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Deling and Simulation of Human Lung

Abbasi, Zeinab | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54362 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Bozorgmehry Boozarjomhery, Ramin
  7. Abstract:
  8. The bronchial tree consists of two main parts: conducting airways and respiratory airways. Parametric Lindenmayer System (L-System) has been used for modeling of the structure. The conducting airways are divided into two parts: central region consisting of trachea up to segmental bronchi and bronchioles located in the bronchopulmonary segments. The boundary of these segments has been found by image processing techniques. Stochastic Parametric L-system has been used for modeling of acinar region. To find the characteristic properties of conducting airways and respiratory bronchioles, an intelligent method has been developed. The parameters of the model are either age dependent or dimensionless which enables the model to be used for modeling of lung structure of various sizes and in various stages of life. The morphometric characteristics of human bronchial tree have been compared with the corresponding measured values and those predicted by previous models. The comparison results indicate that the present method outperforms previous models in both accuracy and computation time. Due to high number of airways in human lung, simulation of transport phenomena based on the whole detailed structure is too time consuming and hence using of reduced order models seems to be inevitable. The previously reduced order models cannot be used for all problems particularly for those in which the asymmetric structure of human lung is important. Prediction of alveolar slope is one of these problems. This study proposes a reduced order model, which combines mechanistic and non-mechanistic approaches and overcomes the limitations of previous models. This model uses the accurate structure developed by L-system and proposes a proxy model for conducting airways and a reduced order model for acini. Combination of these two types of models provides several models for human lung among which the best model can be used for the problem in hand based on the desired accuracy and computational time. The accuracy of the proposed model in the prediction of heterogeneous concentration and asymmetric degree of the human bronchial tree has been evaluated by prediction of alveolar slopes for various breaths. In addition, the ability of the proposed model has been investigated in the simulation of several important problems such as O2-CO2 exchange, hypoxia, hypercapnia, multi breath inert gas washout., Furthermore, estimation of obstructed region in lung, and simulation of inhalation of toxic gases have also been among the problems solved whose results compared against their corresponding measured counterparts. The results reveal that the proposed model is general and robust enough to be used for various problems. In addition, its low computational time enables the model to be used in the clinical centers in an online manner. For instance, the run time of one breath nitrogen washout is ~121hr for accurate one-dimensional model and 4.8s for reduced order model, which can be reduced to 0.18s by multi-thread parallelism approach
  9. Keywords:
  10. Lung ; Hypercapnia ; Hypoxia ; Toxic Gases Inhalation ; Airway ; Oxygen Exchange ; Inert Gas Washout ; Lung Acinar Region ; Conducting Airway

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