Hyung-Ro Yoon

Improvement of Dynamic Respiration Monitoring Through Sensor Fusion of Accelerometer and Gyro-sensor

In this paper, we suggest a method to improve the fusion of an accelerometer and gyro sensor by using a Kalman filter to produce a more high-quality respiration signal to supplement the weakness of using a single accelerometer. To evaluate our proposed algorithm’s performance, we developed a chest belt-type module. We performed experiments consisting of aerobic exercise and muscular exercises with 10 subjects. We compared the derived respiration signal from the accelerometer with that from our algorithm using the standard respiration signal from the piezoelectric sensor in the time and frequency domains during the aerobic and muscular exercises. We also analyzed the time delay to verify the synchronization between the output and standard signals. We confirmed that our algorithm improved the respiratory rate’s detection accuracy by 4.6% and 9.54% for the treadmill and leg press, respectively, which are dynamic. We also confirmed a small time delay of about 0.638 s on average. We determined that real-time monitoring of the respiration signal is possible. In conclusion, our suggested algorithm can acquire a more high-quality respiration signal in a dynamic exercise environment away from a limited static environment to provide safer and more effective exercises and improve exercise sustainability.

Non-Invasive Estimation of Systolic Blood Pressure and Diastolic Blood Pressure Using Photoplethysmograph Components

Purpose Photoplethysmography (PPG) is a noninvasive optical technology that detects changes in blood volume in the vascular system. This study aimed to investigate the possibilities of monitoring the cardiovascular system status by using PPG. Materials and Methods Forced hemodynamic changes were induced using cardiac stimulants; dopamine and epinephrine, and PPG components were recorded by a noninvasive method at the peripheral blood vessels. The results were compared among 6 dogs. Endotracheal intubation was performed after an intramuscular injection of 25 mg/kg ketamine sulfate, and anesthesia was maintained with 2% enflurane. After stabilizing the animals for 15 min, 16 mg/mL diluted dopamine was injected into a vein for 2 min at 20 µg/kg· min-1 by using an infusion pump. Thereafter, the infusion pump was stopped, and 1 mg epinephrine was injected intravenously. Fluid administration was controlled to minimize preload change in blood pressure. Results After stimulant administration, systolic blood pressure (SBP) and diastolic blood pressures (DBP) increased. The direct current (DC) component, which reflects changes in blood volume, decreased while the alternating current (AC) component, which reflects changes in vascular compliance and resistance, increased. The correlation coefficient between SBP and the foot of the DC component was 0.939 (p < 0.01), while it was 0.942 (p < 0.01) for DBP and the peak of the DC component. The AC component could predict the increase in vascular resistance from a stable pulse blood volume, even with increased pulse pressure. Conclusions These results support the possibility that PPG components may be used for easy and noninvasive measurement of hemodynamic changes in the cardiovascular system.

Design of a wavelet interpolation filter for enhancement of the ST-segment

A wavelet interpolation filter (WIF) is designed for the removal of motion artifacts in the ST-segment of stress ECGs. The WIF consists of two parts. One part is a wavelet transform that decomposes the stress ECG signal into several frequency bands using a Haar wavelet. The other part is an interpolation method, such as the spline technique, that is used to enhance the reconstruction performance of the signal decomposed by the wavelet transform. To evaluate the performance of the WIF, three indices are used: signal-to-noise ratio (SNR), reconstruction square error (RSE) and standard deviation (SD). The MIT/BIH arrhythmia database, the European ST-T database and the triangular wave are used for evaluation. A noisy ECG signal, corrupted by motion artifacts, is simulated by the addition of two types of random noise to the original ECG signal. For comparison, three indices for the other methods are also computed: mean, median and hard thresholding. The performance of the WIF shows that RSE, SNR and SD are 392.7, 18.3 dB and 2.6, respectively, in the case of a noisy signal with an SNR of 7.1 dB. This result is much better than those for the other methods.

