1. Ktisis Cyprus University of Technology

The fluidity of blood at different levels of oxygen level

View Statistics Email Alert RSS Feed

Primary Data

Project title
The fluidity of blood at different levels of oxygen level
Code
HEMODEL2
Project Coordinator
Start date
01-04-2012
Expected Completion
31-03-2014
 

Description

Abstract
Ischemia-reperfusion injury is common clinical condition of various cardiovascular diseases, in particular, acute myocardial infarction. One of the characteristics is low blood oxygen content (hypoxia) during ischemia, followed by immediate reoxygenation after clinical restoration of blood flow, and even more by increased oxidative stress as a result of reactive oxygen species (ROS) production in damaged cells and neutrophills. It is important to elucidate if hypoxia-reoxygenation injuries causes changes in erythrocyte deformability and aggregation. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise. Generalized hypoxia occurs in healthy people at high altitude, which can lead to pulmonary or cerebral edema which are potentially fatal. Hypoxia also occurs in healthy individuals when breathing mixtures of gases with low oxygen content, e.g. while diving underwater. The rheological properties of blood depend on oxygen concentration. Thus, studying the hemorheology and hemodynamics at different blood oxygen concentrations could gain important insight into the (patho-) physiological regulation of blood flow at the erythrocyte level. The Slovenian partners will examine the influence of oxygen concentration level in whole human blood on its rheological properties. Whole human blood will be taken from different healthy donors having different hematocrit, ranging from 0,3 to 0,5. Samples with different oxygen level will be prepared by using perfusion cell equipped with gas supply to drive out the oxygen (by nitrogen), or to fully saturate blood with oxygen. The rheological properties will be measured in the 4Β°C to 37Β°C temperature range using a rotational controlled stress rheometer. Based on our previous experimental results the Herschel-Bulkley non-Newtonian rheological model will be used to simulate blood behavior under shear. The goal of the project is to determine the rheological properties of blood at the aforementioned oxygenation states using the appropriate rheological model and investigate its flow behavior in arteries. The material parameters in the rheological model and their temperature and hematocrit dependence will be determined based on experimental data. The Cypriot partners will investigate the use of proper constitutive equations for whole human blood with different oxygen concentrations. The Herschel-Bulkley and other non-Newtonian model describing both shear thinning and yield stress will be employed and the temperature and hematocrit dependence of all material parameters will be studied. All models will be tested in model 2D and realistic geometries, the latter produced from 3D-rigid wall reconstructions of available MRI images of the right carotid bifurcation obtained in vivo from healthy volunteers. The constitutive equations for blood will be regularized using the Papanastasiou model and its counterparts in each case. A commercial code as well as existing in-house finite-element software will then be used with realistic three-dimensional meshes of coronary arteries and other blood vessels aiming at providing useful information for vascular surgery and heart valve testing.
 
Keyword(s)
Ischemia-reperfusion injury
Cardiovascular disease
Acute myocardial infarction
Rheological model