Hemodynamic Analysis of Coronary Artery Microcirculation Using a Pig

Sehyun Shin,Jungsu Park 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.6

Stenosed coronary artery may play an Important role in various coronary heart diseases. However, it has not been known how much stenosed coronary artery affects coronary circulation system, quantitatively. The present study developed a mathematical model for microcirculation in the left common coronary artery (LCCA) with adopting a previously measured morphological data and mechanical properties of the coronary vessels. We examine the effect of percent diameter stenosis on blood flow rate and shear stress for two cases. Case I comprised of one-stenosed element at 10^(th) order (% diameter stenosis are 10, 30, and 50, respectively) Case Ⅱ consisted of completely occluded element at 10^(th) order (number of occluded elements are 0, 1, and 2 out of 8, respectively). As the level of stenosis becomes severe, the shear stress Increases significantly but the flow rate reduction was relatively small. However, for the occluded case, there was linearly proportional reduction of flow rate according to number of occluded elements. Either such high shear stress associated with coronary artery stenosis or reduced flow rate due to occlusion may cause atherosclerosis and myocardial ischemia.

The Effect of Vibration on the Hemorheologicai Characteristics of Non-aggregated Blood

Sehyun Shin,Yun-Hee Ku,Su-Yeon Moon,Jang-Soo Suh 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.7

The present study investigates the hemorheological characteristics of blood flow with applying vibration to a non-aggregating red blood cell suspension. In order to obtain the non-aggre-gating RBC suspension, blood samples were treated with vibration at a specified condition, which viscosities were taken before and after the treatment, respectively. The viscosity of the blood samples after treatment was higher than before treatment. These treated blood samples were forced to flow through a capillary tube that was vibrated perpendicularly to the direction of the flow. The experimental results showed that vibration caused a reduction of the flow resistance of the non-aggregated blood. The reduction of the flow resistance was strongly dependent on both frequency and amplitude of vibration. These results show potential in treating various diseases in the microcirculation associated with blood cell aggregation.

Development of Precision medicine technology with biofluid biopsy

Sehyun Shin(신세현) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.8

Hemorheology and clinical application : association of impairment of red blood cell deformability with diabetic nephropathy

Sehyun Shin,구윤희 한국유변학회 2005 Korea-Australia rheology journal Vol.17 No.3

Background: Reduced deformability of red blood cells (RBCs) may play an important role on the pathogenesis of chronic vascular complications of diabetes mellitus. However, available techniques for measuring RBC deformability often require washing process after each measurement, which is not optimal for day-to-day clinical use at point of care. The objectives of the present study are to develop a device and to delineate the correlation of impaired RBC deformability with diabetic nephropathy. Methods: We developed a disposable ektacytometry to measure RBC deformability, which adopted a laser diffraction technique and slit rheometry. The essential features of this design are its simplicity (ease of operation and no moving parts) and a disposable element which is in contact with the blood sample. We studied adult diabetic patients divided into three groups according to diabetic complications. Group I comprised 57 diabetic patients with normal renal function. Group II comprised 26 diabetic patients with chronic renal failure (CRF). Group III consisted of 30 diabetic subjects with end-stage renal disease (ESRD) on hemodialysis. According to the renal function for the diabetic groups, matched non-diabetic groups were served as control. Results: We found substantially impaired red blood cell deformability in those with normal renal function (group I) compared to non-diabetic control (P = 0.0005). As renal function decreases, an increased impairment in RBC deformability was found. Diabetic patients with chronic renal failure (group II) when compared to non-diabetic controls (CRF) had an apparently greater impairment in RBC deformability (P = 0.07). The non-diabetic cohort (CRF), on the other hand, manifested significant impairment in red blood cell deformability compared to healthy control (P = 0.0001). Conclusions: The newly developed slit ektacytometer can measure the RBC deformability with ease and accuracy. In addition, progressive impairment in cell deformability is associated with renal function loss in all patients regardless of the presence or absence of diabetes. In diabetic patients, early impairment in RBC deformability appears in patients with normal renal function.

