Various reduced-order surrogate models for fluid flow and mass transfer in human bronchial tree.

Online terrain estimation for autonomous vehicles on deformable terrains

Objective To monitor and treat intrinsic positive end -expiratory pressure (PEEPi) in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and respiratory failure (RF) during mechanicalventilation. Methods End-expiratory airway occlusion technique was used to measure the level of PEEPi in 27 patients with AECOPD and RF during mechanicalventilation. Extending expiratory time,inhalating bronchial dilator, using PEEPe were applied to observe their effects on total PEEP(PEEPt), peak airway pressure(Ppeak), hemodynamics, and gas exchange. Results The levers of PEEPi in 27 patiens with AECOPD during mechanic ventilation were (7±4)era H2O. Changed I: E to 1:2.5 and inhaled bronchial dilator,the PEEPi declined significantly by 11.3% (P 0.05), PaO2 increased and PaCO2 decreased, when PEEPe equal 75% PEEPi, PaO2 increased significantly and PaCO2 decreased significantly(P 75% PEEPi)inereased the danger of barotraumas and had adverse effects onhemedynamies, also had no advantage in lung's gas exchange. Conclusion ①It was common that PEEPi existed in patients with AECOPD and RF during mechanical ventilation.②Extending expiratory time and inhalating bronchial dilator may significantly decrease PEEPi and improve gas exchange. ③Low PEEPe(≤75% PEEPi)may improve the gas exchange,in the meanwhile may not affect respiratory dynamics and hemodynamics. Key words: Acute exacerbation of chronic obstructive pulmonary disease; Intrinsic positive end-expiratory pressure

To study the effect of local airway obstruction on gas exchange, balloon catheters were inflated in segmental, lobar, or left main bronchi. Three techniques were used: an inert gas method to determ...

We consider control and design for coupled, multiphysics systems governed by partial differential equations (PDEs). The numerical solution of the control problem involves large systems of ordinary differential equations arising from a spatial discretization scheme, which can be prohibitively expensive. Utilizing reduced order surrogate models evolved as a way to circumvent this computational problem. While many reduced order models work well for simulation, the task of control adds additional complexity. We investigate the effects of different reduced order models on the optimal feedback control. We propose to use a structure-preserving surrogate model, constructed by computing dominant subspaces for each physical quantity separately. This method addresses the different scaling of variables commonly found in multiphysics problems. As a test example, a coupled Burgers' equation multiphysics PDE model is considered. In the numerical study, we find that the feedback gains obtained from the standard proper orthogonal decomposition for the combined variables fail to converge, while the physics-based method produces convergent control feedback matrices.

The pulsating airflow through human bronchial tree is of great significance for understanding its function and morphology. Fractal theory and numerical simulation are applied in this paper to study the global and local flow characteristics in the bronchial tree under unstable conditions. First, the pulsating flow impedance of fractal bronchial tree is derived, and the structure of bronchial tree is optimized by minimizing flow impedance. It has been shown that the optimal structure depends on the physical law governing the airflow. The optimized diameter ratio between parent and daughter branches for pulsating flow is different from Murray’s law, and the fractal dimension for branch diameter lies in 2 and 3. Afterwards, the local pulsating flow field by three-dimensional (3D) numerical simulation on a symmetrical bronchial model is compared with the global flow characteristics by fractal analysis. The numerical results show that asymmetrical airflow characteristics can be found at high Reynolds number, and the velocity distribution of the main bronchus is more irregular and the turbulence phenomenon is more evident. This work can help to understand the association between function and structure of the bronchial tree, and it may shed light on the physical mechanisms and drugs targeting of pulmonary disease.

The goal of the study is the analytical design of the full asymmetric human bronchial tree (irregular dichotomy) for healthy patients and patients with obstructive pulmonary diseases. For this purpose, the author has derived the special analytical formulas. All surfaces of the bronchial tree are matched with the second-order smoothness (there are no acute angles or ribs). The geometric characteristics of the human bronchial tree in the pathological case are modeled by a “starry” shape of the inner structure of the bronchus; a level of the pathology is defined by two parameters: bronchus constriction level and level of distortion of the cylindrical shape of the bronchus. Closed analytical formulas allow a researcher to construct the human bronchial tree of an arbitrary complexity (up to alveoli); moreover, the parametric dependences make it possible to specify any desirable level of airway obstruction.

