title: Computational fluid dynamics study of the inspiratory upper airway and clinical severity of obstructive sleep apnea.
abstract: The apnea-hypopnea index (AHI) is a widely accepted measure for the severity of obstructive sleep apnea (OSA). Current methods to determine AHI fail to provide anatomic information for treatment decisions. In this report, we studied three-dimensional models of upper airways acquired by computed tomographic scanning with geometric measurements and computational fluid dynamics (CFD) analysis and evaluated the correlations with AHI.Participants had CT scans of their upper airways after standard polysomnography studies. Three-dimensional surface models of upper airways were generated for cross-sectional area measurements of the choanae (ACH) and the smallest cross-sectional area (Amin). Computational fluid dynamic analysis was then performed by using this three-dimensional model. Pressure differences required to set tidal volume during inspiration (ΔPmin-INSP) and expiration (ΔPmax-EXP) and minimum negative pressure produced in the level of ACH (Pmin-INSP at ACH) and Amin (Pmin-INSP at Amin) were calculated. Correlations of these parameters and the body mass index with AHI were analyzed. Statistical differences between groups of different AHI ranges were also compared.The pressure distribution simulated by CFD demonstrated abrupt pressure drops in Amin level, and this phenomenon was more significant in severe OSA. All parameters except ACH and Pmin-INSP at Amin significantly correlated with the AHI, and there were significant statistical differences between the OSA groups and the normal group. The results indicate that, in our study group, the geometry of pharyngeal airway and its CFD simulation correlate well with AHI. This model may be further applied for clinical evaluation.
authors.affiliation: Craniofacial Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Chung-Chih
authors.initials: CC
authors.lastname: Yu
authors.forename: Hung-Da
authors.initials: HD
authors.lastname: Hsiao
authors.forename: Tzu-I
authors.initials: TI
authors.lastname: Tseng
authors.forename: Lung-Cheng
authors.initials: LC
authors.lastname: Lee
authors.forename: Chih-Min
authors.initials: CM
authors.lastname: Yao
authors.forename: Ning-Hung
authors.initials: NH
authors.lastname: Chen
authors.forename: Chau-Jan
authors.initials: CJ
authors.lastname: Wang
authors.forename: Yu-Ray
authors.initials: YR
authors.lastname: Chen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D001239:Inhalation; D007830:Larynx / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D010614:Pharynx / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017286:Polysomnography; D011446:Prospective Studies; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed