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Liau B.-Y.,Hungkuang University | Yeh S.-J.,Section of Neurology and Neurophysiology | Chiu C.-C.,Feng Chia University
Computing in Cardiology | Year: 2010

In this study, time-domain cross-correlation function was applied to evaluate the relationship between blood pressure and cerebral blood flow velocity signals acquiring from healthy subjects and stroke patients both in supine and head-up tilt positions to evaluate the effect of posture change. 10 stroke patients and 11 healthy subjects were included in this study. Results revealed that the mean arterial blood pressure (MABP) values of stroke patients in response to posture changes were reduced. However, MABP values in healthy subjects were become higher in head-up tilt position. Both of MABP values of healthy subjects in supine and head-up tilt were significantly lower than those in stroke patients (p<0.05). On the other hand, mean cerebral blood flow velocity (MCBFV) in healthy subjects remain constant. However, the values in stroke patients reduced in response to headup tilt. In the results of cross-correlation function (CCF) analysis, max CCF values in healthy subjects were significantly higher than those in stroke patients (p<0.05) in both supine and head-up tile positions. It might indicate correlation of MABP and MCBFV was higher in healthy subjects. The max CCF index in stroke patients were close to 0 second in both positions (supine: - 0.35±3.36 sec; head-up tilt:-0.29±3.20 sec). In healthy subjects, max CCF values should be around 2 seconds. Hence, it indicated the phase difference almost did not exist between MABP and MCBFV. This reveals the buffer function of CA were lower in stroke patients. Therefore, CA in stroke patients might be impaired by the results in response to posture changes. Source


Liau B.-Y.,Hungkuang University | Yeh S.-J.,Section of Neurology and Neurophysiology | Chiu C.-C.,Feng Chia University
Computing in Cardiology | Year: 2010

Cardiovascular diseases are common nowadays. The main purpose of this research is to integrate the analysis of blood pressure, cerebral blood flow and heart rate to evaluate coupling effect in stroke patients. There are 10 stroke patients (56±10.6 years) included in this study. Results of blood pressure and cerebral blow velocity values in stroke are lower than those in healthy persons (p<0.05). Low frequency power of blood pressure and cerebral flow velocity are also decreased more than those in healthy subjects (p<0.05), it might be the effect of sympathetic nerve system. K2 means "chaoticness". K2 values of cerebral flow velocity and mean heart rate in stroke subjects are higher than those in healthy subjects significantly (p<0.05), it might indicate cerebral flow and heart rate in stroke are more chaotic. The values of baroreflex sensitivity in healthy subjects are also higher significant (p<0.05). The values of independence of complexity and predictability of blood pressure, cerebral flow and heart rate between 0 and 1 indicate they are highly coupled. Therefore, if the correlation of blood pressure, cerebral flow and heart rate can be observed simultaneously, and the coupling degree of cerebral autoregulation and baroreflex can be investigated, the effect of diagnosis of cardiovascular diseases can be improved. Source


Chiu C.-C.,Feng Chia University | Hai B.H.,Feng Chia University | Yeh S.-J.,Section of Neurology and Neurophysiology
IFMBE Proceedings | Year: 2013

Improving the quality of sleep is an important issue for many researches. A number of biomedical signals, such as EEG, EMG, and EOG were used to classify sleep stages. Based on those signals, one can detect and diagnose the sleep related disorders. There were many researches focused on automatic sleep stages classification. In this research, a new classification method is presented by applying Elman neuron network combined with fuzzy rules and features are extracted by wavelets packets. Nine subjects were recruited from Cheng-Ching General Hospital, Taichung, Taiwan. The sampling frequency is 250Hz and the single channel (C3-A1) EEG signal was acquired for each subject. Combined network was used to recognize the sleep stages in each epoch (a 10 second segment data). The classification results relied on the strong points of neural network and fuzzy logic with average sensitivity is 88.48%, average specificity achieves 95.96%, and average accuracy is 93.79%. The data samples and the length of sleep intervals will be increased for experiment in the future to improve the accuracy. © 2013 IFMBE. Source


