Cross-System Integration of Respiration and Deglutition: Function, Treatment, and Future Directions

Swallowing occurs preferentially in the expiratory phase of the quiet breathing cycle and at mid-to-low tidal volume. This coordinative pattern imparts important biomechanical advantages to swallowing and airway protection and facilitate laryngeal elevation, laryngeal vestibular and vocal fold closure, and cricopharyngeal sphincter opening. This preferred coordinative relationship between breathing and swallowing is impaired in a variety of patient populations, including head and neck cancer survivors with dysphagia. We developed a training protocol to re-establish more optimal phasing of swallowing with breathing in these patients with striking outcomes, including reduced swallowing physiological impairments and improved airway protection. This motivated us to continue to refine and expand this training protocol and develop new assistive technologies for swallowing monitoring outside of the lab. In this review, we highlight the origins of our optimal respiratory-swallowing coordination hypothesis, describe the biomechanical advantages it provides, carefully describe our training protocol and findings, and chart a course for the next phase of this work. Our overall goal is to harness technology combined with carefully constructed learning paradigms to improve the lives of patients with impaired respiratory-swallowing coordination consequent to a variety of pathologies including head and neck cancer and degenerative neurological conditions such as Parkinson's disease.