Objective To study the bronchial provocation tests before and after the small airway function in patients with chronic cough,airway resistance,and the status of the extrathoracic airway reaction. Methods Sixty-eight patients with chronic cough were histamine bronchial provocation tests, observation FEV1,mid expiratory flow rate(MEF50) the change of the mid and suction flow rate (MIF50),and applies the patients before and after the forced oscillation technique determination inspire airway resistance. Results Bronchial provocation tests positive rate 52%,arouse positive patients before MEF50,R0 patients with negative group difference was statistically significant.MEF50 excitation after/ before ratio(MEF50%)and FEV 1,stimulate after/before ratio(FEV 1%) were positively correlated,and R0 stimulates the difference before and after the negative correlation(R0-d).Thirteen patients present external chest high reaction(accounts for 20% of total cases),among them 6 cases to exist alone external chest high response,7 cases of patients with airway hyperresponsiveness bronchial merger. Conclusions To observe change of small airway function in patients with chronic cough,is helpful to early diagnosis and treatment of asthma.Proocation tests joint observation of bronchial airway responses and extrathoracic airway reaction,can provide clues for clinical diagnosis. Key words: Chronic cough; Bronchial provocation tests; Small airway function; External chest high response

Objective To analyze the characteristics of small/large airway function and eosinophilic inflammation in adult patients with chronic cough and bronchial hyperresponsiveness (BHR), and to explore if that small airway dysfunction was associated with large airway function, inflammation and BHR. Methods Chronic cough patients (16-80 years) with positive methacholine provocation reactivity and spirometric results were enrolled in this single-center cross-sectional study.Provocation reactivity, spirometric results, forced mid-expiratory flow at 25% to 75% of forced vital capacity (FEF25%-75%) and fractional exhaled nitric oxide (FeNO) were collected.The difference between normal small airway function group and dysfunctional group in forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC, peak expiratory flow (PEF), FEV1 after provocation, cumulative dose of methacholine provoking a 20% decrease in FEV1 from baseline value (PD20-FEV1) and FeNO was investigated.Correlation between small airway dysfunction and the above clinical features were also analyzed. Results Totally 96 patients were enrolled.76.04% of patients with chronic cough and BHR had small airway dysfunction.FEV1, FEV1/FVC and PEF decreased significantly in group with small airway dysfunction, companied with more serious increase of BHR.FVC and FeNO had no significant correlation with small airway function. Conclusions Small airway dysfunction may be involved in the development of BHR in patients with chronic cough, independently of airway eosinophilic inflammation.The assessment of small airway function combined with eosinophilic analysis could be considered in prediction of BHR. Key words: Asthma, bronchial; Fractional exhaled nitric oxide; Small airways function; Bronchial provocation; cough

We address a three-tier numerical framework based on nonlinear manifold learning for the forecasting of high-dimensional time series, relaxing the "curse of dimensionality" related to the training phase of surrogate/machine learning models. At the first step, we embed the high-dimensional time series into a reduced low-dimensional space using nonlinear manifold learning (local linear embedding and parsimonious diffusion maps). Then, we construct reduced-order surrogate models on the manifold (here, for our illustrations, we used multivariate autoregressive and Gaussian process regression models) to forecast the embedded dynamics. Finally, we solve the pre-image problem, thus lifting the embedded time series back to the original high-dimensional space using radial basis function interpolation and geometric harmonics. The proposed numerical data-driven scheme can also be applied as a reduced-order model procedure for the numerical solution/propagation of the (transient) dynamics of partial differential equations (PDEs). We assess the performance of the proposed scheme via three different families of problems: (a) the forecasting of synthetic time series generated by three simplistic linear and weakly nonlinear stochastic models resembling electroencephalography signals, (b) the prediction/propagation of the solution profiles of a linear parabolic PDE and the Brusselator model (a set of two nonlinear parabolic PDEs), and (c) the forecasting of a real-world data set containing daily time series of ten key foreign exchange rates spanning the time period 3 September 2001-29 October 2020.

