Damped Oscillation Rheometer Research Articles

Heterogeneous phase fibrinolysis rates by damped oscillation rheometry.

Devices gauging viscoelastic properties of blood during coagulation like the thromboelastograph support fundamental research as well as point of care needs. Associated fibrinolysis data are based on endogenous species or plasminogen activator added to a homogeneous sample prior to clot formation. Digestion in a monolithic structure differs from the physical situation of thrombolytic therapy where surface reactions dominate. This study aims to develop rheological testing for heterogeneous phase fibrinolysis. Fibrinolysis rates were determined by phase change of a solid clot induced by autologous plasma/streptokinase (SK) in a rheometer sensitive to viscous damping. Initial slope or overall change in the logarithmic damping factor indicated fibrinolytic rates. Rates depended on clot geometry, phase volumes, clot composition and SK concentration. The damped oscillation rheometer can be adapted to determine relative rates of heterogeneous fibrinolysis in vitro.

Change of the initiation time of blood coagulation in pregnancy from 10-months to postpartum

We measured the time of initiation of blood coagulation (Ti) from pregnancy 10-months (36~40 weeks) till 1-month after delivery, paying particular attention to the very early postpartum period, using a damped oscillation rheometer that is approximately 160 times more sensitive than the Thromboelastogram® to evaluate the risk of thrombus formation. Blood samples were obtained from healthy volunteers at pregnancy 10-month, 1-hour, 3-hours, 4-days, 7-days, 3-weeks and 1-month after delivery. Ti values at pregnancy 10-month, 1-hour, 3-hours, 4-days, 7-days, 3-weeks, 1-month after delivery and in non-pregnant females were 20.4 ± 2.2, 11.7 ± 1.6, 13.2 ± 3.1, 17.2 ± 2.0, 20.2 ± 1.6, 21.4 ± 4.0, 24.6 ± 3.6, and (25.0 ± 3.4) minutes, respectively. Ti was significantly shorter at pregnancy 10-month, 1-hour, 3-ours, 4-days, 7-days and 3-weeks after delivery than in non-pregnant females. These data show that the blood of pregnant females is more hypercoagulable than non-pregnant females from pregnancy 10-month until 3-weeks post delivery, suggesting that they are at high risk of VTE after discharge from hospital.

Simultaneous measurement of blood coagulation and erythrocyte sedimentation by means of a rheological technique

With a damped-oscillation rheometer, changes in the rheological properties, i.e., logarithmic damping factor (LDF) and period, as obtained from a damped-oscillation curve, were monitored during the coagulation of blood. In our earlier studies, the time of onset of coagulation (Ti) of the blood sample was only determined from the change in LDF. When coagulation of the blood and sedimentation of erythrocytes occurred together, the Ti value could not be determined from the change in LDF. In this paper, a method for determining the Ti value from the change in the period of the damped-oscillation curve was investigated. It was found that the period increased and leveled off as blood coagulation progressed, and the Ti value was determined from the middle point between the minimum and maximum values of the period. In addition, it was suggested that the level of erythrocyte sedimentation could be estimated from the initial decrease in LDF. In blood obtained from diabetic patients, a good correlation between the initial decrease in the LDF and the concentration of fibrinogen was observed. Our study demonstrates that when erythrocyte sedimentation and blood coagulation occur simultaneously, this rheological technique makes it possible to measure the Ti value and erythrocyte sedimentation.

Study on early prediction of ovarian hyperstimulation syndrome during hMG-hCG treatment using a damped oscillation rheometer

Objective: It is well known that ovarian hyperstimulation syndrome (OHSS) is a common but sometimes serious side effect during hMG-hCG treatment. Present study was performed to elucidate whether OHSS was predictable during hMG administration by precise measurement of the early stage of the blood coagulation using a damped oscillation rheometer (DOR).

Antithrombogenicity of cultured endothelial cell-detached surface

To examine the antithrombogenicity of cultured endothelial cell-detached surface, a simple hybrid vascular model tube consisting of a glass tube and endothelial cells was constructed. To detach the endothelial cells from the inner surface of the model tube, a steady shear stress of 2 or 8 N m −2 was imposed onto the surface of endothelial cell monolayer by means of a coaxial double cylinder rotational-type apparatus. Coagulation of blood in contact with the endothelial cell-detached surface was examined using a damped oscillation rheometer. Coagulation of whole blood in the cell-detached tube occurred at about 40 min, which was almost the same as that in the endothelial cell-coated tube. A few platelets without shape change adhered to the endothelial cell-detached surface. These data suggest that the endothelial cell-detached surface may exhibit antithrombogenic and anticoagulant surfaces. Biochemical analyses showed that the glass surface, where endothelial cell was detached, was covered with components such as collagen type IV that is considered to be produced from the endothelial cells on the glass surface.