A preliminary study on estimation of energy expenditure at different locations of acceleration sensor during submaximal exercise

The purpose of this study is, for estimating energy expenditure with triaxial accelerometers during exercise, to compare determination coefficients of equations of the estimated regression according to several locations of the accelerometers on the body and then to present an estimation model on the location where there is the least restriction on physical activities. A small portable device that is able to obtain acceleration data during exercise was developed. It was attached on the back, wrist, knee and ankle of the body and then submaximal exercise was conducted on treadmills with the Bruce protocol. For the experimentation, seventeen males of twenties and thirties in good health (27.23±2.18) participated and wore the equipment to analyze respiratory gas, so that the values of acceleration and energy expenditure from the respiratory gas analyzer could be obtained at the same time. The energy expenditure values from the outputs of the respiratory gas equipment were set as a base value, and the accelerations and the physical features of the participants (age, weight, height and BMI) as variables, to check each correlation, and for each of the four locations of the accelerometers on the body, regression analysis was carried out. The results of the experiment are as follows: the correlation between the acceleration and the energy expenditure was the highest on the knee and the lowest on the wrist; but, the determination coefficients (R2) of the regression equations using the continued hours of exercise, weight and acceleration values did not show significant difference among the locations on the body, as the highest R2 = 3D0.873 on the back and the lowest R2 = 3D0.852 on the wrist. This study has shown two possibilities. First, it is possible to predict energy expenditure using accelerometer sensor without respiration gas analyzer in laboratory situation. Second, these findings can be applied to application about predicting conveniently energy expenditure during outdoor activities using accelerometer on watch or shoes.

Compensation on Impedance of the Stratum Corneum

This study aims at compensation of the skin moisture level using skin impedance and SR factor. SR factor is related with the current diffusion into the skin layer. To efficiently analyze the current diffusion on the skin model, we used an electromagnetic simulation program called Ansys 10.0 Emag. We confirmed that the measured value decreases as the electric current gets more diffused to the layer below the horny layer. In order to conduct actual experiments based on the simulated result, we manufactured special electrodes with 24 pins by arranging 0.8㎜-diameter electrodes every 0.5㎜, in a 3 × 8 array. By simultaneously achieving both impedance value and SR value of skin with the manufactured electrodes, we compared the skin moisture level using the existing equipment to the skin moisture level applied using the skin impedance as well as the SR factor developed in this study. The correlation coefficient between the skin moisture level achieved from the existing equipment and the reference value was 0.615 (p＜0.01), whereas the correlation coefficient between the skin moisture achieved from the regression equation in this study was 0.677 (p＜0.01). Accordingly, it was confirmed that applying SR factor additionally improves the moisture level more precisely.

Compensation of the Error Rate for the Non-invasive Sphygmomanometer System Using a Tactile Sensor

The Purpose Of This Paper Is To Use A Tactile Sensor To Compensate The Error Rate. Most Automated Sphygmomanometers Use The Oscillometric Method And Characteristic Ratio To Estimate Systolic And Diastolic Blood Pressure. However, Based On The Fact That Maximum Amplitude Of The Oscillometric Waveform And Characteristic Ratio Are Affected By Compliance Of The Aorta And Large Arteries, A Method To Measure The Artery Stiffness By Using A Tactile Sensor Was Chosen In Order To Integrate It With The Sphygmomanometer In The Future Instead Of Using Photoplethysmography. Since Tactile Sensors Have Very Weak Movements, Efforts Were Made To Maintain The Subjects Arm In A Fixed Position, And A 40hz Low Pass Filter Was Used To Eliminate Noise From The Power Source As Well As High Frequency Noise. An Analyzing Program Was Made To Get Time Delay Between The First And Second Peak Of The Averaged Digital Volume Pulse (Δt dvp ), And The Subjects Height Was Divided By Δt dvp To Calculate The Stiffness Index Of The Arteries (Si dvp ). Regression Equations Of Systolic And Diastolic Pressure Using Si dvp And Mean Arterial Pressure (Map) Were Computed From The Test Group (60 Subjects) Among A Total Of 121 Subjects (Age: 44.9±16.5, Male: Female = 40:81) And Were Tested In 61 Subjects To Compensate The Error Rate. Error Rates Considering All Subjects Were Systolic 4.62±9.39㎜hg, And Diastolic 14.40±9.62㎜hg, And Those In The Test Set Were 3.48±9.32㎜hg, And 14.34±9.67㎜hg Each. Consequently, Error Rates Were Compensated Especially In Diastolic Pressure Using Si dvp , Various Slopes From Digital Volume Pulse And Map To Systolic - 1.91±7.57㎜hg And Diastolic 0.05±7.49㎜hg.

