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BACKGROUND   Of the many possible factors that may contribute to orthostatic intolerance, the loss of circulating blood because of capillary filtration is one of the few that can explain the gradual decline of arterial pressure during stand tests. This study used a computer model to investigate the relative importance of haemodynamic parameters, including(More)
Hemolysis in clinical blood samples leads to inaccurate assay results and often to the need for repeated blood draws. In vitro experiments were conducted to determine the influence on hemolysis in phlebotomy needles and catheters of pressure difference, cannula diameter, and cannula material. Fresh blood from five human volunteers was forced from a syringe(More)
A numerical model of the cardiovascular system was used to quantify the influences on cardiac function of intrathoracic pressure and intravascular and intraventricular hydrostatic pressure, which are fundamental biomechanical stimuli for orthostatic response. The model included a detailed arterial circulation with lumped parameter models of the atria,(More)
Motivated by the lateral migration phenomena of fresh and glutaraldehyde-fixed red blood cells in a field flow fractionation (FFF) separation system, we studied the transverse hydrodynamic lift on a slightly flexible cylinder in a two-dimensional channel flow. The finite element method was used to analyze the flow field with the cylinder at different(More)
Hemolysis is caused by fluid stresses in flows within hypodermic needles, blood pumps, artificial hearts, and other cardiovascular devices. Developers of cardiovascular devices may expend considerable time and effort in testing of prototypes, because there is currently insufficient understanding of how flow-induced cell damage occurs to accurately predict(More)
An analytical solution for pulsatile flow of a generalized Maxwell fluid in straight rigid tubes, with and without axial vessel motion, has been used to calculate the effect of blood viscoelasticity on velocity profiles and shear stress in flows representative of those in the large arteries. Measured bulk flow rate Q waveforms were used as starting points(More)
Alzheimer’s disease is characterized by accumulation of amyloid-β (Aβ) in the brain and in the walls of cerebral arteries. The focus of this work is on clearance of Aβ along artery walls, the failure of which may explain the accumulation of Aβ in Alzheimer’s disease. Periarterial basement membranes form continuous channels from cerebral capillaries to major(More)
PURPOSE To validate conventional phase-contrast MRI (PC-MRI) measurements of steady and pulsatile flows through stenotic phantoms with various degrees of narrowing at Reynolds numbers mimicking flows in the human iliac artery using stereoscopic particle image velocimetry (SPIV) as gold standard. MATERIALS AND METHODS A series of detailed experiments are(More)
A significant fraction of astronauts experience postflight orthostatic intolerance (POI) during 10-min stand tests conducted on landing day. The average time that nonfinishers can stand is about 7 min. This phenomenon, including the delay in occurrence of presyncope, was studied with a five-compartment model of the cardiovascular system incorporating(More)
One proposed method to overcome postflight orthostatic intolerance is for astronauts to undergo inflight centrifugation. Cardiovascular responses were compared between centrifuge and gravitational conditions using a seven-compartment cardiovascular model. Vascular resistance, heart rate, and stroke volume values were adopted from literature, while(More)