title: Peculiar flow patterns of RBCs suspended in viscous fluids and perfused through a narrow tube (25 microm).
abstract: 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 microm) 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 ( approximately 8.8 microm). 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.
authors.affiliation: Research Institute for Science and Engineering, Waseda University, Waseda University, Tokyo, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sakai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sato
authors.forename: Naoto
authors.initials: N
authors.lastname: Okuda
authors.forename: Shinji
authors.initials: S
authors.lastname: Takeoka
authors.forename: Nobuji
authors.initials: N
authors.lastname: Maeda
authors.forename: Eishun
authors.initials: E
authors.lastname: Tsuchida
mesh_terms: D001783:Blood Flow Velocity; D003911:Dextrans; D004907:Erythrocyte Deformability / Q000502:physiology*; D004912:Erythrocytes / Q000166:cytology* / Q000502:physiology*; D018056:Hemorheology / Q000502:physiology*; D006801:Humans; D008081:Liposomes; D008833:Microcirculation / Q000502:physiology; D008955:Models, Cardiovascular; D012965:Sodium Chloride; D013314:Stress, Mechanical; D014783:Viscosity
chemical_list: D003911:Dextrans; D008081:Liposomes; D012965:Sodium Chloride