Anemia as a risk factor of hemorrhagic tendency during surgery.

Although it is well-known that a hemorrhagic tendency in patients with massive bleeding during surgery, or with anemia before surgery, is difficult to control, its mechanism is still obscure. Using a damped oscillation rheometer, we measured the initiation time (Ti) of whole blood with several concentrations of red blood cells (RBCs) and the Ti of platelet-free plasma (PFP) with various concentrations of RBCs. The Ti of the whole blood became prolonged according to the dilution of the RBC concentration. RBCs could coagulate the PFP, and the Ti of PFP also was prolonged according to the dilution of the RBC concentration. These results suggest that RBCs might have an important role as a phospholipid supplier in the intrinsic pathway of the blood-coagulation mechanism. Anemia could thus represent a risk factor for hemorrhagic tendency during surgery due to lower RBC concentrations.

F308. Rheological measurement of blood coagulation in normal and pre-eclamptic pregnancies using a damped oscillation rheometer

F308. Rheological measurement of blood coagulation in normal and pre-eclamptic pregnancies using a damped oscillation rheometer

S18.3. Adaptation of a damped oscillation rheometer to the in vitro study of thrombolysis

S18.3. Adaptation of a damped oscillation rheometer to the in vitro study of thrombolysis

Application of a Damped Oscillation Rheometer to Observe Sol-Gel Transition in a Food System.

A damped oscillation rheometer was used to observe the gelation process of soy proteins. A small amount (∼1 cm3) of sample sol in a capped container was subjected to repeated rotational oscillations at a high temperature. The logarithmic damping factor (LDF) and the period of the oscillations were derived from the damped oscillation curve. Since the LDF value first increased and then decreased during the gelation, the increase in LDF was a good indication of the initiation of the sol-gel transition.

Measurement of blood coagulation by a damped oscillation rheometer

Measurement of blood coagulation by a damped oscillation rheometer

Viscoelasticity of fibrinogen solution and of blood during coagulation studied by a new damped oscillation rheometer.

The behavior of a newly developed damped oscillation type rheometer was analyzed for fibrinogen solution and blood during coagulation. This rheometer consists of a cylindrical tube suspended from a torsion wire, that is filled with liquid to be tested. The logarithmic damping factor (LDF) during coagulation for blood and fibrinogen solution was obtained by this rheometer, which was closely related to the changes of viscosity and/or viscoelasticity of the blood sample. The slight increase of LDF prior to the rapid decrease was observed for blood. The increase of LDF would be reflected in the formation of the aggregation structure of red blood cells (rouleaux network) prior to the formation of fibrin network. The value of LDF for fibrinogen solution sharply increased and then decreased through a maximum value with the progress of coagulation, although the change of LDF was remarkably dependent on the fibrinogen concentration. The initial increase in LDF for fibrinogen solution was considered to be due to the formation of small clots in the solution. The decrease in LDF after attaining a maximum value is ascribed to the formation of fully developed fibrin network. The maximum value of LDF during coagulation for fibrinogen solution is higher than that for blood. The behavior was compared with that for non-biological fluids such as viscosity standard liquids and polyvinyl alcohol solution. From those data, it was concluded that the higher value of LDF than that for Newtonian liquids was due to the formation of aggregation structure or inhomogeneous fine clots in the liquid, which was accompanied with the appearance of the elasticity.

A Newly Developed Damped Oscillation Type Rheometer

A new type of damped oscillation rheometer was developed for the study of biorheology. The rheometer consists of the cylindrical tube suspended from a torsion wire and filled with test liquid. The cylindrical tube may be made of various materials. The tube is excited in torsional oscillation and the subsequent damped oscillation is observed. The apparatus can sensitively follow the change of fluidity of liquid sample. Changes of logarithmic damping factor for blood and fibrinogen solution during coagulation were measured. The change of logarithmic damping factor for blood during coagulation remarkably depended on tube material, suggesting that the present method is probably available for in vitro evaluation of anticoagulability of artificial materials as well as for analysis of coagulation mechanism of blood.

A Newly Developed Damped Oscillation Type Rheometer

Theoretical basis for a newly developed damped oscillation rheometer is presented for a Newtonian fluid. This rheometer essentially consists of a cylindrical tube suspended by a torsion wire and filled with fluid to be tested. The damped oscillation of the cylinder is observed. Based on some assumptions, the equations of motion for a Newtonian fluid in the tube are solved. The numerical solution and some approximate solutions valid for certain ranges of parameters are obtained. From these solutions the logarithmic damping factor and the period of oscillation are obtained as functions of fluid viscosity.