Effect of erythrocyte aggregation and flow rate on cell-free layer formation in arterioles

Abstract

Formation of a cell-free layer is an important dynamic feature of microcirculatory blood flow, which can be influenced by rheological parameters, such as red blood cell aggregation and flow rate. In this study, we investigate the effect of these two rheological parameters on cell-free layer characteristics in the arterioles (20-60 mum inner diameter). For the first time, we provide here the detailed temporal information of the arteriolar cell-free layer in various rheological conditions to better describe the characteristics of the layer variation. The rat cremaster muscle was used to visualize arteriolar flows, and the extent of aggregation was raised by dextran 500 infusion to levels seen in normal human blood. Our results show that cell-free layer formation in the arterioles is enhanced by a combination of flow reduction and red blood cell aggregation. A positive relation (P < 0.005) was found between mean cell-free layer widths and their corresponding SDs for all conditions. An analysis of the frequency and magnitudes of cell-free layer variation from their mean value revealed that the layer deviated with significantly larger magnitudes into the red blood cell core after flow reduction and dextran infusion (P < 0.05). In accordance, the disparity of cell-free layer width distribution found in opposite radial directions from its mean became greater with aggregation in reduced flow conditions. This study shows that the cell-free layer width in arterioles is dependent on both flow rate and red blood cell aggregability, and that the temporal variations in width are asymmetric with a greater excursion into the red blood cell core than toward the vessel wall.

Velocimetry of red blood cells in microvessels by the dual-slit method: Effect of velocity gradients

“…Moreover, the influence of the bluntness of the RBC velocity profile has also been highlighted (Pittman and Ellsworth, 1986). In spite of these uncertainties, the dual-slit technique for in vitro (Sakai et al, 2009) or in vivo (Ong et al, 2010;Salazar Vazquez et al, 2010;Villela et al, 2009) investigations of blood microcirculation is still of interest in practice. Recently, Sapuppo et al (2007) developed and characterized an improved real-time automated measurement system based on the dual-slit methodology.…”

Two-dimensional transient model for prediction of arteriolar NO/O2 modulation by spatiotemporal variations in cell-free layer width

“…For the in vivo CFL data used in the numerical simulation in this study, we utilized the same experimental procedure as our previous studies on arteriolar blood flow in the rat cremaster muscle (Ong et al, 2010). A detailed description of the experimental setup and animal preparation is available in that report and is briefly summarized here.…”

“…The formation of CFL near the vessel wall results from the axial migration of red blood cells (RBCs) towards the flow center (Goldsmith, 1986;McHedlishvili and Maeda, 2001). Hence, enhanced axial accumulation of the cells by RBC aggregation promotes the prominent formation of CFL adjacent to the endothelium (Maeda, 1996;Ong et al, 2010;Soutani et al, 1995;Tateishi et al, 1994). The CFL between the blood lumen (RBC core) and the endothelium forms a diffusion barrier to O 2 delivery from the blood stream to the tissues as well as to NO scavenging by RBCs (Butler et al, 1998;Lamkin-Kennard et al, 2004b;Vaughn et al, 1998).…”

A Microfluidic-Based Arteriolar Network Model for Biophysical and Bioanalytical Investigations

“…5a) displays a quasi-symmetric and blunt shape, mainly due to the accumulation of blood cells towards the axis of the vessel (axial migration) and the formation of a CDL in the near wall region [13,14,16,17]. Such characteristics of blood velocity profiles in the microvasculature have been widely observed in vivo [54]. Particularly, velocity profile bluntness has been observed to decrease with reducing discharge haematocrit due to the increase of CDL width and the size reduction of the RBC-rich region [55].…”