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A comparative study of the relationship between airway size, tongue activity and body position

University of British Columbia

Airway obstruction in Obstructive Sleep Apnea (OSA) patients is believed to occur in the supine position during sleep. In order to investigate the relationship between upper airway size and genioglossus(GG) muscle activity, up-right (in natural head posture) and supine cephalograms were obtained for twenty OSA and ten asymptomatic control subjects. Tongue EMG and pressure recordings were obtained with the surface electrodes and pressure transducers in ten asymptomatic control subjects. The Student's t test and Wilcoxon signed rank test were used to test for differences between the two groups and between body positions. The OSA group revealed a longer tongue (p< 5%), a larger soft palate (p< 1%), an anteroposteriorly narrower and vertically lengthened upper airway (p< 1%), a inferiorly positioned hyoid bone (p< 1%), a more extended head posture (p< 5%) and a smaller hypopharynx (p< 1%) in the up-right standing position. After changing from the up-right to the supine position, the tongue cross-sectional area increased 4.3% (p< 5%) and oropharyngeal area decreased 3 6.5% (p< 1%) in the OSA group. When comparing the supine to the up-right control cephalograms, changes in tongue area were not observed, but the thickness of the soft palate increased (p< 1%). Differences in tongue cross- sectional area between two groups become significant with body positional changes from the up-right to the supine (p< 1%). With body positional changes, the hyoid bone moves superiorly toward the mandibular plane in the control group (p< 1%), but anteriorly toward the mandibular symphysis in the OSA group (p< 5%). The rest EMG activity of the GG muscle increased 33.8% (p< 5%) and the posterior tongue pressure increased 17% (p< 5%) with body positional changes from up-right to supine. Overall, the orophayngeal cross-sectional area collapsed 28.8% (p< 1%) despite a 34% increase (p< 5%) in GG muscle activity in the asymptomatic control group as a result of body positional changes. Furthermore, a 17% increase of tongue pressure on the posterior load cell indicates positional change of the tongue. In conclusion, it may not be the size of the soft palate alone but also the vertical and anteroposterior position of the tongue which could actively contribute to the development of OSA. Quantification of subtle differences in tongue and oropharyngeal size and position, geometry of the hyoid bone, upper airway muscle activity and tongue pressure accompanied by body positional changes aids in our understanding of the pathogenesis of OSA.

Text

2010-08-22

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http://hdl.handle.net/2429/27612

Dental Science

University of British Columbia

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