Co-ordination of cough and swallow in vivo and in silico

Abstract

Coughing and swallowing are airway-protective behaviours. The pharyngeal phase of swallowing prevents aspiration of oral material (saliva, food and liquid) by epiglottal movement, laryngeal adduction and clearing of the mouth and pharynx. Coughing is an aspiration-response behaviour that removes material from the airway. Co-ordination of these behaviours is vital to protect the airway from further aspiration-promoting events, such as a swallowing during the inspiratory phase of coughing. The operational characteristics, primary strategies and peripheral inputs that co-ordinate coughing and swallowing are unknown. This lack of knowledge impedes understanding and treatment of deficits in airway protection, such as the co-occurrence of dystussia and dysphagia common in Parkinson's and Alzheimer's diseases, as well as stroke.

Figure 1

Is a schematic representation of functional organization of breathing, cough and swallow. The cough, swallow, and breathing pattern generators are controlled and coordinated by one or more populations of neurons called behavior control assemblies (triangle). Receptors in the pharynx, larynx, and trachea provide frequency dependent information to the medulla to initiate behaviors.

Figure 2

Proposed functional organization of the neurogenic model of cough and swallow. Neuronal populations are color coded for their dominant phase of activation during coughing. RLN-recurrent laryngeal nerve, NRM-non-modulated during breathing. The specific identities of neurons participating in behavioral control assemblies are not well understood, but are hypothesized to be outside of the core respiratory network.

Figure 3

Results of a simulation from the current network model producing coughs (stars) and a swallow (triangle). The cough stimulus elicited repetitive coughing. The swallow stimulus elicited one swallow (triangle) at the appropriate phase of the cough cycle, following the cough expiratory burst and before the next cough inspiratory effort (cough E₂).