Red blood cell distribution in simplified capillary networks

2010 ◽  
Vol 368 (1921) ◽  
pp. 2897-2918 ◽  
Author(s):  
Dominik Obrist ◽  
Bruno Weber ◽  
Alfred Buck ◽  
Patrick Jenny
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Discrete Model ◽  
Self Regulation ◽  
Capillary Network ◽  
Human Organism ◽  
Regulation Mechanism ◽  
Special Role ◽  
Detailed Model ◽  
Capillary Networks

A detailed model of red blood cell (RBC) transport in a capillary network is an indispensable element of a comprehensive model for the supply of the human organism with oxygen and nutrients. In this paper, we introduce a two-phase model for the perfusion of a capillary network. This model accounts for the special role of RBCs, which have a strong influence on network dynamics. Analytical results and numerical simulations with a discrete model and a generic network topology indicate that there exists a local self-regulation mechanism for the flow rates and a global de-mixing process that leads to an inhomogeneous haematocrit distribution. Based on the results from the discrete model, we formulate an efficient algorithm suitable for computing the pressure and flow field as well as a continuous haematocrit distribution in large capillary networks at steady state.

Direct observation of epicardial coronary capillary hemodynamics during reactive hyperemia and during adenosine administration by intravital video microscopy

2005 ◽  
Vol 288 (3) ◽  
pp. H1437-H1443 ◽  
Author(s):  
Takahiko Kiyooka ◽  
Osamu Hiramatsu ◽  
Fumiyuki Shigeto ◽  
Hiroshi Nakamoto ◽  
Hiroyuki Tachibana ◽  
...  
Keyword(s):  
Blood Cell ◽  
Flow Velocity ◽  
Red Blood Cell ◽  
Capillary Flow ◽  
Reactive Hyperemia ◽  
Video Microscopy ◽  
Capillary Network ◽  
Arterial Flow ◽  
Canine Heart ◽  
Adenosine Administration

Using high-resolution intravital charge-coupled device video microscopy, we visualized the epicardial capillary network of the beating canine heart in vivo to elucidate its functional role under control conditions, during reactive hyperemia (RH), and during intracoronary adenosine administration. The pencil-lens video-microscope probe was placed over capillaries fed by the left anterior descending artery in atrioventricular-blocked hearts of open-chest, anesthetized dogs paced at 60–90 beats/min ( n = 17). In individual capillaries under control conditions, red blood cell flow was predominant during systole or diastole, indicating that the watershed between diastolic arterial and systolic venous flows is located within the capillaries. Capillary flow increased during RH and reached a peak flow velocity (2.1 ± 0.6 mm/s), twice as high as control (1.2 ± 0.5 mm/s), with enhancement of intercapillary cross-connection flow and enlargement of diameter (by 17%). With adenosine, capillary flow velocity significantly increased (1.8 ± 0.7 mm/s). However, the increase in volumetric capillary flow with adenosine estimated from red blood cell velocity and diameter was less than the increase in arterial flow, whereas that during RH was nearly equivalent to the increase in arterial flow. There was a time lag of ∼1.5 s for refilling of capillaries during RH, indicating their function as capacitance vessels. In conclusion, the coronary capillary network functions as 1) the major watershed between diastolic-dominant arterial and systolic-dominant venous flows, 2) a capacitor, and 3) a significant local flow amplifier and homogenizer of blood supply during RH, but with adenosine the increase in capillary flow velocity was less than the increase in arterial flow.

A lab-on-a-chip capillary network for red blood cell hydrodynamics

2010 ◽  
Vol 9 (2-3) ◽  
pp. 585-591 ◽  
Author(s):  
Yung-Chou Chen ◽  
Guo-Yang Chen ◽  
Yan-Cheng Lin ◽  
Gou-Jen Wang
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Lab On A Chip ◽  
Capillary Network

The impact of capillary dilation on the distribution of red blood cells in artificial networks

2015 ◽  
Vol 308 (7) ◽  
pp. H733-H742 ◽  
Author(s):  
Franca Schmid ◽  
Johannes Reichold ◽  
Bruno Weber ◽  
Patrick Jenny
Keyword(s):  
Flow Rate ◽  
Self Regulation ◽  
Blood Flow Rate ◽  
Regulation Mechanism ◽  
Parent Vessel ◽  
Capillary Networks ◽  
Dilation Factor ◽  
Network Simulations ◽  
The Impact ◽  
Capillary Dilation

Recent studies suggest that pericytes around capillaries are contractile and able to alter the diameter of capillaries. To investigate the effects of capillary dilation on network dynamics, we performed simulations in artificial capillary networks of different sizes and complexities. The unequal partition of hematocrit at diverging bifurcations was modeled by assuming that each red blood cell (RBC) enters the branch with the faster instantaneous flow. Network simulations with and without RBCs were performed to investigate the effect of local dilations. The results showed that the increase in flow rate due to capillary dilation was less when the effects of RBCs are included. For bifurcations with sufficient RBCs in the parent vessel and nearly equal flows in the branches, the flow rate in the dilated branch did not increase. Instead, a self-regulation of flow was observed due to accumulation of RBCs in the dilated capillary. A parametric study was performed to examine the dependence on initial capillary diameter, dilation factor, and tube hematocrit. Furthermore, the conditions needed for an efficient self-regulation mechanism are discussed. The results support the hypothesis that RBCs play a significant role for the fluid dynamics in capillary networks and that it is crucial to consider the blood flow rate and the distribution of RBCs to understand the supply of oxygen in the vasculature. Furthermore, our results suggest that capillary dilation/constriction offers the potential of being an efficient mechanism to alter the distribution of RBCs locally and hence could be important for the local regulation of oxygen delivery.

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