Comparison of CWT with DWT for detecting Qrs Complex on Wearable ECG Recorder

Wearable ECG Recorder can detect not only Biosignal but also Motion artifact and other surrounding noises. This study used wavelet transform as a way of removing such noise and compared Continuous Wavelet Transform (CWT) and Discrete Wavelet Transform (DWT). Each transform is designed to optimize the QRS Complex. CWT was designed to detect the Maximum energy scale from QRS Complex. DWT was designed to decompose 8-Levels and to reconstruct detailed coefficient with the frequency of the QRS Complex. To test the performance of two methods, data were collected from MIT-BIH Arrhythmia Database and Wearable ECG Recorder(WER) at the speed of 3km/h, 6km/h, 9km/h, 12km/h. By analyzing the data from two methods, the effectiveness for detecting QRS Complex while eliminating the surrounding noises.

A Research for evaluation on stress change via thermotherapy and massage

In this research, a device, which has a thermotherapic and massaging function and relaxes muscles, was used to evaluate the effect muscle relaxation has on stress relief. Therefore, the physiological changes namely Heart Rate (HR), Heart Rate Variability (HRV) and Skin Temperature (SKT) of the subjects which reflect the autonomic nervous system and cardiovascular relationship were obtained and analyzed. In order to evaluate the assumption that the treatment relieves the subjects physiological and psychological stress, experiment was carried out on 25 adults (13 male and 12 female, age 52.32±18.121) through stages consisted of relaxation, pre-treatment, treatment and post-treatment. Treatment was provided to the back, stomach and leg area by massaging 55°C heat to the back. According as the physiological changes of subjects before and after treatment were compared, the present research was able to prove that thermotherapy and massage treatment induces physiological change of patients thus relieves stress.

An adaptive M-wave canceler for the EMG controlled functional electrical stimulator and its FPGA implementation

Biopotential signals have been used as command and feedback signals in systems using electrical stimulation of motor nerves to restore the lost function. In order to use the voluntary electromyography (EMG) as a control signal for the functional electrical stimulation of the same muscle, it is necessary to suppress the M-wave evoked by the electrical stimulation. We present a Gram-Schmidt (GS) prediction error filter which effectively eliminates the M-wave from voluntary EMG. The GS filter has systolic array structure, so it offers advantages for the real-time processing on the field programmable gate array (FPGA). On basis of the data obtained from model for M-wave and voluntary EMG and from CNS injury patient, the proposed GS filter showed a very promising performance.

Mathematical model of venous occlusion plethysmography for diagnosing deep vein thrombosis

Although the results of venous occlusion plethysmography (VOP) can determine the existence of deep vein thrombosis (DVT), it is difficult to analyze quantitatively the effects of the degrees of thrombosis, blood pressure and cuff pressure on VOP. In this paper, by developing a combined model that is composed of a pulsatile cardiovascular model and a venous occlusion model, we showed the availability of a more realistic simulation. Using the proposed combined model for simulation of the effects of different head pressures and degrees of thrombosis on VOP, we can achieve a basic understanding of the relationship between the state of the patient and indirect measurements such as impedance plethysmography (IPG) and strain gauge plethysmography (SPG).