Jia-Jung Wang

Reduction of interference in oscillometric arterial blood pressure measurement using fuzzy logic

In oscillometry, oscillation amplitudes (OAs) embedded in the cuff pressure are drastically affected by a variety of artifacts and cardiovascular diseases, leading to inaccurate arterial blood pressure (ABP) measurement. The purpose of this paper is to improve the accuracy in the arterial pressure measurement by reducing interference in the OAs using a recursive weighted regression algorithm (RWRA). This method includes a fuzzy logic discriminator (FLD) and a recursive regression algorithm. The FLD is used to reduce the effect of artifacts caused by measurement motion disturbance or cardiovascular diseases, and to determine the truthfulness of the oscillation pulse. According to the truth degree, the relationship between the cuff pressure and OA is reconstructed using the regression algorithm. Because the regression method must utilize inverse matrix operation, which will be difficult to implement in an automatic or ambulatory monitor, the recursive regression method is proposed to solve this problem. To test the performance of this RWRA, 47 subjects underwent the ABP measurement using both the auscultation and the oscillometry combined with the RWRA. It was found that the average difference between the pooled blood pressures measured by the auscultation and those by the oscillometry combined with the RWRA was found to be only 4.9 mmHg. Clinical results demonstrated that the proposed RWRA is more robust than the traditional curve fitting algorithm (TCFA). We conclude that the proposed RWRA can be applied to effectively improve the accuracy of the oscillometric blood pressure measurement.

Model-based synthetic fuzzy logic controller for indirect blood pressure measurement

In this paper, a new measurement system for the noninvasive monitoring of the continuous blood pressure waveform in the radial artery is presented. The proposed system comprises a model-based fuzzy logic controller, an arterial tonometer and a micro syringe device. The flexible diaphragm tonometer registers the continuous blood pressure waveform. To obtain accurate measurement without distortion, the tonometers mean chamber pressure must be kept equal to the mean arterial pressure (MAP), the so-called optimal coupling condition, such that the arterial vessel has the maximum compliance. Since the MAP cannot be measured directly, to keep the optimal coupling condition becomes a tracking control problem with unknown desired trajectory. To solve this dilemma, a model-based fuzzy logic controller is designed to compensate the change of MAP by applying a counter pressure on the tonometer chamber through the micro syringe device. The proposed controller consists of a model-based predictor and a synthetic fuzzy logic controller (SFLC). The model-based predictor estimates the MAPs changing tendency based on the identified arterial pressure-volume model.

Assessment of Stroke Volume From Brachial Blood Pressure Using Arterial Characteristics

Goal: The goal of this study is to present a modified pulse contour method to estimate the stroke volume (SV) based on an oscillometric sphygmomanometer. Methods: The pulse contour was extracted from the pulse signal of the cuff pressure. The characteristics of the brachial artery, as well as the compliance (Cartery) and time constant τ of the Windkessel model, could be determined and used to estimate the SV once the apparatus finished the blood pressure measurement. Results: Assessments of the SV by echocardiography and our method were carried out in 55 subjects. The change in the brachial arterial volume obtained by our method was significantly correlated with that of the two-dimensional ultrasound method (rv = 0.871). The estimated SV values by our method for male and female groups, SVestimate, were also significantly correlated with the echocardiography results, SVref (rmale = 0.680, rfemale = 0.706). The Bland-Altman plot showed agreement between SVref and SVestimate, with all data points contained within the limits of agreement (± 2 SD). The mean difference and standard deviation (mean ± SD) were 0.101 ± 14.880 ml and 0.650 ± 11.990 ml for the male and female groups, respectively. Conclusion: The blood pressure, SV, and cardiac output were measured simultaneously, making our method well suited for home use. Significance: Our method was embedded in an oscillometric sphygmomanometer.

A model-based fuzzy logic controller for tracking mean arterial pressure

Proposes a noninvasive measurement method for tracking the tendency of mean arterial pressure in the radial artery. The designed system consists of a tonometer, a micro syringe device, and a model-based fuzzy logic controller. The proposed control system consists of a linear predictor, and a synthetic fuzzy logic controller. The design of the fuzzy rules in each subcontroller is based on the oscillometric principle saying that the arterial vessel has the maximum compliance when the detected vessel volume pulse reaches its maximum amplitude.

An autometic system for ECG arrhythmias classification

An automatic system integrating the artificial intelligent methods could classify the normal sinus rhythm (NSR) and three arrhythmic types from the continuous ECG signals obtained from the MIT-BIH arrhythmia database. In this system, a support vector machine (SVM) was used to mark the heart beats of ECG with Lead II and its slope signals. An algorithm according the markers extracted segments waveforms of Lead II and V1 as the patterns features of classification. A self-constructing neural fuzzy inference network (SoNFIN) was used to classify NSR and three arrhythmic types including premature ventricular contraction (PVC), left bundle branch block (LBBB), and right bundle branch block (RBBB). The results indicated the accuracy achieved 98.9%. The accuracy of heart beat detection could be arisen to 99.3%.

