• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.151-159
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• 2008

The parameter-based cardiovascular impedance simulator that is able to overcome the limits of conventional mock circulatory systems is critical for the development and test of biomedical devices including artificial heart. The concept of impedance simulator was validated mathematically in a previous study using high-gain feedback linearization control which, however, may cause serious difficulties and limits for practical implementation. In this study, therefore, practical applicability of the impedance simulator is investigated considering the physical limits such as motor speed and torque. Simple PID controller which do not require complex model of the simulator is used considering the practical implementation. Design guidelines of the impedance simulator are also provided based on the results.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.11 no.1
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• pp.82-104
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• 2007

Purpose: We performed this study to examine the effect of controlled respiration on cardiovascular system in healthy adult subjects using impedance cardiography and photoplethysmography. Materials and Methods: This study had performed on 74 subjects, which were healthy men and women without a experience of respiration practice. Using the instruments for impedance cardiography and photoplethysmography, parameters of each subject had been measured after each controlled respirations which were natural respiration, controlled natural respiration (I:E=1.1.6), longer inspiration(I:E=3:3), and longer expiration(I:E=2:4). The measured parameters of impedance cardiography and photoplethysmography were processed statistically by one-way repeated ANOVA. Results: 1. HR and CI of impedance cardiography were decreased significantly during controlled respiration comparing with the result of basal state(the state of enough break). There was no significant difference among the results of controlled respiration. 2. PEP of impedance cardiography had no significant difference among the result of basal state and the results of controlled respiration(p=0.059). 3. VI of impedance cardiography had significant differences among the result of basal state and the results of controlled respiration, and decreased continuously through the controlled respiration. 4. b/a of photoplethysmography had no significant difference among the result of basal state and the results of controlled respiration(p=0.554). 5. c/a of photoplethysmography were decreased significantly during controlled respiration comparing with the result of basal state. There was no significant difference among the results of controlled respiration. 6. d/a of photoplethysmography had significant differences among the results of the controlled respiration decreasing continuously through the controlled respiration and had no significant difference between the result of basal state and the result of natural respiration. 7. AGI of photoplethysmography had significant differences among the result of basal state and the results of the controlled respiration increasing continuously through the controlled respiration. Conclusion: We had examined the effects of controlled respirations on cardiovascular system in multiple points of view. The effects of controlled respirations on cardiovascular system can't be explained in a simple way, as the cardiovascular system is controlled by many factors. Therefore, more physiological parameters must be measured in the future study on the effect of the controlled respiration on human cardiovascular system.

• 한국초전도학회:학술대회논문집
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• v.16
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• pp.8-8
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• 2006

• Journal of Chest Surgery
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• v.28 no.11
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• pp.973-976
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• 1995

The assessment method of human body composion by bioelectrical impedance is very simple, safe, rapid and noninvasive. Based on prediction formulas for total body water from bioelectrical impedance, the observed weight loss should be associated with an increase in impedance. However in edematous patients for dialysis, the calculated total body water loss as calculated from impedance were overestimated and significantly higher than the weight loss after dialysis. So determination of impedance were made in 50 edematous patients before, during and after dialysis. Mean weight loss, which was assumed to be only loss of water was 1719$\pm$ 866 gr and mean impedance change was 71.0 $\pm$ 23.0 Ohm under 50kHz. Body weight loss was highly correlated [r>0.81 with the increase in body impedance under variable frequencies[1, 10, 20, 30, 40, 50 kHz . But there were no differences between frequences. In conclusion, clinical application of bioelectrical impedance method is useful for individual edematous patients with new correlation equation[Y=230+26.8X, X;Impedance change, Y;Calculated total body water loss .

• Journal of Advanced Navigation Technology
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• v.18 no.6
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• pp.582-587
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• 2014

This study have researched on feasibility of bioelectrical impedance analysis (BIA, which is simple useful evaluation tool for predictive factor of cardiovascular disease) to patients who have to travel along the sea for a long-period time and have difficulty in visiting medical institutions. We studied on the basis of total cholesterol value, which is nowadays widely used tool for predictive factor of cardiovascular disease, and also studied its association with BIA value via statistical analysis. Our result showed correlation with fat thickness of individual sites, and especially, fat thickness of left thigh showed high relation with total cholesterol value. This result shows that people who are in travel of long-period of time at sea are feasible of using BIA to evaluate changes of left thigh fat thickness as predictive factor for cardiovascular disease. Due to lack of advanced researches further studies should be done. And based on special circumstances in sea, more studies should be done to validity concerning this circumstances and accuracy of this evaluation tool.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.8
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• pp.1251-1255
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• 2015

