Breathing and Swallowing Pattern Abnormalities in Multiple Sclerosis

Background: Recent data suggest a high prevalence of dysphagia and recurrent aspiration in moderately and severely disabled multiple sclerosis patients. Methods: The study participants included 60 healthy subjects, median age 47 years and 20 moderately to severe disabled patients with multiple sclerosis, presenting with a median EDSS of 5.75 (median age 48 years). A 2-channel computer-assisted system was used to obtain concurrent respiratory and submental surface electromyography signals. Subjects were seated in an upright position and asked to swallow boluses of 5, 10 and 25ml water and 5ml applesauce presented in random order. Eight swallows of each bolus volume and viscosity were recorded. For each swallow, (1) the latency between the onset of swallowing and swallowing apnea (SA); (2) the duration of each SA; (3) the duration of the submental activity, and (4) the pattern of breathing before and after each SA was evaluated. Results: In healthy subjects and patients a total of 2.560 swallows was performed. The latencies between the onset of swallowing and SA were significantly reduced in MS patients. In the patient group the durations of SA and submental activity were significantly prolonged (ANOVA, p<0.001) at all bolus volumes and correlated significantly (r=0.76, p<0.0001). Expiration/inspiration before SA occurred in healthy subjects in 87.3%/12.7% and in patients in 89.4%/10.6% (n.s.). Expiration/inspiration after SA occurred in healthy subjects in 98.9%/1.1% and in patients in 93.0%/7.0% (p<0.0001). The difference was highly significant at all bolus volumes and viscosities. Conclusion: Our study confirms that the great majority of swallowing apneas in healthy subjects are followed by expiration. However, in multiple sclerosis patients the SA is followed by inspiration more frequently than expected which might increase the risk of aspiration or laryngeal penetration. Furthermore, the durations of SA and submental swallowing activity are significantly increased. The prolonged SA duration most probable reflects a protective mechanism owing to the prolonged swallowing activity in multiple sclerosis patients. Our findings indicate a disturbed temporal coordination between respiration and swallowing in multiple sclerosis patients.