Date on Master's Thesis/Doctoral Dissertation

5-2018

Document Type

Master's Thesis

Degree Name

M.S.

Department

Communicative Disorders

Degree Program

Communicative Disorders, MS

Committee Chair

Pitts, Teresa

Committee Co-Chair (if applicable)

King, Suzanne

Committee Member

King, Suzanne

Committee Member

Mattingly, Rhonda

Committee Member

Smith, Alan

Author's Keywords

mylohyoid; coordination; dysphagia; injury; feline

Abstract

Swallowing motility disorders (dysphagia) are a major complication following radiation treatment for head and neck cancer, affecting ~50% of those treated. One reason for this is that radiation causes muscle damage, provoking sensorimotor pathologies. Previous work has suggested that injury may cause discoordination between breathing and swallowing behaviors. We sought to determine if muscle injury provokes changes in this behavior. We hypothesized that acute suprahyoid muscle damage would alter cross-behavior excitability, causing destabilization of the respiratory-swallow pattern. Swallowing was evoked in anesthetized spontaneously breathing cats via injection of a 3cc bolus of water into the oropharyngeal cavity. A suprahyoid injury was induced unilaterally by applying a ~2mm cryoprobe to the belly of the mylohyoid muscle. Electromyography (EMG) activity (duration, amplitude) was measured concurrently in thyrohyoid, mylohyoid, thyropharyngeal, and diaphragm muscles. Swallow-breathing coordination (SBC) was measured by determining inspiration/expiration phase during the onset and offset of a swallowing event, based off the mylohyoid initiation and thyropharyngeal termination bursts, respectively. Results showed an injury-related effect in the mylohyoid muscle, as indicated by a significant decrease in the mean amplitude post-injury compared to pre-injury. During swallowing, the expiratory phase was found to predominate the respiratory cycle in both pre- and post-injury. No significant changes to the swallow-breathing coordination were found following injury. Results demonstrate that mylohyoid muscle injury does not appear to interfere with short-term changes in the respiratory-swallow pattern. Although deficits in muscle function were found immediately following injury, an extended time or more severe injury may be needed to adversely inhibit these behaviors. Thus, disrupting the stable coupling between respirations and swallowing, which has been found clinically, may not be apparent immediately after injury and require long-term changes in function.

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