The purpose of this study is to measurement the cardiac output using hand to hand impedance method to provide convenience to user when measuring SV(stroke volume) with the use of ICG(Impedance Cardiography). We suggest the optimized modified formula, which can be applied when using impedance with the use of hand to hand Impedance. To verify this formula, a SV from transthoracic approach and hand to hand approach are compared for the 36 subjects, respectively. The acquired data was analyzed by using LabVIEW 8.6, analysis was implemented by SPSS 12.0. Fine difference was shown by individual. We showed that as a result of analyzing the ICG measurement value on thoracic and hand to hand, the correlation with SV was r=0.716, thereby having indicated the results of regression model in relatively high correlation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.5
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• pp.702-712
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• 2016

A wrist watch type wearable cardiovascular monitoring device is proposed for continuous and convenient monitoring of the patient's cardiovascular system. For comprehensive monitoring of the patient's cardiovascular system, the concurrent electrocardiogram (ECG) and arterial pulse wave (APW) sensor front-end are fabricated in $0.18{\mu}m$ CMOS technology. The ECG sensor frontend achieves 84.6-dB CMRR and $2.3-{\mu}Vrms$-input referred noise with $30-{\mu}W$ power consumption. The APW sensor front-end achieves $3.2-V/{\Omega}$ sensitivity with accurate bio-impedance measurement lesser than 1% error, consuming only $984-{\mu}W$. The ECG and APW sensor front-end is combined with power management unit, micro controller unit (MCU), display and Bluetooth transceiver so that concurrently measured ECG and APW can be transmitted into smartphone, showing patient's cardiovascular state in real time. In order to verify operation of the cardiovascular monitoring system, cardiovascular indicator is extracted from the healthy volunteer. As a result, 5.74 m/second-pulse wave velocity (PWV), 79.1 beats/minute-heart rate (HR) and positive slope of b-d peak-accelerated arterial pulse wave (AAPW) are achieved, showing the volunteer's healthy cardiovascular state.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.11 no.2
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• pp.128-140
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• 2007

Purpose: We performed this study to examine the correlationship between EEG complexity and impedance cardiography data using correlation analysis. Method: This study performed on 30 healthy subjects(16 males, 14 females). Before and after natural respiration, ICG data were recorded, and EEG raw data were measured by moving windows during 15 minutes. The correlation dimension(D2) was calculated from 15 minutes data. 8 channels EEG data were analysed with 9 index of ICG data by correlation analysis. Result: 1. ACI of impedance cardiography had significant correlationship with ch.4 of EEG complexity(p=0.03). 2. VI of impedance cardiography had significant correlationship with ch.3 of EEG complexity(p=0.034) and ch.4 of EEG complexity(p=0.017). 3. HR, TFC, PEP, LVET, STR of impedance cardiography had no significant correlationship with all of 8 channel EEG complexity. Conclusions: These results suggest that nonlinear analysis of EEG and impedance cardiography have some significant correlationship. And it can make out relationship between brain system and cardiovascular system. In the future, therefore, more study of these fields are necessary.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.849-856
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• 2009

Truncal obesity associated with insulin resistance and metabolic syndrome increase the likelihood of hypertension, various cardiovascular diseases, hyperlipidemia and coronary heart diseases. International Diabetes Federation (IDF) experts recognized that it is necessary to develop the simple diagnostic tool which is applicable to diagnose truncal obesity worldwide, and proposed the method using a waist circumference but there is a limit to estimate subcutaneous fat distribution. However, waist line is also influenced by total fat capacity less than the intra abdominal fat. The more having severe obesity, the more correlation coefficient between waist line and intra abdominal fat is low. Therefore, this thesis defines a new abdominal impedance measurement position and impedance-index to analysis central obesity. This proposes the new model to estimate abdominal obesity using the abdominal impedance-index and CT images acquired fro 160 Korean subjects. The proposed model shows that the abdominal fat distribution has a higher correlation than waist line. (Adj R2=0.809, 0.667 and 0.687 with abdominal fat area, visceral fat area and subcutaneous fat area respectively).

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.10
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• pp.494-501
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• 2001

In this study, the effects of vascular parameter changes and electrodes on VOP measurement based on IPG were simulated mathematically. For the evaluation of the effects of hemodynamic changes on VOP, a mathematical model, which consists of cardiovascular system model and venous occlusion model, was developed and the model solution representing the blood flow and pressure in measuring point was found by 2nd order Runge-Kutta method. And, with sensitivity coefficients obtained from finite element solution of electric field in measuring point, the effects of electrode system on measurement were evaluated. As increasing the resistance, the venous capacitance was not changed but the venous outflows were decreased and the decreased compliance reduced the venous capacitance. And, for several configurations of round electrodes and band electrodes, the sensitivity coefficients were computed using the electric field distribution along deep vein. In conclusion, the proposed mathematical cardiovascular model could be applied to the simulation study on the effects of hemodynamic parameters on DVT diagnosis with IPG. And, also the sensitivity coefficients could provide effective electrode configuration for exact measurement of VOP.