A variable-bit-rate characteristic waveform interpolation （VBR-CWI） speech codec with about 1.8 kbit/s average bit rate which integrates phonetic classification into characteristic waveform （CW） decomposition is p...A variable-bit-rate characteristic waveform interpolation （VBR-CWI） speech codec with about 1.8 kbit/s average bit rate which integrates phonetic classification into characteristic waveform （CW） decomposition is proposed. Each input frame is classified into one of 4 phonetic classes. Non-speech frames are represented with Bark-band noise model. The extracted CWs become rapidly evolving waveforms （REWs） or slowly evolving waveforms （SEWs） in the cases of unvoiced or stationary voiced frames respectively, while mixed voiced frames use the same CW decomposition as that in the conventional CWI. Experimental results show that the proposed codec can eliminate most buzzy and noisy artifacts existing in the fixed-bit-rate characteristic waveform interpolation （FBR-CWI） speech codec, the average bit rate can be much lower, and its reconstructed speech quality is much better than FS 1 016 CELP at 4.8 kbit/s and similar to G. 723.1 ACELP at 5.3 kbit/s.展开更多
Heart rate variability （HRV） refers to the variations between consecutive heartbeats, which depend on the continuous modulation of the sympathetic and parasympathetic branches of the autonomic nervous system. HRV ha...Heart rate variability （HRV） refers to the variations between consecutive heartbeats, which depend on the continuous modulation of the sympathetic and parasympathetic branches of the autonomic nervous system. HRV has been shown to be effective as a predictor of risk after myocardial infarction and an early warning sign of diabetic neuropathy, and in the cardiology setting is now recognized to be a useful tool for risk-stratification after hospital admission and after discharge. Recent evidences suggest that HRV analysis might predict complications even in patients undergoing cardiac surgery, and the present review summarizes the importance of HRV analysis in adult cardiac surgery and the perspectives for HRV use in current clinical practice. Although future larger studies are warranted before HRV can be included into daily clinical practice in adult cardiac surgery, HRV is a novel tool which might detect autonomic instability in the early postoperative phase and during hospital stay, thus predicting or prompt-diagnosing many of the post-operative complications.展开更多
Objective A novel index based on fi-equency-domain analysis of heart rate variability （HRV） was tested on patients with reduced left ventricular systolic function. This index, namely VHFI, was defined as the very hi...Objective A novel index based on fi-equency-domain analysis of heart rate variability （HRV） was tested on patients with reduced left ventricular systolic function. This index, namely VHFI, was defined as the very high frequency （VHF） component of the power spectrum normalized to represent its relative value in proportion to the total power minus the very low frequency component. Methods Patients （n = 130） were divided into a study group, consisting 66 patients with decreased left ventricular systolic function, and a control group, consisting 64 patients with normal heart structure and function and without severe coronary artery stenosis （〈 50%）. Results VHFI in the study group was significantly higher than that in the control group （19.17 ± 13.35 vs 11.37 ± 10.77, P 〈 0.001）. Cardiac events occurred in 18 patients during follow-up （33.34 i 3.26 months）. Defining the positive test as VHFI =15 and negative test as VHFI 〈15, achieved a sensitivity of 57.58% and a specificity of78.13% for predicting decreased left ventricular systolic function, and achieved a sensitivity of 66.67% and a specificity of 64.29% for predicting cardiac events. Univariate Cox regression analysis showed that positive VHFI test was an independent variable in predictive cardiac events. Conclusions The results suggest that VHFI is a useful tool for quick evaluation of left ventricular systolic function and prediction of prognosis展开更多