Exercise muscle fatigue detection system implementation via wireless surface electromyography and empirical mode decomposition

Surface electromyography (sEMG) is an important measurement for monitoring exercise and fitness. A wireless Bluetooth transmission sEMG measurement system with a sampling frequency of 2 KHz is developed. Traditional muscle fatigue is detected from the median frequency of the sEMG power spectrum. The regression slope of the linear regression of median frequency is an important muscle fatigue index. As fatigue increases, the power spectrum of the sEMG shifts toward lower frequencies. The goal of this study is to evaluate the sensitivity of empirical mode decomposition (EMD) quantifying the electrical manifestations of the local muscle fatigue during exercising in health people. We also compared this method with the raw data and discrete wavelet transform (DWT). Five male and five female volunteers participated. Each subject was asked to run on a multifunctional pedaled elliptical trainer for about 30 minutes, twice a week, and there were a total of six recording times for each subject with a wireless EMG recording system. The results show that sensitivity of the highest frequency component of EMD is better than the highest frequency component of DWT, and raw data.

Non-invasive determination of instantaneous brachial blood flow using the oscillometric method.

Abstract The oscillometric method has been widely used to measure arterial systolic and diastolic blood pressures, but its potential for arterial blood flow measurements still remains to be explored. The aim of this study was to non-invasively determine arterial blood flow using an oscillometric blood flow measurement system. The system consists of a pneumatic elastic cuff, an air-pumping motor, a releaser valve, a pressure transducer, and an airflow meter. To build a non-linear cuff model, we measured airflow pumped into the pneumatic cuff and cuff pressure using an airflow meter and pressure transducer during the inflation period, respectively. During the deflation period, only the pressure transducer was used to record cuff pressure. Based on the cuff model, the oscillometric blood flow waveform was obtained by integrating the oscillometric pressure waveform. We compared arterial blood flow derived from the maximum amplitude of the oscillometric blood flow waveform with Doppler-measured blood flow calculated with the diameters and blood velocities of the brachial arteries in 32 subjects who underwent diagnostic evaluations for peripheral arterial embolism. A linear correlation coefficient of r= 0.716 was found between the oscillometry- and Doppler-based blood flow measurements in the 32 subjects. These results suggest that blood flow passing through the brachial artery can be quantified non-invasively using the oscillometric approach after appropriate calibration.

ESTIMATING THE MEAN BLOOD FLOW OF ARM BASED ON WINDKESSEL MODEL

The blood flow is always used to evaluate the arterial obstruction or arteriosclerosis. The echo-method is the standard. In this study, we propose a new method for assessing the total mean blood flow of the arm using a known brachial arterial compliance and based on a two-element Windkessel (WK) model, in which the arterial hemodynamics consists of a peripheral arterial resistor and a peripheral arterial capacitor in parallel. The known compliance of the brachial artery belonging to a local and relative amount has been estimated from the pattern of the oscillometric waveform in our previous study. An estimating peripheral arterial compliance and resistance are got from the known compliance. The governing equation of the two-element WK model is then used to get the blood flow waveform. The accuracy of WK-based mean blood flow (FWK) is validated by comparing it with the mean blood flow (Fecho) estimated by an echo-based method in the brachial arteries of 32 subjects. The results showed that the values of FWK and Fecho were significantly correlated (r = 0.671). This suggests that a total mean blood flow can be evaluated by the known arterial compliances derived by regional or relative changed measurements.

Improvement of Left Ventricular Ejection Time Measurement in the Impedance Cardiography Combined with the Reflection Photoplethysmography

Cardiac stroke volume (SV) is an essential hemodynamic indicator that can be used to assess whether the pump function of the heart is normal. Non-invasive SV measurement is currently performed using the impedance cardiography (ICG). In this technology, left ventricular ejection time (LVET) is an important parameter which can be determined from the ICG signals. However, the ICG signals are inherently susceptible to artificial noise interference, which leads to an inaccurate LVET measurement and then yields an error in the calculation of SV. Therefore, the goal of the study was to measure LVETs using both the transmission and reflection photoplethysmography (PPG), and to assess whether the measured LVET was more accurate by the PPG signal than the ICG signal. The LVET measured by the phonocardiography (PCG) was used as the standard for comparing with those by the ICG and PPG. The study recruited ten subjects whose LVETs were simultaneously measured by the ICG using four electrodes, the reflection PPG using neck sensors (PPGneck) and the transmission PPG using finger sensors (PPGfinger). In each subject, ten LVETs were obtained from ten heartbeats selected properly from one-minute recording. The differences of the measured LVETs between the PCG and one of the ICG, PPGneck and PPGfinger were −68.2 ± 148.6 ms, 4.8 ± 86.5 ms and −7.0 ± 107.5 ms, respectively. As compared with the PCG, both the ICG and PPGfinger underestimated but the PPGneck overestimated the LVETs. Furthermore, the measured LVET by the PPGneck was the closest to that by the PCG. Therefore, the PPGneck may be employed to improve the LVET measurement in applying the ICG for continuous monitoring of SV in clinical settings.

Using the system identify theorem for constructing the dynamic compliance of the brachial artery

A noninvasive measurement technique with oscillometry, system identify, and the related measured circuits is investigated to detect the dynamic compliance of brachial artery. In oscillometry, oscillation amplitudes (OAs) embedded in the cuff pressure are effected by the arterial characteristic, body tissue, and cuff characteristic. In cuff deflation, pressure transducer and micro flower meter were used to detect the variation of cuff pressure and volume. A system identify theorem was used to reconstruct the cuff model. Using the cuff pressure and OAs, the arterial volume change was calculated under the different transmural pressure. This measurement system also detected the systolic and diastolic pressure, simultaneously. Therefore, the dynamic pressure-volume (P-V) curve of artery was made.