PMC5476890_01
Mid-sagittal CT sections of the pharynx in patient 1 (a) before UPPP and (b) after UPPP.
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The entire series was loaded into the software, and then the upper airway was identified in each of the axial images based on a predefined threshold of 250 Hounsfield units relative to the surrounding tissue.  Figure 1 shows mid-sagittal sections before (Figure 1(a)) and after (Figure 1(b)) UPPP in the patient.
Three-dimensional model of the upper airway and cross-sectional area data alongside the airway in patient 1. The morphological characteristics of the upper airway are markedly changed after UPPP. However, there is little change in the upper airway volume after UPPP (11.28 cm3 before and 11.78 cm3 after UPPP).
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 Figure 2 shows the cross-sectional area along with the upper airway from the upper end of the velopharynx to the hypopharynx.
Streamlines and contour maps of pressure and velocity before UPPP; (a) pressure contour, (b) flow velocity contour, and (c) streamlines. Low-pressure regions are located at the distal velopharynx, oropharynx, and hypopharynx. At the velopharynx, a high velocity indicates a low static pressure. Vertical recirculation and swirl flow is observed where the airway narrows around the epiglottis between the oropharynx and hypopharynx.
CRIOT2017-2120165.003.jpg
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Figures 3 and 4 show the inhalation flow characteristics and the streamlines and contour maps of the flow velocity and pressure, respectively, before and after UPPP.
Streamlines and contour maps of pressure and velocity after UPPP; (a) pressure contour, (b) flow velocity contour, and (c) streamlines. The complex flow observed before UPPP is inhibited and laminarized after UPPP.
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Figures 3 and 4 show the inhalation flow characteristics and the streamlines and contour maps of the flow velocity and pressure, respectively, before and after UPPP.