Objective: To introduce a method to calculate cardiovascular age, a new, accurate and much simpler index for assessing cardiovascular autonomic regulatory function, based on statistical analysis of heart rate and bloo...Objective: To introduce a method to calculate cardiovascular age, a new, accurate and much simpler index for assessing cardiovascular autonomic regulatory function, based on statistical analysis of heart rate and blood pressure variability (HRV and BPV) and baroreflex sensitivity (BRS) data. Methods: Firstly, HRV and BPV of 89 healthy aviation personnel were analyzed by the conventional autoregressive (AR) spectral analysis and their spontaneous BRS was obtained by the sequence method. Secondly, principal component analysis was conducted over original and derived indices of HRV, BPV and BRS data and the relevant principal components, PCi orig and PCi deri (i=1, 2, 3,...) were obtained. Finally, the equation for calculating cardiovascular age was obtained by multiple regression with the chronological age being assigned as the dependent variable and the principal components significantly related to age as the regressors. Results: The first four principal components of original indices accounted for over 90% of total variance of the indices, so did the first three principal components of derived indices. So, these seven principal components could reflect the information of cardiovascular autonomic regulation which was embodied in the 17 indices of HRV, BPV and BRS exactly with a minimal loss of information. Of the seven principal components, PC2 orig , PC4 orig and PC2 deri were negatively correlated with the chronological age ( P <0 05), whereas the PC3 orig was positively correlated with the chronological age ( P <0 01). The cardiovascular age thus calculated from the regression equation was significantly correlated with the chronological age among the 89 aviation personnel ( r =0.73, P <0 01). Conclusion: The cardiovascular age calculated based on a multi variate analysis of HRV, BPV and BRS could be regarded as a comprehensive indicator reflecting the age dependency of autonomic regulation of cardiovascular system in healthy aviation personnel.展开更多
Moderate exercise contributes to health, but excessive exercise may lead to physicalinjury or even endanger life. It is pressing for a device that can detect the intensity of exercise.Therefore, in order to enable rea...Moderate exercise contributes to health, but excessive exercise may lead to physicalinjury or even endanger life. It is pressing for a device that can detect the intensity of exercise.Therefore, in order to enable real-time detection of exercise intensity and mitigate the risks of harmfrom excessive exercise, a exercise intensity monitoring system based on the heart rate variability(HRV) from electrocardiogram (ECG) signal and linear features from phonocardiogram (PCG)signal is proposed. The main contributions include: First, accurate analysis of HRV is crucial forsubsequent exercise intensity detection. To enhance HRV analysis, we propose an R-peak detectorbased on encoder-decoder and temporal convolutional network (TCN). Experimental resultsdemonstrate that the proposed R-peak detector achieves an F1 score exceeding 0.99 on real high-intensity exercise ECG datasets. Second, an exercise fatigue monitoring system based on multi-signal feature fusion is proposed. Initially, utilizing the proposed R-peak detector for HRV extractionin exercise intensity detection,which outperforms traditional algorithms, with the system achieving a classification performance of 0.933 sensitivity, 0.802 specificity, and 0.960 accuracy. To further improve the system, we combine HRV with the linear features of PCG. Our exercise intensitydetection system achieves 90.2% specificity, 96.7% recall, and 98.1% accuracy in five-fold cross-validation.展开更多
Objective: To elucidate the role of the autonomic nervous system (ANS) in acute mountain sickness (AMS) during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level residents rapidl...Objective: To elucidate the role of the autonomic nervous system (ANS) in acute mountain sickness (AMS) during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level residents rapidly ascended to Tibet plateau (3 675 m altitude) by airplane from Chengdu plain (560 m altitude). ANS function was tested in plain and day 2–4 in Tibet by heart rate variability (HRV), cold pressor test (CPT). AMS was evaluated by clinic symptomatic scores. All subjects were divided into non-AMS group (57, scores≤4) and AMS group (42, scores>4). Results: Compared with non-AMS group, AMS group had higher standard deviation of normal to normal intervals (SDNN), root mean square of delta RR (rMSSD), low-frequency (LF) power, and normalized low-frequency (LFnu) power in plain (P<0.05). After arrival at 3 675 m altitude, AMS group had greater reduction in percentage of delta RR>50 ms(PNN50), rMSSD (P<0.01) and SDNN, LF, total power (TP) (P<0.05). Although no significant differences in the increase of SP and DP during CPT were found between 2 groups in plain, the SP increase during CPT of AMS group was less than non-AMS group (P<0.05) at 3 675 m altitude. AMS symptomatic scores was not only positively correlated with SDNN, rMSSD, LF/HF in plain (P<0.05), but also negatively correlated with HFnu in plain (P<0.05). Conclusion: During the initial high altitude exposure, ANS modulation is generally blunted, but the relatively predominant sympathetic control is enhanced, and this characteristic change of ANS function is positively correlated with the development of AMS.展开更多
