Browsing by Author "Trinkmann, Frederik"

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    Investigation of inert gas washout methods in a new numerical model based on an electrical analogy
    (2024) Schmidt, Christoph; Hatziklitiu, Wasilios; Trinkmann, Frederik; Cattaneo, Giorgio; Port, Johannes
    AbstractInert gas washout methods have been shown to detect pathological changes in the small airways that occur in the early stages of obstructive lung diseases such as asthma and COPD. Numerical lung models support the analysis of characteristic washout curves, but are limited in their ability to simulate the complexity of lung anatomy over an appropriate time period. Therefore, the interpretation of patient-specific washout data remains a challenge. A new numerical lung model is presented in which electrical components describe the anatomical and physiological characteristics of the lung as well as gas-specific properties. To verify that the model is able to reproduce characteristic washout curves, the phase 3 slopes (S3) of helium washouts are simulated using simple asymmetric lung anatomies consisting of two parallel connected lung units with volume ratios of 1.250.75, 1.500.50, and 1.750.25 and a total volume flow of 250 ml/s which are evaluated for asymmetries in both the convection- and diffusion-dominated zone of the lung. The results show that the model is able to reproduce the S3 for helium and thus the processes underlying the washout methods, so that electrical components can be used to model these methods. This approach could form the basis of a hardware-based real-time simulator.Graphical abstract
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    Investigation of tracer gas transport in a new numerical model of lung acini
    (2022) Schmidt, Christoph; Joppek, Christoph; Trinkmann, Frederik; Takors, Ralf; Cattaneo, Giorgio; Port, Johannes
    Obstructive pulmonary diseases are associated with considerable morbidity. For an early diagnosis of these diseases, inert gas washouts can potentially be used. However, the complex interaction between lung anatomy and gas transport mechanisms complicates data analysis. In order to investigate this interaction, a numerical model, based on the finite difference method, consisting of two lung units connected in parallel, was developed to simulate the tracer gas transport within the human acinus. Firstly, the geometries of the units were varied and the diffusion coefficients ( D ) were kept constant. Secondly, D was changed and the geometry was kept constant. Furthermore, simple monoexponential growth functions were applied to evaluate the simulated data. In 109 of the 112 analyzed curves, monoexponential function matched simulated data with an accuracy of over 90%, potentially representing a suitable numerical tool to predict transport processes in further model extensions. For total flows greater than 5 × 10 -4  ml/s, the exponential growth constants increased linearly with linear increasing flow to an accuracy of over 95%. The slopes of these linear trend lines of 1.23 µl -1 ( D  = 0.6 cm 2 /s), 1.69 µl -1 ( D  = 0.3 cm 2 /s), and 2.25 µl -1 ( D  = 0.1 cm 2 /s) indicated that gases with low D are more sensitive to changes in flows than gases with high D .