Peculiar flow patterns of RBCs suspended in viscous fluids and perfused through a narrow tube (25 {micro}m)

• Published in: American journal of physiology. Heart and circulatory physiology 2009-08, Vol.297 (2), p.H583-H589
• Main Authors: Sakai, Hiromi, Sato, Atsushi, Okuda, Naoto, Takeoka, Shinji, Maeda, Nobuji, Tsuchida, Eishun
• Format: Article
• Language: English
• Subjects: Blood Flow Velocity; Cell adhesion & migration; Cells; Coronary vessels; Dextrans; Erythrocyte Deformability - physiology; Erythrocytes; Erythrocytes - cytology; Erythrocytes - physiology; Heart; Hemorheology - physiology; Humans; Liposomes; Microcirculation - physiology; Models, Cardiovascular; Sodium Chloride; Stress, Mechanical; Viscosity
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00352.2009

1 Research Institute for Science and Engineering, Waseda University, and 2 Department of Life Science and Medical Bioscience, Graduate School of Science and Engineering, Waseda University, Tokyo; and 3 Department of Physiology, School of Medicine, Ehime University, Ehime, Japan Submitted 10 April 2009 ; accepted in final form 5 June 2009 Red blood cells (RBCs) generally deform to adopt a parachute-like, torpedo-like, or other configuration to align and flow through a capillary that is narrower than their major axis. As described herein, even in a narrow tube (25 µm) with diameter much larger than that of a capillary, flowing RBCs at 1 mm/s align axially and deform to a paraboloid shape in a viscous Newtonian fluid (505 kDa dextran medium) with viscosity of 23.4–57.1 mPa·s. A high-speed digital camera image showed that the silhouette of the tip of RBCs fits a parabola, unlike the shape of RBCs in capillaries, because of the longer distance of the RBC-free layer between the tube wall and the RBC surface ( 8.8 µm). However, when RBCs are suspended in a "non-Newtonian" viscous fluid (liposome-40 kDa dextran medium) with a shear-thinning profile, they migrate toward the tube wall to avoid the axial lining, as "near-wall-excess," which is usually observed for platelets. This migration results from the presence of flocculated liposomes at the tube center. In contrast, such near-wall excess was not observed when RBCs were suspended in a nearly Newtonian liposome-albumin medium. Such unusual flow patterns of RBCs would be explainable by the principle; a larger particle tends to flow near the centerline, and a small one tends to go to the wall to flow with least resistance. However, we visualized for the first time the complete axial aligning and near-wall excess of RBCs in the noncapillary size tube in some extreme conditions. hemorheology; erythrocytes; viscometry; artificial red cells; microcirculation Address for reprint requests and other correspondence: H. Sakai, Research Institute for Science and Engineering, Waseda Univ., 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan (e-mail: hiromi{at}waseda.jp )