Background:Military-related post-traumatic stress(PTS)is associated with numerous symptom clusters and diminished autonomic cardiovascular regulation.Highresolution,relational,resonance-based,electroencephalic mirrori...Background:Military-related post-traumatic stress(PTS)is associated with numerous symptom clusters and diminished autonomic cardiovascular regulation.Highresolution,relational,resonance-based,electroencephalic mirroringis a noninvasive,closed-loop,allostatic,acoustic stimulation neurotechnology that produces realtime translation of dominant brain frequencies into audible tones of variable pitch and timing to support the autocalibration of neural oscillations.We report clinical,autonomic,and functional effects after the use offor symptoms of military-related PTS.Methods:Eighteen service members or recent veterans(15 active-duty,3 veterans,most from special operations,1 female),with a mean age of 40.9(SD=6.9)years and symptoms of PTS lasting from 1 to 25 years,undertook19.5(SD=1.1)sessions over 12 days.Inventories for symptoms of PTS(Posttraumatic Stress Disorder Checklist–Military version,PCL-M),insomnia(Insomnia Severity Index,ISI),depression(Center for Epidemiologic Studies Depression Scale,CES-D),and anxiety(Generalized Anxiety Disorder 7-item scale,GAD-7)were collected before(Visit1,V1),immediately after(Visit2,V2),and at 1 month(Visit3,V3),3(Visit4,V4),and 6(Visit5,V5)months after intervention completion.Other measures only taken at V1 and V2 included blood pressure and heart rate recordings to analyze heart rate variability(HRV)and baroreflex sensitivity(BRS),functional performance(reaction and grip strength)testing,blood and saliva for biomarkers of stress and inflammation,and blood for epigenetic testing.Paired t-tests,Wilcoxon signed-rank tests,and a repeated-measures ANOVA were performed.Results:Clinically relevant,significant reductions in all symptom scores were observed at V2,with durability through V5.There were significant improvements in multiple measures of HRV and BRS[Standard deviation of the normal beat to normal beat interval(SDNN),root mean square of the successive differences(rMSSD),high frequency(HF),low frequency(LF),and total power,HF alpha,sequence all,and systolic,diastolic and mean arterial pressure]as well as reaction testing.Trends were seen for improved grip strength and a reduction in C-Reactive Protein(CRP),Angiotensin II to Angiotensin 1–7 ratio and Interleukin-10,with no change in DNA n-methylation.There were no dropouts or adverse events reported. Conclusion:Service members or veterans showed reductions in symptomatology of PTS,insomnia,depressive mood,and anxiety that were durable through 6 months after the use of a closed-loop allostatic neurotechnology for the autocalibration of neural oscillations.This study is the first to report increased HRV or BRS after the use of an intervention for service members or veterans with PTS.Ongoing investigations are strongly warranted.Trial registration:NCT03230890,retrospectively registered July 25,2017.展开更多
Objective: To investigate the changes of autonomic nervous system (ANS) function during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level male residents were studied in Chengdu ...Objective: To investigate the changes of autonomic nervous system (ANS) function during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level male residents were studied in Chengdu plain and then Tibet plateau. Heart rate variability (HRV), cold pressor test (CPT), resting heart rate (HR) and blood pressure (BP) were measured at baseline (560 m altitude) and in 2 to 4 d after arriving at Tibet plateau (3 675 m altitude) to assess the ANS function. Results: Compared with baseline, on day 2 in Tibet the standard deviation of normal to normal intervals (SDNN), high-frequency (HF) power, total power (TP), root mean square of delta RR (rMSSD), percentage of delta RR>50 ms (PNN50), normalized high-frequency (HFnu) and fractal dimension (FD) decreased significantly (SDNN, HF, TP P<0.01, rMSSD, PNN50, HFnu, FD P<0.05), while the normalized low-frequency (LFnu) and LF/HF increased significantly (P<0.01). During day 3–4 in Tibet, SDNN, rMSSD, HF, TP and HFnu tended to rebound while LFnu and LF/HF decreased towards baseline day by day. In addition, in Tibet the increase in systolic pressure (SP) and diastolic pressure (DP) during CPT decreased significantly (P<0.01, 0.05), but resting HR increased compared with baseline (P<0.01). Conclusion: ANS modulation is generally blunted, and the relatively predominant sympathetic control is enhanced originally, then it reverts to the sea level states gradually during the initial days of acute high-altitude exposure.展开更多
