scholarly journals Evaluation of human obstructive sleep apnea using computational fluid dynamics

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Shahab Taherian ◽  
Hamid Rahai ◽  
Samuel Lopez ◽  
Jamie Shin ◽  
Behrouz Jafari
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
3D Models ◽  
Ct Scans ◽  
Cfd Modeling ◽  
Apnea Hypopnea Index ◽  
Upper Airways ◽  
Obstructive Sleep

AbstractObstructive sleep apnea (OSA) severity might be correlated to the flow characteristics of the upper airways. We aimed to investigate the severity of OSA based on 3D models constructed from CT scans coupled with computational fluid dynamics (CFD) simulations. The CT scans of seven adult patients diagnosed with OSA were used to reconstruct the 3D models of the upper airways and CFD modeling and analyses were performed. Results from the fluid simulations were compared with the apnea-hypopnea index. Here we show a correlation between a CFD-based parameter, the adjusted pressure coefficient (Cp*), and the respective apnea-hypopnea index (Pearson’s r = 0.91, p = 0.004), which suggests that the anatomical-based model coupled with CFD could provide functional and localized information for different regions of the upper airways.

scholarly journals Noninvasive estimation of pharyngeal airway resistance and compliance in children based on volume-gated dynamic MRI and computational fluid dynamics

2011 ◽  
Vol 111 (6) ◽  
pp. 1819-1827 ◽  
Author(s):  
Steven C. Persak ◽  
Sanghun Sin ◽  
Joseph M. McDonough ◽  
Raanan Arens ◽  
David M. Wootton
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Magnetic Resonance Images ◽  
Cfd Modeling ◽  
Tidal Breathing ◽  
Upper Airways ◽  
Pharyngeal Airway ◽  
Airway Collapse ◽  
Obstructive Sleep

Computational fluid dynamics (CFD) analysis was used to model the effect of collapsing airway geometry on internal pressure and velocity in the pharyngeal airway of three sedated children with obstructive sleep apnea syndrome (OSAS) and three control subjects. Model geometry was reconstructed from volume-gated magnetic resonance images during normal tidal breathing at 10 increments of tidal volume through the respiratory cycle. Each geometry was meshed with an unstructured grid and solved using a low-Reynolds number k-ω turbulence model driven by flow data averaged over 12 consecutive breathing cycles. Combining gated imaging with CFD modeling created a dynamic three-dimensional view of airway anatomy and mechanics, including the evolution of airway collapse and flow resistance and estimates of the local effective compliance. The upper airways of subjects with OSAS were generally much more compliant during tidal breathing. Compliance curves (pressure vs. cross-section area), derived for different locations along the airway, quantified local differences along the pharynx and between OSAS subjects. In one subject, the distal oropharynx was more compliant than the nasopharynx (1.028 vs. 0.450 mm2/Pa) and had a lower theoretical limiting flow rate, confirming the distal oropharynx as the flow-limiting segment of the airway in this subject. Another subject had a more compliant nasopharynx (0.053 mm2/Pa) during inspiration and apparent stiffening of the distal oropharynx (C = 0.0058 mm2/Pa), and the theoretical limiting flow rate indicated the nasopharynx as the flow-limiting segment. This new method may help to differentiate anatomical and functional factors in airway collapse.

scholarly journals Computational fluid dynamics endpoints to characterize obstructive sleep apnea syndrome in children

2014 ◽  
Vol 116 (1) ◽  
pp. 104-112 ◽  
Author(s):  
David M. Wootton ◽  
Haiyan Luo ◽  
Steven C. Persak ◽  
Sanghun Sin ◽  
Joseph M. McDonough ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
Obstructive Sleep Apnea Syndrome ◽  
Sleep Apnea Syndrome ◽  
Nasal Resistance ◽  
Cfd Model ◽  
Obstructive Sleep ◽  
Apnea Syndrome

Computational fluid dynamics (CFD) analysis may quantify the severity of anatomical airway restriction in obstructive sleep apnea syndrome (OSAS) better than anatomical measurements alone. However, optimal CFD model endpoints to characterize or assess OSAS have not been determined. To model upper airway fluid dynamics using CFD and investigate the strength of correlation between various CFD endpoints, anatomical endpoints, and OSAS severity, in obese children with OSAS and controls. CFD models derived from magnetic resonance images were solved at subject-specific peak tidal inspiratory flow; pressure at the choanae was set by nasal resistance. Model endpoints included airway wall minimum pressure (Pmin), flow resistance in the pharynx (Rpharynx), and pressure drop from choanae to a minimum cross section where tonsils and adenoids constrict the pharynx ( dP TAmax). Significance of endpoints was analyzed using paired comparisons ( t-test or Wilcoxon signed rank test) and Spearman correlation. Fifteen subject pairs were analyzed. Rpharynx and dP TAmax were higher in OSAS than control and most significantly correlated to obstructive apnea-hypopnea index (oAHI), r = 0.48 and r = 0.49, respectively ( P < 0.01). Airway minimum cross-sectional correlation to oAHI was weaker ( r = −0.39); Pmin was not significantly correlated. CFD model endpoints based on pressure drops in the pharynx were more closely associated with the presence and severity of OSAS than pressures including nasal resistance, or anatomical endpoints. This study supports the usefulness of CFD to characterize anatomical restriction of the pharynx and as an additional tool to evaluate subjects with OSAS.

Predicting the Treatment Response of Oral Appliances for Obstructive Sleep Apnea Using Computational Fluid Dynamics and Fluid-Structure Interaction Simulations

2013 ◽  
Author(s):  
Moyin Zhao ◽  
Tracie Barber ◽  
Peter Cistulli ◽  
Kate Sutherland ◽  
Gary Rosengarten
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
Pressure Drop ◽  
Treatment Response ◽  
Fluid Structure Interaction ◽  
Maximum Pressure ◽  
Structure Interaction ◽  
Obstructive Sleep

In this study we used computational fluid dynamics (CFD) to analyze the therapeutic effect of an oral device (mandibular advancement splint – MAS, that protrudes the lower jaw during sleep) as a treatment for Obstructive Sleep Apnea (OSA). Anatomically-accurate upper airway (UA) computational models were reconstructed from magnetic resonance images (MRI) of 7 patients with and without a MAS device fitted. CFD simulations of UA airflow were performed at the maximum flow rate during inspiration. The CFD results indicated the lowest pressure often occurs close to the soft palate and the base of the tongue. The airway pressure gradient was estimated as the best indicator for treatment response since the change in the pressure drop forms a linear correlation with the change in patients’ Apnea-Hypopnea Index (AHI). This correlation has the potential to be developed into a model for predicting the outcome of the MAS treatment. However the rigid wall assumption of CFD models is the major uncertainty. To overcome this uncertainty we set up a full fluid-structure interaction model for a typical responder case with a compliant UA wall. The results demonstrated the different UA flow field associated with using MAS alleviated the airway collapse, which was successfully predicted for the untreated patient. We thus show for the first time that FSI is more accurate than CFD with rigid walls for the study of OSA, and can predict treatment response. Comparison of the FSI and CFD results for the UA flow and pressure profiles showed variation between the models. The structural deflection in oropharynx effectively reformed the flow pattern, however, the maximum pressure drops of both results were close. This supports the competence of the CFD method in clinical applications, where maximum pressure drop data can be used to develop a treatment-predicting model.

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