Biomedical subjects

Sehyun Shin

Publications and source records attributed to Sehyun Shin.

6 recordsLinked to original sources

PubMed2005

Rapid cell-deformability sensing system based on slit-flow laser diffractometry with decreasing pressure differential.

A slit-flow apparatus with a laser-diffraction method has been developed with significant advances in ektacytometry design, operation and data analysis. In the slit-flow ektacytometry, the deformation of red blood cells subjected to continuously decreasing shear stress in slit-flow can be quickly measured with adopting a laser-diffraction technique. Both the laser-diffraction image and pressure were measured with respect to time, which enable to determine the elongation index (EI) and the shear stress. The range of shear stress is 0-35 Pa and the measuring time is < 2 min. The EI is determined from an isointensity curve in the diffraction pattern using an ellipse-fitting program. The present study proposed the deformability index (DI) as a new measure of the RBC deformability, which is defined as an integral area under the EI curve between 0 and tau10 (tau(w) = 0-10). The key advantage of this design is the incorporation of a disposable element that holds the blood sample, which enables the present system to be easily used in a clinical setting.

Biosensing Techniques↗

PubMed2005

Slit-flow ektacytometry: laser diffraction in a slit rheometer.

BACKGROUND: Deformability of red blood cells (RBCs) is a determinant of blood flow resistance as RBCs pass through small capillaries of the microcirculation. Available techniques for measuring RBC deformability often require a washing process after each measurement, which is not optimal for day-to-day clinical use. METHODS: A laser diffraction technique has been combined with slit-flow rheometry, which shows significant advances in ektacytometric design, operation, and data analysis. The essential features of this design are its simplicity (ease of operation and no moving parts) and a disposable element that is in contact with the blood sample. RESULTS: With slit ektacytometry, the deformation of RBCs subjected to continuously decreasing shear stress in a slit flow can be quickly measured with extremely small quantities of blood. The measurements with the slit ektacytometer were compared with those of LORCA and a strong correlation was apparent. The deformability of the hardened RBCs was markedly lower than that of the normal RBCs. In addition, the young cells showed higher values of the elongation index than did the old cells. CONCLUSIONS: The newly developed slit ektacytometer can measure RBC deformability with ease and accuracy. In addition, the slit ektacytometer can be easily used in a clinical setting owing to the incorporation of a disposable element that holds the blood sample.

Adult↗

PubMed2004

Blood flow resistance with vibration and its effect on blood cell migration.

The present study investigated the effect of transverse vibration on the hemo-rheological characteristics of blood flow using a newly designed pressure-scanning capillary viscometer. As a transverse vibration was applied, aggregated blood cells become disaggregated. Frequency of vibration was found to be the main parameter causing hemo-rheological changes. For RBC suspension in a non-aggregating medium (Dextran 40), increasing frequency of vibration caused decreased flow resistance. Meanwhile, flow resistance for whole blood increased with frequency of vibration. These seemingly contradictory results could be interpreted without conflict when a comprehensive mechanism of cell migration under vibration is elucidated. The present study confirmed that vibration diminishes RBC aggregation, which triggers two different cell migration mechanisms and subsequently resulted in either increasing or decreasing the flow resistance.

Blood Flow Velocity↗

PubMed2004

Measurement of blood viscosity using a pressure-scanning capillary viscometer.

A newly designed pressure-scanning capillary viscometer is extended to measure the viscosity of whole blood over a range of shear rates without the use of anticoagulants in a clinical setting. In the present study, a single measurement of pressure variation with time replaces the flow rate and pressure drop measurements that are usually required for the operation of a capillary tube viscometer. Using a pressure transducer and capillary, we measured the variation of pressure flowing through capillary tube with respect to time, p(t), from which viscosity and the shear rate were mathematically calculated. For water and anticoagulant-added bloods, there was an excellent agreement found between the results from the pressure scanning capillary viscometer and those from a commercially available rotating viscometer. Also, the pressure-scanning capillary viscometer measured the viscosity of whole blood without heparin or EDTA. This new method overcomes the drawbacks of conventional viscometers in the measurement of whole blood viscosity. First, the pressure-scanning capillary viscometer can accurately and consistently measure the whole blood viscosity over a range of shear rates in less than 2 min without any anticoagulants. Second, this design provides simplicity (i.e., ease of operation, no moving parts, and disposable) and low cost.

Blood Viscosity↗

PubMed2003

Characteristics of blood flow resistance under transverse vibration: red blood cell suspension in Dextran-40.

Vibration under shear flow causes the reduction of flow resistance for shear-thinning fluids. The present study investigates the effect of vibration on the flow resistance of a nonaggregating red blood cell (RBC) suspension with a newly designed pressure-scanning capillary viscometer (PSCV). The PSCV was originally designed to measure non-Newtonian viscosity continuously over a range of shear rates at a time, which was slightly modified and used for the present study. Low-frequency vibration was applied perpendicular to the direction of the flow. The effect of the transverse vibration was investigated for both Newtonian fluids and nonaggregating RBC suspensions. The experimental results showed that the vibration had no effect on the flow resistance of the Newtonian fluids. However, the vibration caused a reduction of the flow resistance of the RBC suspension. The reduction of the flow resistance was strongly dependent on both frequency and amplitude of vibration.

Blood Flow Velocity↗

PubMed2002

Measurement of blood viscosity using mass-detecting sensor.

A newly designed mass-detecting capillary viscometer is extended to measure the viscosity of whole blood over a range of shear rates without the use of anticoagulants in a clinical setting. In the present study as proof of principle, a single measurement of liquid-mass variation with time replaces the flow rate and pressure drop measurements that are usually required for the operation of a capillary tube viscometer. Using a load cell and capillary, we measured the change of mass flowing through capillary tube with respect to the time, m(t), from which viscosity and shear rate were mathematically calculated. For water and adulterated bloods, excellent agreement was found between the results from the mass-detecting capillary viscometer and those from a commercially available rotating viscometer. Also, the mass-detecting capillary viscometer measured the viscosity of unadulterated whole blood without heparin or EDTA. This new method overcomes the drawbacks of conventional viscometers in the measurement of the whole blood viscosity. First, the mass-detecting capillary viscometer can accurately and consistently measure the unadulterated blood viscosity over a range of shear rates in less than 2 min without any anticoagulants. Second, this design provides simplicity (i.e. ease of operation, no moving parts, and disposable) and low cost.

Anticoagulants↗