文摘A variable-bit-rate characteristic waveform interpolation （VBR-CWI） speech codec with about 1.8 kbit/s average bit rate which integrates phonetic classification into characteristic waveform （CW） decomposition is proposed. Each input frame is classified into one of 4 phonetic classes. Non-speech frames are represented with Bark-band noise model. The extracted CWs become rapidly evolving waveforms （REWs） or slowly evolving waveforms （SEWs） in the cases of unvoiced or stationary voiced frames respectively, while mixed voiced frames use the same CW decomposition as that in the conventional CWI. Experimental results show that the proposed codec can eliminate most buzzy and noisy artifacts existing in the fixed-bit-rate characteristic waveform interpolation （FBR-CWI） speech codec, the average bit rate can be much lower, and its reconstructed speech quality is much better than FS 1 016 CELP at 4.8 kbit/s and similar to G. 723.1 ACELP at 5.3 kbit/s.
文摘Heart rate variability （HRV） refers to the variations between consecutive heartbeats, which depend on the continuous modulation of the sympathetic and parasympathetic branches of the autonomic nervous system. HRV has been shown to be effective as a predictor of risk after myocardial infarction and an early warning sign of diabetic neuropathy, and in the cardiology setting is now recognized to be a useful tool for risk-stratification after hospital admission and after discharge. Recent evidences suggest that HRV analysis might predict complications even in patients undergoing cardiac surgery, and the present review summarizes the importance of HRV analysis in adult cardiac surgery and the perspectives for HRV use in current clinical practice. Although future larger studies are warranted before HRV can be included into daily clinical practice in adult cardiac surgery, HRV is a novel tool which might detect autonomic instability in the early postoperative phase and during hospital stay, thus predicting or prompt-diagnosing many of the post-operative complications.
文摘Objective A novel index based on fi-equency-domain analysis of heart rate variability （HRV） was tested on patients with reduced left ventricular systolic function. This index, namely VHFI, was defined as the very high frequency （VHF） component of the power spectrum normalized to represent its relative value in proportion to the total power minus the very low frequency component. Methods Patients （n = 130） were divided into a study group, consisting 66 patients with decreased left ventricular systolic function, and a control group, consisting 64 patients with normal heart structure and function and without severe coronary artery stenosis （〈 50%）. Results VHFI in the study group was significantly higher than that in the control group （19.17 ± 13.35 vs 11.37 ± 10.77, P 〈 0.001）. Cardiac events occurred in 18 patients during follow-up （33.34 i 3.26 months）. Defining the positive test as VHFI =15 and negative test as VHFI 〈15, achieved a sensitivity of 57.58% and a specificity of78.13% for predicting decreased left ventricular systolic function, and achieved a sensitivity of 66.67% and a specificity of 64.29% for predicting cardiac events. Univariate Cox regression analysis showed that positive VHFI test was an independent variable in predictive cardiac events. Conclusions The results suggest that VHFI is a useful tool for quick evaluation of left ventricular systolic function and prediction of prognosis