Liau B.-Y.,Hungkuang University | Yeh S.-J.,Section of Neurology and Neurophysiology
IFMBE Proceedings | Year: 2013

In this study, cross-correlation function (CCF) were applied to assess the correlation between systolic arterial blood pressure and mean heart rate signals acquiring from stroke and hypertension patients both in supine and head-up tilt positions to evaluate the difference of high blood pressure on baroreflex. 11 hypertension patients (50.1±10.3 years) and 10 stroke patients (56.0±10.1 years) were included in this study. Mean arterial blood pressure level in these two group did not show significant difference (stroke: supine: 117.99 mmHg; tilt:112.25mmHg,; hypertension: supine:107.04 mmHg; tilt: 105.54mmHg, p>0.05). Results revealed that cardiac-baroreceptor sensitivity (BRS) and α index values in these two groups were not significantly different (p>0.05) during supine and headup tilt positions. However, α index values in stroke and hypertension patients reduced in response to head-up tilt (stroke: supine:10.21; tilt:7.14, p<0.05 ; hypertension: supine:11.25; tilt: 7.52, p<0.05). In the results of CCF analysis, it did not showed significant difference in CCF parameters between these two groups during supine position. However, max CCF index (sec) decreased significantly (p<0.05) in hypertension group during head-up tilt. The decreasing time lag might indicate baroreflex disturbance function. Therefore, baroreflex function might be different between hypertension and stroke patients in response to head-up tilt. On the other hand, max CCF index values were significantly lower (p<0.05) in hypertension group than those in stroke group during head-up tilt position. Due to max CCF index stands for phase lag, phase lag in hypertension was lower than that in stroke group. In conclusion, both stroke and hypertension patients were in high blood pressure, but correlation between blood pressure and hear rate was different. It might be the cause and effect of high blood pressure was different. The results could provide another way to look insight the baroreflex and correlation between blood pressure and heart rate. © 2013 Springer-Verlag. Source


Liau B.-Y.,Hungkuang University | Yeh S.-J.,Section of Neurology and Neurophysiology
IFMBE Proceedings | Year: 2013

In this study, time, frequency domain analyses and cross-correlation function (CCF) were applied to evaluate the relationship between systolic arterial blood pressure and mean heart rate signals acquiring from healthy subjects and hypertension patients both in supine and head-up tilt positions to evaluate the effect of antihypertensive drug treatment on baroreflex. 11 hypertension patients (50.1±10.3 years) and 11 healthy subjects (58.4±8.4 years) were included in this study. Results revealed that baroreflex before treatment, cardiacbaroreceptor sensitivity (BRS) values in healthy subjects were significantly higher (p<0.05) than those in hypertension patients in both supine and head-up tilt positions (average BRS value; healthy (supine: 7.3; tilt: 6.4), Hypertension (supine: 6.1; tilt: 5.6)). On the other hand, BRS tend to those in healthy subjects after 2 months of treatment (p>0.05). It might indicate hypertension could affect baroreflex function but the treatment could lead the function of baroreflex tend to those in healthy groups. The values of α index indicated the significant difference (p<0.05) in hypertension group in response to headup tilt (supine: 11.3; tilt: 7.5). In the results of CCF analysis, it showed the man CCF index (sec) maintained in response to head-up tilt (p>0.05). However, max CCF index (sec) reduced significantly (p<0.05) before and after treatment. It indicated the phase between systolic blood pressure and mean heart rate in healthy group was different from that in hypertension group. Hypertension might affect regulation function due to blood pressure level. On the other hand, max CCF value would increase in tilt position for healthy and hypertension groups. However, before and after treatment, max CCF values in hypertension group were significantly higher than those in healthy groups (p<0.05). It might reveal hypertension raise the correlation between blood pressure and heart rate, even after 2 months of treatment. © 2013 Springer-Verlag. Source

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