A diameter-based reconstruction of the branching pattern of the human bronchial tree Part II. Mathematical formulation

To assess the distribution of gamma delta T-cells in the human bronchial tree; and to compare quantitatively the differences between gamma delta T-cell numbers in different parts of the airway wall in smokers and non-smokers. Full thickness bronchial wall sections were taken from 10 whole lung specimens from both smokers and non-smokers. Serial cryostat sections stained with the monoclonal antibodies CD3 and TCR delta-1 were examined with the aid of interactive image analysis to assess gamma delta T-cell numbers both in absolute terms and as a proportion of total T lymphocyte numbers. In all cases gamma delta T-cells were demonstrable throughout the airway wall. Although in absolute terms they tend to occur predominantly in the bronchial epithelium, this seems to reflect higher numbers of T lymphocytes in the epithelium in general compared with the submucosa. No genuine epitheliotropism is evident. Comparison by smoking status shows a significant increase in gamma delta T-cell numbers in the bronchial glands of smokers compared with non-smokers. gamma delta T-cells form an integral though variable component of the immunocompetent cell population of the human airway in both smokers and non-smokers. Although epitheliotropism does not exist in the bronchial tree, gamma delta T-cells seem to form a significant part of the bronchial gland inflammation associated with smoking.

Acute respiratory failure caused by infection of the lungs leading to respiratory failure is termed acute respiratory distress syndrome (ARDS). It includes the recent pandemic, causing coronavirus disease (COVID-19). Higher mortality rates are commonly associated with critical care patients having ARDS. The treatment normally requires the use of mechanical ventilation, which potentially can lead to complications and increased lung injury termed as ventilator-induced lung injury (VILI). It is primarily caused by high inspiratory pressure or cyclical opening during respiration due to cyclic collapse during expiration. Heterogeneous ventilation is documented as the third mechanism responsible for VILI. To enumerate these mechanisms leading to VILI, a digital twin (DT) model was developed and implemented to study the flowrates and the pressure distribution in a simplified symmetric triple bifurcation human tracheobronchial airway model. A flow resistance network was generated using lumped parameter modeling techniques prior to formulating the digital twin. The individual resistance values for each zone in the bifurcating network were computed using flow parameters obtained from computational fluid dynamics (CFD) simulations. Five different inlet flows corresponding to Reynolds numbers (Re) varying from 100 to 2000 were simulated to generate points for the lumped parameter model. The goal of this study was to create a digital twin for the human respiratory system. The aim of this study was to investigate the variety of flow features induced in the airways for optimizing the settings during mechanical ventilation. These investigations focused on the pulmonary vasculature for developing a Lung Physiome. The main objective was to develop a flow-impedance network that was distilled from CFD simulations performed during this study. This was realized by utilizing star-delta network transformation (i.e., using an electrical network analogy), i.e., using a reduced-order model (ROM) based on results obtained from the CFD simulations of specific airway geometries. The proposed methodology was designed to simplify the numerical and computational procedures for obtaining the desired flow parameter predictions for the complex flow fields inside lung airways. These endeavors enabled the development of a simplified digital twin model based on flow resistance network predictions that align with anatomically consistent observations for the human respiratory system. Hence, this study helped demonstrate the feasibility of the development of predictive models that are required for optimizing the operating parameters of mechanical ventilators for individualized therapeutics of patients with ARDS and similar lung diseases (e.g., COVID-19).

Mechanistic modelling in pharmaceutical product and process development: A review of distributed and discrete approaches

Airway remodeling is another important feature of bronchial asthma except for chronic airway inflammation.Study shows that in recent years,Toll-like receptors can regulate a variety of factors such as growth factors,cytokines,inflammatory mediators and so on,which induced airway remodeling production and activation,leading to airway remodeling Ultimately. Key words: Toll-like feceptors; Bronchial asthma; Airway remodeling

In order to deal with modeling problem of a pressure balance system with time-delay, nonlinear, time-varying and uncertain characteristics, an intelligent modeling procedure is proposed, which is based on artificial neural network (ANN) and input-output data of the system during shield tunneling and can overcome the precision problem in mechanistic modeling (MM) approach. The computational results show that the training algorithm with Gauss-Newton optimization has fast convergent speed. The experimental investigation indicates that, compared with mechanistic modeling approach, intelligent modeling procedure can obviously increase the precision in both soil pressure fitting and forecasting period. The effectiveness and accuracy of proposed intelligent modeling procedure are verified in laboratory tests.