文摘Objective: To introduce a method to calculate cardiovascular age, a new, accurate and much simpler index for assessing cardiovascular autonomic regulatory function, based on statistical analysis of heart rate and blood pressure variability (HRV and BPV) and baroreflex sensitivity (BRS) data. Methods: Firstly, HRV and BPV of 89 healthy aviation personnel were analyzed by the conventional autoregressive (AR) spectral analysis and their spontaneous BRS was obtained by the sequence method. Secondly, principal component analysis was conducted over original and derived indices of HRV, BPV and BRS data and the relevant principal components, PCi orig and PCi deri (i=1, 2, 3,...) were obtained. Finally, the equation for calculating cardiovascular age was obtained by multiple regression with the chronological age being assigned as the dependent variable and the principal components significantly related to age as the regressors. Results: The first four principal components of original indices accounted for over 90% of total variance of the indices, so did the first three principal components of derived indices. So, these seven principal components could reflect the information of cardiovascular autonomic regulation which was embodied in the 17 indices of HRV, BPV and BRS exactly with a minimal loss of information. Of the seven principal components, PC2 orig , PC4 orig and PC2 deri were negatively correlated with the chronological age ( P <0 05), whereas the PC3 orig was positively correlated with the chronological age ( P <0 01). The cardiovascular age thus calculated from the regression equation was significantly correlated with the chronological age among the 89 aviation personnel ( r =0.73, P <0 01). Conclusion: The cardiovascular age calculated based on a multi variate analysis of HRV, BPV and BRS could be regarded as a comprehensive indicator reflecting the age dependency of autonomic regulation of cardiovascular system in healthy aviation personnel.
基金the National Natural Science Foundation of China(No.62301056)the Fundamental Research Funds for Central Universities(No.2022QN005).
文摘Moderate exercise contributes to health, but excessive exercise may lead to physicalinjury or even endanger life. It is pressing for a device that can detect the intensity of exercise.Therefore, in order to enable real-time detection of exercise intensity and mitigate the risks of harmfrom excessive exercise, a exercise intensity monitoring system based on the heart rate variability(HRV) from electrocardiogram (ECG) signal and linear features from phonocardiogram (PCG)signal is proposed. The main contributions include: First, accurate analysis of HRV is crucial forsubsequent exercise intensity detection. To enhance HRV analysis, we propose an R-peak detectorbased on encoder-decoder and temporal convolutional network (TCN). Experimental resultsdemonstrate that the proposed R-peak detector achieves an F1 score exceeding 0.99 on real high-intensity exercise ECG datasets. Second, an exercise fatigue monitoring system based on multi-signal feature fusion is proposed. Initially, utilizing the proposed R-peak detector for HRV extractionin exercise intensity detection,which outperforms traditional algorithms, with the system achieving a classification performance of 0.933 sensitivity, 0.802 specificity, and 0.960 accuracy. To further improve the system, we combine HRV with the linear features of PCG. Our exercise intensitydetection system achieves 90.2% specificity, 96.7% recall, and 98.1% accuracy in five-fold cross-validation.
文摘Objective: To elucidate the role of the autonomic nervous system (ANS) in acute mountain sickness (AMS) during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level residents rapidly ascended to Tibet plateau (3 675 m altitude) by airplane from Chengdu plain (560 m altitude). ANS function was tested in plain and day 2–4 in Tibet by heart rate variability (HRV), cold pressor test (CPT). AMS was evaluated by clinic symptomatic scores. All subjects were divided into non-AMS group (57, scores≤4) and AMS group (42, scores>4). Results: Compared with non-AMS group, AMS group had higher standard deviation of normal to normal intervals (SDNN), root mean square of delta RR (rMSSD), low-frequency (LF) power, and normalized low-frequency (LFnu) power in plain (P<0.05). After arrival at 3 675 m altitude, AMS group had greater reduction in percentage of delta RR>50 ms(PNN50), rMSSD (P<0.01) and SDNN, LF, total power (TP) (P<0.05). Although no significant differences in the increase of SP and DP during CPT were found between 2 groups in plain, the SP increase during CPT of AMS group was less than non-AMS group (P<0.05) at 3 675 m altitude. AMS symptomatic scores was not only positively correlated with SDNN, rMSSD, LF/HF in plain (P<0.05), but also negatively correlated with HFnu in plain (P<0.05). Conclusion: During the initial high altitude exposure, ANS modulation is generally blunted, but the relatively predominant sympathetic control is enhanced, and this characteristic change of ANS function is positively correlated with the development of AMS.
