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Excessive Daytime Sleepiness: Clinical Considerations
Published in Anthony N. Nicholson, The Neurosciences and the Practice of Aviation Medicine, 2017
Thomas C. Britton, Andrew R. C. Cummin, Anthony N. Nicholson
The pathogenesis of obstructive sleep apnoea syndrome is not fully understood, but the problem arises from recurrent obstruction or narrowing of the pharynx during sleep. Anatomical and functional factors, some genetically determined, combine to cause a loss of pharyngeal patency, perhaps because of craniofacial differences or, especially in the obese, the deposition of fat. The functional element is critical (White, 2005). Patency is maintained during wakefulness as a result of the activity of the pharyngeal dilator muscles, but in sleep, especially rapid eye movement sleep, the normal reduction muscular tone which includes the pharyngeal muscles, in susceptible individuals, causes the pharynx to narrow or become occluded.
Improvements resulting from respiratory-swallow phase training visualized in patient-specific computational analysis of swallowing mechanics
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2018
Thi Tu Anh Tran, Bonnie Martin Harris, William G. Pearson
As the bolus enters the hypopharynx, the rapid elevation of the hyolaryngeal complex marks the onset of the pharyngeal phase of swallowing. The suprahyoid muscles (mylohyoid, geniohyoid, stylohyoid and digastric) displace the hyoid anterosuperiorly, translating force through the thyrohyoid membrane and muscle to assist in elevating the larynx. The stylopharyngeus, attached to the posterior thyroid cartilage, further facilitates laryngeal elevation. The palatopharyngeus and salpingopharyngeus work together to shorten the pharynx and to elevate the larynx (Figure 1). The suprahyoid muscles and the long pharyngeal muscles (stylopharyngeus, palatopharyngeus and salpingopharyngeus) all displace the hyolaryngeal complex comprised of hyoid bone, larynx and associated structures, including the trachea and cricopharyngeus muscle that forms the pharyngoesophageal segment (PES). The net movement of the hyolaryngeal complex displaces the laryngeal inlet of the upper airway from the trajectory of an oncoming bolus contemporaneous with laryngeal vestibular closure resulting from approximation of the arytenoid cartilages to the petiole of the epiglottis and epiglottic inversion (Logemann et al. 1992). Vocal fold adduction is the final mechanism to protect the airway. Prior to laryngeal elevation and pharyngeal shortening and associated pharyngoesophageal segment opening, the cricopharyngeus muscle relaxes and further facilitates PES opening. After the bolus enters the PES, pharyngeal constrictors clear the remaining bolus through the PES thus completing the pharyngeal phase of swallowing.