Measurement of Individual Red Blood Cell Motions Under High Hematocrit Conditions Using a Confocal Micro-PTV System

Abstract

Developments in optical experimental techniques have helped in elucidating how blood flows through microvessels. Although initial developments were encouraging, studies on the flow properties of blood in microcirculation have been limited by several technical factors, such as poor spatial resolution and difficulty obtaining quantitative detailed measurements at such small scales. Recent advances in computing, microscopy, and digital image processing techniques have made it possible to combine a particle tracking velocimetry (PTV) system with a confocal microscope. We document the development of a confocal micro-PTV measurement system for capturing the dynamic flow behavior of red blood cells (RBCs) in concentrated suspensions. Measurements were performed at several depths through 100-µm glass capillaries. The confocal micro-PTV system was able to detect both translational and rotational motions of individual RBCs flowing in concentrated suspensions. Our results provide evidence that RBCs in dilute suspensions (3% hematocrit) tended to follow approximately linear trajectories, whereas RBCs in concentrated suspensions (20% hematocrit) exhibited transversal displacements of about 2% from the original path. Direct and quantitative measurements indicated that the plasma layer appeared to enhance the fluctuations in RBC trajectories owing to decreased obstruction in transversal movements caused by other RBCs. Using optical sectioning and subsequent image contrast and resolution enhancement, the system provides previously unobtainable information on the motion of RBCs, including the trajectories of two or more RBCs interacting in the same focal plane and RBC dispersion coefficients in different focal planes.

Human red blood cell behavior under homogeneous extensional flow in a hyperbolic-shaped microchannel

“…[29][30][31] Sample cells were selected at various positions in the y-axis in the upstream region of the microchannel to obtain a representative illustration of the trajectories as shown in Figure 5. We should note that the same cell cannot be tracked all the way from upstream to downstream of the contraction region, and Figure 5 is a combination of three separate sets of images corresponding to different axial regions.…”

A microfluidic device for partial cell separation and deformability assessment

“…These phenomena include plasma skimming [1], cell-free layer (CFL) [2,3,4], leukocyte margination [5] and bifurcation law [6]. Recently, several researchers have used these effects and replicated in microfluidic systems.…”

“…Recently, several researchers have used these effects and replicated in microfluidic systems. In microchannels RBCs, due to their deformability and lift forces, tend to be concentrated around the center of the microchannels while white blood cells (WBCs) and rigid RBCs (such as Malaria RBCs) tend to migrate to the CFL originated at regions close to the walls [1][2][3][4][5]. Bifurcation law [6] states that RBCs behavior, in microchannels with bifurcations, tends to be oriented to the wide microchannel.…”

Red Blood Cells Motion in a Glass Microchannel

“…As a consequence, many rheological studies have been performed on both microvessels and microchannels to investigate the effect of the hematocrit (Hct), geometry, and temperature on the RBCs flowing behavior [2,3,10]. Recently Lima and his colleagues measured the red blood cells (RBCs) radial dispersion (Dyy) in both glass [6,7] and polydimensiloxane (PDMS) [8] microchannels by using a confocal micro-PTV system. By comparing Lima et al results with the measurements performed by Goldsmith and his colleagues [3] several quantitative deviations were observed between both experimental results.…”