Coordination of cough and swallow: A meta-behavioral response to aspiration

Abstract

Airway protection is the prevention and/or removal of material by behaviors, such as cough and swallow. We tested the hypothesis that cough and swallow, in response to aspiration, are a “meta-behavior” and thus are coordinated and have alterations in excitability to respond to aspiration risk and maintain homeostasis. Anesthetized animals were challenged with a protocol that simulated ongoing aspiration and induced both coughing and swallowing. Electromyograms of the mylohyoid, geniohyoid, thyrohyoid, thyroarytenoid, thyropharyngeus, cricopharyngeus, parasternal, rectus abdominis muscles together with esophageal pressure were recorded to identify and evaluate cough and swallow. During simulated aspiration, both cough and swallow intensity increased and swallow duration decreased consistent with a more rapid pharyngeal clearance. A phase restriction between cough and swallow was also observed; swallow was restricted to the E2 phase of cough during chest wall and abdominal motor quiescence. These results support the conclusion that the cough and swallow pattern generators are an airway protective meta-behavior. The resulting alterations in swallow drive during the simulated aspiration protocol also supports the conclusion that the trachea provides feedback on swallow quality, informing the brainstem about aspiration incidences. The overall coordination of cough and swallow led to the additional conclusion that mechanically the larynx and upper esophageal sphincter act as two separate valves controlling the direction of positive and negative pressures from the upper airway into the thorax.

Sequential Voluntary Cough and Aspiration or Aspiration Risk in Parkinson’s Disease

“…PD is known to affect the respiratory system [22], and because cough is an overlaid respiratory function, it is not surprising to find changes to the coordination of a sequential cough task in this cohort of PD participants. Recent reports by Pitts et al [23] and Bolser et al [24] assert that cough and swallowing central pattern generators are intricately connected within brainstem centers. Davenport et al [25] hypothesized that brainstem respiratory centers are actually reconfigured to produce cough and swallow behaviors.…”

“…A recent study by Ruddy et al [29] reported an increased CPD and PEFR in three patients with glottal insufficiency who underwent Radiesse ™ Voice injections (Merz Aesthetics, San Mateo, CA, USA). Pitts et al [23] found that expiratory muscle strength training (EMST) improved maximum expiratory pressure and cough peak expiratory airflow in ten patients with PD. Inzelberg et al [30] found increased inspiratory strength (measured as inspiratory pressure generated at the mouth) and endurance in a cohort of 20 participants with mid- to moderate-stage PD following inspiratory muscle training.…”

Measuring voluntary and reflexive cough strength in healthy individuals

“…Pitts et al (2014) demonstrated that coughing strength in cats is greater when the risk of aspiration is larger. This implies that although no dose effect of citric to coughing strength was identified, there is potential for the existence of a dose effect with actual aspiration.…”

Measurement of Voluntary Cough Production and Airway Protection in Parkinson Disease

“…22–24 Functional associations between cough and swallowing function further complicate the clinical presentation. 25–27 …”