Optical Detection of Red Blood Cell Aggregation in a Disposable Microfluidic Channel

Shin Sehyun,Jang Ju-Hee,Park Myung-Soo,Ku Yunhee,Suh Jang-Soo The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.3

The aggregability of red blood cells (RBCs) was determined by laser backscattering light analysis in a microfluidic channel. Available techniques for RBC aggregation often adopt a rotational Couette-flow using a bob-and-cup system for disaggregating RBCs, which causes the system to be complex and expensive. A disposable microfluidic channel and vibration generating mechanism were used in the proposed new detection system for RBC aggregation. Prior to measurement, RBC aggregates in a blood sample were completely disaggregated by the application of vibration-induced shear. With the present apparatus, the aggregation indexes of RBCs can be measured easily with small quantities of a blood sample. The measurements with the present aggregometer were compared with those of LORCA and the results showed a strong correlation between them. The aggregability of the defibrinogenated blood RBCs is markedly lower than that of the normal RBCs. The noble feature of this design is the vibration-induced disaggregation mechanism, which can incorporate the disposable element that holds the blood sample.

Hemodynamic Analysis of Coronary Artery Microcirculation Using a Pig's Morphometric Data

Shin Sehyun,Park Jungsu The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.6

Stenosed coronary artery may play an important role in various coronary heart diseases. However, it has not been known how much stenosed coronary artery affects coronary circulation system, quantitatively. The present study developed a mathematical model for microcirculation in the left common coronary artery (LCCA) with adopting a previously measured morphological data and mechanical properties of the coronary vessels. We examine the effect of percent diameter stenosis on blood flow rate and shear stress for two cases. Case I comprised of one-stenosed element at $10^{th}$ order ($\%$ diameter stenosis are 10, 30, and 50, respectively). Case II consisted of completely occluded element at $10^{th}$ order (number of occluded elements are 0, 1, and 2 out of 8, respectively). As the level of stenosis becomes severe, the shear stress increases significantly but the flow rate reduction was relatively small. However, for the occluded case, there was linearly proportional reduction of flow rate according to number of occluded elements. Either such high shear stress associated with coronary artery stenosis or reduced flow rate due to occlusion may cause atherosclerosis and myocardial ischemia.

Measurement of red cell deformability and whole blood viscosity using laser-diffraction slit rheometer

Sehyun Shin,서장수,Yunhee Ku,Myung-Su Park 한국유변학회 2004 Korea-Australia rheology journal Vol.16 No.2

Deformability of Red Blood Cells : A Determinant of Blood Viscosity

Sehyun Shin,Yunhee Ku,Myung-Su Park,Jang-Soo Suh 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.1

The suspension of hardened red blood cells (RBCs) differs from the suspension of normal RBCs with respect to their rheological behavior. The present study investigated the effect of deformability of RBCs on blood viscosity. RBC deformability and blood viscosity were measured with a recently developed slit-flow laser-diffractometer and the pressure-scanning capillary viscometer, respectively. At the same level of cell concentration, the viscosity of the hardened RBC suspension is higher than that of the normal RBCs suspension. An increase in cell percentage for hardened RBCs shows the significant increase in the level of blood viscosity compared to the normal RBCs. In addition, it was found that RBC deformability played an important role in reducing viscosity at low shear rates as well as high shear rates. These results present the evidence for the effect of RBC deformability on blood viscosity using newly developed methods, which can be used in early diagnosis of the cardiovascular diseases.

Slit-flow ektacytometry: Laser diffraction in a slit rheometer

Shin, Sehyun,Ku, Yunhee,Park, Myung-Su,Suh, Jang-Soo WILEY - LISS 2005 CYTOMETRY PART B CLINICAL CYTOMETRY Vol.b65 No.1

<B>Background</B><P>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.</P><B>Methods</B><P>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.</P><B>Results</B><P>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.</P><B>Conclusions</B><P>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. © 2005 Wiley-Liss, Inc.</P>

Simultaneous Measurement of red Blood Cell Aggregation and Viscosity : Light Transmission Slit Rheometer

Sehyun Shin,Myung-Su Park,Yunhee Ku,Joo-Hee Jang,Jang-Soo Shu 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.1

Aggregation of red blood cells (RBCs) is a major determinant of blood viscosity. There have not been available techniques for measuring RBC aggregation and viscosity, simultaneously. A laser transmission technique has been combined with a slit rheometry, which shows significant advances in rheometer design, operation and data analysis. A laser beam traverses a blood suspension flowing through a slit and is scattered by RBCs in the volume. The transmitted light is captured by a photodiode, linked to a computer, while the differential pressure variation is measured by a pressure transducer. Both measurements of the laser-transmitted intensity and pressure with respect to time enable to determine the aggregation index and the viscosity. The advantages of this design are in its simplicity, i.e., ease of operation and no moving parts, low cost and a short operating time. In addition, the slit-flow aggregometer can be easily used in a clinical setting owing to the incorporation of a disposable element that holds the blood sample.