Abnormal patterns of breathing during swallowing in neurological disorders

Swallowing momentarily inhibits breathing, and normally the great majority of apnoeas which accompany a swallow are followed by expiration (xE swallows). This swallowing-breathing interaction is regarded as one of several mechanisms by which the airway is protected from aspiration during swallowing. The purpose of this study was to investigate the interaction of breathing and swallowing in two groups of neurological patients. Twenty-two patients with defined neurological disorders involving various structures or pathways (brain, spinal cord and peripheral nerves) were studied to determine whether particular lesions resulted in breakdown of the normal breathing pattern (22 normal subjects were also assessed and their breathing-swallowing pattern was compared with that of neurological patients). Subsequently, 32 patients with motor neurone disease (MND) were studied to identify factors associated with an abnormal pattern (i.e. swallow apnoeas followed by inspiration) and to clarify whether an abnormal pattern is related to chest infections, episodes of coughing and choking during meals, and prognosis. The swallow apnoea in patients with brain, spinal cord and peripheral neurological diseases was followed by inspiration more frequently than expected [20/22 (91%) patients compared with 2/22 (9%) of normal subjects, P: < 0.001], but this was not associated with a specific site of lesion(s). However, patients with corticobulbar involvement tended to have post-apnoea inspiration more often than those without. MND patients commonly displayed an abnormal pattern during swallowing [14/32 (44%) patients] characterized by inspiration after swallow, prolonged swallow apnoea and multiple swallows per bolus. Over the period of follow-up (12-18 months) this pattern did not predict chest infections, coughing and choking episodes during meals or survival. It seems likely that post-swallowing apnoea inspiration is a non-specific concomitant of disordered swallowing and/or breathing rather than being an important mechanism of aspiration per se or of symptom production.