title: Computational fluid dynamics upper airway effective compliance, critical closing pressure, and obstructive sleep apnea severity in obese adolescent girls.
abstract: Obstructive sleep apnea syndrome (OSAS) is associated with anatomical abnormalities restricting upper airway size and functional factors decreasing pharyngeal dilator activity in sleep. In this study we hypothesized that OSAS is also associated with altered pharyngeal mechanical compliance during wakefulness. Five OSAS and six control obese girls between 14 and 18 years of age were studied. All underwent polysomnography, critical closing pressure (Pcrit) studies, and dynamic MRI of the upper airway during awake tidal breathing. Effective airway compliance was defined as the slope of cross-sectional area vs. average pressure between maximum inspiration and maximum expiration along the pharyngeal airway. Pharyngeal pressure fields were calculated by using image-based computational fluid dynamics and nasal resistance. Spearman correlations were calculated to test associations between apnea-hypopnea index (AHI), Pcrit, and airway compliance. Effective compliances in the nasopharynx (CNP) and velopharynx (CVP) were lower and negative in OSAS compared with controls: -4.4 vs. 1.9 (mm2/cmH2O, P = 0.012) and -2.1 vs. 3.9 (mm2/cmH2O, P = 0.021), respectively, suggesting a strong phasic pharyngeal dilator activity during inspiration in OSAS compared with controls. For all subjects, CNPand AHI correlated negatively (rS= -0.69, P = 0.02), and passive Pcritcorrelated with CNP(rS= -0.76, P = 0.006) and with AHI (rS= 0.86, P = 0.0006). Pharyngeal mechanics obtained during wakefulness could be used to characterize subjects with OSAS. Moreover, negative effective compliance during wakefulness and its correlation to AHI and Pcritsuggest that phasic dilator activity of the upper pharynx compensates for negative pressure loads in these subjects.
authors.affiliation: Department of Mechanical Engineering, The Cooper Union for the Advancement of Science and Art, New York, New York; wootto@cooper.edu.
authors.forename: David M
authors.initials: DM
authors.lastname: Wootton
authors.affiliation: Children's Hospital at Montefiore, New York, New York.
authors.forename: Sanghun
authors.initials: S
authors.lastname: Sin
authors.affiliation: Department of Mechanical Engineering, The Cooper Union for the Advancement of Science and Art, New York, New York.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Luo
authors.affiliation: Department of Mechanical Engineering, The Cooper Union for the Advancement of Science and Art, New York, New York.
authors.forename: Alireza
authors.initials: A
authors.lastname: Yazdani
authors.affiliation: Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; and.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: McDonough
authors.affiliation: Albert Einstein College of Medicine, New York, New York.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Wagshul
authors.affiliation: Albert Einstein College of Medicine, New York, New York.
authors.forename: Carmen R
authors.initials: CR
authors.lastname: Isasi
authors.affiliation: Children's Hospital at Montefiore, New York, New York; Albert Einstein College of Medicine, New York, New York.
authors.forename: Raanan
authors.initials: R
authors.lastname: Arens
mesh_terms: D000293:Adolescent; D000403:Airway Resistance; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008170:Lung Compliance; D008954:Models, Biological; D063766:Pediatric Obesity / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D010614:Pharynx / Q000503:physiopathology*; D011312:Pressure; D015656:Respiratory Mechanics; D012212:Rheology / Q000379:methods*; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*
keywords: adolescent; airway compliance; dynamic MRI; human; rhinomanometry