Computational Simulations of Airflow in an In Vitro Model of the Pediatric Upper Airways

Allen, G. M.; Shortall, B.; Gemci, Tevfik; Corcoran, Timothy E.; Chigier, Norman

doi:10.1115/1.1800554

Cited by 47 publications

(33 citation statements)

References 20 publications

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“…The flow in the obstructed airway models was not as smooth and gradual as in the normal airway model. Similar to the inspiratory flow, jets were formed in the neck of the constricted zones, as consistently predicted in other computational studies [14,43]. Recirculating flows were present in the vicinity of the jet due to boundary layer separation (Fig.…”

Section: Airflow In Normal and Obstructed Airwayssupporting

confidence: 65%

A computational study of the respiratory airflow characteristics in normal and obstructed human airways

Sul

Wallqvist

Morris

et al. 2014

Computers in Biology and Medicine

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Obstructive lung diseases in the lower airways are a leading health concern worldwide. To improve our understanding of the pathophysiology of lower airways, we studied airflow characteristics in the lung between the 8th and the 14th generations using a three-dimensional computational fluid dynamics model, where we compared normal and obstructed airways for a range of breathing conditions. We employed a novel technique based on computing the Pearson׳s correlation coefficient to quantitatively characterize the differences in airflow patterns between the normal and obstructed airways. We found that the airflow patterns demonstrated clear differences between normal and diseased conditions for high expiratory flow rates (>2300ml/s), but not for inspiratory flow rates. Moreover, airflow patterns subjected to filtering demonstrated higher sensitivity than airway resistance for differentiating normal and diseased conditions. Further, we showed that wall shear stresses were not only dependent on breathing rates, but also on the distribution of the obstructed sites in the lung: for the same degree of obstruction and breathing rate, we observed as much as two-fold differences in shear stresses. In contrast to previous studies that suggest increased wall shear stress due to obstructions as a possible damage mechanism for small airways, our model demonstrated that for flow rates corresponding to heavy activities, the wall shear stress in both normal and obstructed airways was <0.3Pa, which is within the physiological limit needed to promote respiratory defense mechanisms. In summary, our model enables the study of airflow characteristics that may be impractical to assess experimentally.

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Section: Airflow In Normal and Obstructed Airwayssupporting

confidence: 65%

A computational study of the respiratory airflow characteristics in normal and obstructed human airways

Sul

Wallqvist

Morris

et al. 2014

Computers in Biology and Medicine

View full text Add to dashboard Cite

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“…The complexity of the human tracheobronchial tree has restricted the majority of previous CFD studies to small regions of the airway tree, with the complex domain represented by idealized cylindrical geometries with simple bifurcations over one to several generations [e.g., (19-21, 66, 115, 116)], or anatomically consistent (but with smoothed circular cross sections) geometry (98). The physical domain has previously been represented on the basis of the classic symmetric Weibel model A (102) or the asymmetric Horsfield model (43); however, it is now possible to compute airflow in physical domains that are anatomically accurate and subject specific [e.g., (3,9,24,25,56,61,113)]. The advantage of this approach is that the influence of anatomical features such as curved airways, cartilage ridges, and diameter variation along an airway can be incorporated correctly.…”

Section: The Interaction Between Geometry and Airflowmentioning

confidence: 99%

Airway Gas Flow

Tawhai

Lin

2011

Comprehensive Physiology

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Local characteristics of airflow and its global distribution in the lung are determined by interaction between resistance to flow through the airways and the compliance of the tissue, with tissue compliance dominating flow distribution in the healthy lung. Current understanding is that conceptualizing the airways of the lung as a system of smooth adjoined cylinders through which air traverses laminarly is insufficient for understanding flow and energy dissipation and is particularly poor for predicting physiologically realistic transport of particles by the airflow. With rapid advances in medical imaging, computer technologies, and computational techniques, computational fluid dynamics is now becoming a viable tool for providing detailed information on the mechanics of airflow in the human respiratory tract. Studies using such techniques have shown that the upper airway (specifically its development of a turbulent laryngeal jet in the trachea), airway geometry, branching and rotation angle, and the pattern of joining of successive bifurcations are important in determining airflow structures. It is now possible to compute airflow in physical domains that are anatomically accurate and subject specific, enabling comparisons among intersubjects, that among subjects of different ages, and that among different species.

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“…To date only the latter two have been used in previous airway CFD studies. 1,3,15,20,33 The impedance BC was proposed and used in the current study by aid of the hypothetical airway tree. For constant pressure BC, the same constant zero pressure was applied at all 13 outlets.…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…1,7,15,33 Few of the previous studies have used both the upper and central airways. To our knowledge, the current study is the first effort to simulate unsteady respiratory flow with anatomically based human large airway models (including upper airway and central airway branches up to generation 6) incorporating impedance (and therefore, time-dependent pressure) boundary conditions.…”

Section: Introductionmentioning

confidence: 98%

An Anatomically Based Hybrid Computational Model of the Human Lung and its Application to Low Frequency Oscillatory Mechanics

Lutchen

2006

Ann Biomed Eng

109

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Lung input impedance measured via forced oscillation over low frequency range has been confirmed as sensitive to the degree and the heterogeneity of lung disease. In this study we advanced an image-based, multi-scale computational model for the human lung, which includes upper and central airways, small airways and alveoli tissue unit. A three-dimensional (3-D) realistic model of the upper airway (reconstructed from MRI images) was combined with an anatomically based 3-D model of the central airways (based on MDCT images) to form a 3-D model of the large airways (from mouth to generation 6, incomplete for generations 4-6). The small airway trees distal to the central branches were based on a hypothetical airway tree for a normal healthy lung. A constant phase viscoelastic model was assumed for the alveolar tissue unit. Unsteady airflows in the large airways were simulated based on computational fluid dynamics (CFD). An experimentally measured broadband forcing flow was applied at the mouth. The impedance of the small airways was computed based on a one-dimensional transmission line model. The computed overall dynamic lung resistance and elastance compared very well with experimental values. Results showed that unsteady 3-D simulation and realistic geometry of the upper and large airways up to generations 4-6 can provide a reasonably accurate estimation of lung input impedance. The impedance of the upper airway constitutes a significant part of the total lung input impedance. The resistance of the upper airway accounts for 45-70% of the total lung resistance at frequencies between 0 and 1 Hz, and 70-81% at frequencies between 1 and 8 Hz.

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Computational Simulations of Airflow in an In Vitro Model of the Pediatric Upper Airways

Cited by 47 publications

References 20 publications

A computational study of the respiratory airflow characteristics in normal and obstructed human airways

A computational study of the respiratory airflow characteristics in normal and obstructed human airways

Airway Gas Flow

An Anatomically Based Hybrid Computational Model of the Human Lung and its Application to Low Frequency Oscillatory Mechanics

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