Fig. 2
From: Upper airway lengthening caused by weight increase in obstructive sleep apnea patients
Definitions of main parameters on the midsagittal plane. In a, the two lines drawn from the hard palate, near the top of the oral cavity, and the hyoid, which are also normal to the posterior wall, define the two ends of the upper airway. The parameter h, a part of the upper airway length, is the distance from the upper edge of the second cervical vertebra to the hard palate plane. The average thickness of the posterior cervical soft tissue TST is calculated from the area surrounded by the three lines and skin dividing the distance between the two parallel lines passing through the upper and lower edges of the second cervical vertebra. In b, the long axis of the tongue LLAX starts from the central point of the hyoid bone and ends at a point farthest from the hyoid on the tongue surface, and the short axis LSAX is the perpendicular bisector of LLAX ending on the tongue surfaces. The average thickness of the posterior cervical fat TNF is calculated by the area of the fat beneath the skin, from the bottoms of the second to the sixth cervical vertebrae, dividing the length of the central line. In c, The angles α and β represent the relative positions among the occipital bone, cervical vertebra, and nasion: β is the angle between the posterior wall of the upper airway and the occipital bone line drawn from the sellar to the tip of the clivus, and α is the angle between the occipital bone line and the line drawn from the nasion to the sellar. θ is the angle between the posterior wall of the upper airway and the line drawn from the nasion to the sellar. The lower left corner is a magnification of the local region defining these three angles