle mouth pressures (P-MOW), cough peak flows (CPF), cough expiratory volumes (CEV) and cough gastric pressures (P-GA) were measured in all subjects. Results: In MS patients, the EDSS score was significantly related to CPF, PEMAX, P-MOW, cough P-GA, PIMAX and CEV ( p < 0.01, each correlation). The receiver-operating characteristic curve showed that an EDSS score >= 5.5 was consistent with impaired cough ( CPF <= 5.6 l/s), with a sensitivity of 0.85 and a specificity of 0.95 ( area under curve 0.90, p < 0.001). CPF was related to and predicted by PEMAX, P-MOW, cough P-GA and PIMAX in MS patients ( p < 0.01 each correlation), but not in controls. Conclusions: MS can affect voluntary cough efficacy and respiratory muscle strength, which are inversely related to the patients' degree of disability. In addition, this study shows that CPF is a measure of clinical relevance in MS patients. Copyright (C) 2008 S. Karger AG, Basel.