Clin Exp Otorhinolaryngol.  2010 Sep;3(3):147-152.

Differences of Upper Airway Morphology According to Obesity: Study with Cephalometry and Dynamic MD-CT

• Kim TH
• Chun BS
• Lee HW
• Kim JS

Abstract

OBJECTIVES
We investigated difference of parameters of polysomnography, cephalometry and dynamic multi-detector computerized tomography (MD-CT) in wake and sleep states according to obesity.
METHODS
We evaluated 93 patients who underwent polysomnography and cephalometry. MD-CT was performed in 68 of these 93 patients. Fifty-nine and 34 patients were classified as obese and non-obese, with obesity defined as BMI > or =25. Cephalometry results were analyzed for 12 variables. Using the MD-CT, we evaluated dynamic upper airway morphology in wake and sleep states and divided the upper airway into four parts named as high retropalatal (HRP), low retropalatal (LRP), high retroglossal (HRG), and low retroglossal (LRG). A minimal cross sectional area (mCSA) and collapsibility index (CI) were calculated for each airway level.
RESULTS
Diastolic blood pressure (P=0.0005), neck circumference (P<0.0001), and apnea-hypopnea index (P<0.0001) were statistically significantly different between the obese and non-obese group. Among 12 cephalometric variables, there was a significant difference in only the distance from mandibular plane to hyoid bone (P=0.003). There was statistical difference in CI of HRG and LRG in sleep state (P=0.0449, 0.0281) but no difference in mCSA in wake and sleep states.
CONCLUSION
The obese group had more severe sleep apnea than the non-obese group. We believe that the increased severity of apnea in the obese group may be have been due to increased collapsibility of the upper airway rather than decreased size of the upper airway.

Keyword

Snoring; Sleep apnea; CT scan; Obesity

MeSH Terms

Apnea
Blood Pressure
Cephalometry
Humans
Hyoid Bone
Neck
Obesity
Polysomnography
Sleep Apnea Syndromes
Snoring

Figure

• 

  Fig. 1 Schematic lateral view of the upper airway. The site of obstruction is classified as one of four levels. The area from the inferior border of the hard palate to the inferior border of the uvula is classified as the retropalate level; the area from the inferior border of the uvula to the superior border of the epiglottis tip as the retroglossal level. Each of these two levels are further divided into 'high' and 'low' levels.HRP: high retropalatal area; LRP: low retropalatal area; HRG: high retroglossal area; LRG: low retroglossal area.

• 

  Fig. 2 Simulated longitudinal display of the oropharynx showing the results of multi-detector computerized tomography in wake and sleep states. coronal: coronal scout view of oropharynx; sagittal: sagittal scout view of oropharynx; phase I: minimal cross-sectional area (mCSA) of oropharynx in wake state; phase II: mCSA of oropharynx in sleep state; phase I*: dynamic imaging of mCSA according to respiration in wake state; phase II*: dynamic imaging of mCSA according to respiration in sleep state; HRP: high retropalatal area; LRP: low retropalatal area; HRG: high retroglossal area; LRG: low retroglossal area. The U indicates uvular levels of oropharynx.

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