Complex Vascular Networks

Complex network topologies are a hallmark of many organs. Often, the particular topologies lead to dynamical phenomena which are important to the physiological function of an organ (e.g. the Windkessel effect in the arterial tree) or which are a central element of a certain pathology (e.g. congenital vascular malformations).

Our interest includes vascular networks at different scales (e.g. capillary networks of the cerebralcirculation) and also extends beyond the cardiovascular system, e.g. to the airway tree in the respiratory system. Out research typically concentrates on the study of the transport of substances through the network by advective and diffusive processes. In many cases, this transport leads to heterogeneous distributions of substances prompting specific physiological reactions. We study such dynamical phenomena with the help of custom-tailored computer models and with in vitro experiments. Wherever possible we collaborate with other research groups to obtain complementary data from in vivo experiments.

Blood rheology in cerebral microcirculation

The distribution of red blood cells (RBCs) in the cerebral microcirculation is critical for the brain oxygenation, metabolism and it is involved in many brain disorders (e.g. Alzheimer, ischemic stroke). Transient changes of local RBCs concentration have a strong impact on the local flow resistance with effects on the flow and pressure fields in the whole network. Our research aims at investigating the distribution of RBCs at the capillary level i.e. focusing on the separation of cells and plasma at consecutive microvascular bifurcations. Different approaches are being explored for modelling cerebral blood flow: i) in vitro modelling, using microfluidics ii) in vivo measurements of RBCs velocities at capillary bifurcations (in collaboration with the Institute of Pharmacology and Toxicology, University of Zurich) and iii) in silico modelling (in collaboration with the Institute of Fluid Dynamics, ETH Zurich).

Arterio-venous malformations

Vascular malformations are localized defects in vascular morphogenesis. Typically, the lesions are composed of an irregular network of anomalous blood vessels. The appropriate treatment strategy depends strongly on the hemodynamic characteristics of the vascular network. Therefore, we are developing a computational tool that allows the clinical practitioner to simulate the blood flow and sclerosant transport within the patient-specific malformation geometry. This will allow predicting the outcome of different treatment strategies and thus reduce the number of treatment sessions and minimize the risks associated with each intervention.

 

Contact: Sabrina Frey, MSc

Fractal lung

Fractal lung is a numerical model to simulate gas transport in an asymmetric network. The model morphology is based on a bifurcation scheme approximating the fractal geometry of airways in the human lung. The goal of the project is the development of a tool to simulate so called washout tests helping Pneumologists analyzing the profiles that are obtained from measuring a tracer gas concentration at the mouth. Multi or single-breath washout test are performed to monitor lung disease progression and treatment effects.

 

Contact: David Hasler, MSc