基金The primary support for this study was through the Joint Capability Technology Demonstration Program within the Office of the Under Secretary of Defense(Acquisition,Technology,and Logistics)via a contract with the U.S. Special Operations Commandsupported by a research grant from The Susanne Marcus Collins Foundation+1 种基金supported by NIBIB K25 EB012236-01A1support from the Office of the Assistant Secretar y of Defense for Health Affairs through the Psychological Health/Traumatic Brain Injury Research Program,Award No.W81XWH-17-2-0057
文摘Background:Military-related post-traumatic stress(PTS)is associated with numerous symptom clusters and diminished autonomic cardiovascular regulation.Highresolution,relational,resonance-based,electroencephalic mirroringis a noninvasive,closed-loop,allostatic,acoustic stimulation neurotechnology that produces realtime translation of dominant brain frequencies into audible tones of variable pitch and timing to support the autocalibration of neural oscillations.We report clinical,autonomic,and functional effects after the use offor symptoms of military-related PTS.Methods:Eighteen service members or recent veterans(15 active-duty,3 veterans,most from special operations,1 female),with a mean age of 40.9(SD=6.9)years and symptoms of PTS lasting from 1 to 25 years,undertook19.5(SD=1.1)sessions over 12 days.Inventories for symptoms of PTS(Posttraumatic Stress Disorder Checklist–Military version,PCL-M),insomnia(Insomnia Severity Index,ISI),depression(Center for Epidemiologic Studies Depression Scale,CES-D),and anxiety(Generalized Anxiety Disorder 7-item scale,GAD-7)were collected before(Visit1,V1),immediately after(Visit2,V2),and at 1 month(Visit3,V3),3(Visit4,V4),and 6(Visit5,V5)months after intervention completion.Other measures only taken at V1 and V2 included blood pressure and heart rate recordings to analyze heart rate variability(HRV)and baroreflex sensitivity(BRS),functional performance(reaction and grip strength)testing,blood and saliva for biomarkers of stress and inflammation,and blood for epigenetic testing.Paired t-tests,Wilcoxon signed-rank tests,and a repeated-measures ANOVA were performed.Results:Clinically relevant,significant reductions in all symptom scores were observed at V2,with durability through V5.There were significant improvements in multiple measures of HRV and BRS[Standard deviation of the normal beat to normal beat interval(SDNN),root mean square of the successive differences(rMSSD),high frequency(HF),low frequency(LF),and total power,HF alpha,sequence all,and systolic,diastolic and mean arterial pressure]as well as reaction testing.Trends were seen for improved grip strength and a reduction in C-Reactive Protein(CRP),Angiotensin II to Angiotensin 1–7 ratio and Interleukin-10,with no change in DNA n-methylation.There were no dropouts or adverse events reported. Conclusion:Service members or veterans showed reductions in symptomatology of PTS,insomnia,depressive mood,and anxiety that were durable through 6 months after the use of a closed-loop allostatic neurotechnology for the autocalibration of neural oscillations.This study is the first to report increased HRV or BRS after the use of an intervention for service members or veterans with PTS.Ongoing investigations are strongly warranted.Trial registration:NCT03230890,retrospectively registered July 25,2017.
文摘Objective: To investigate the changes of autonomic nervous system (ANS) function during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level male residents were studied in Chengdu plain and then Tibet plateau. Heart rate variability (HRV), cold pressor test (CPT), resting heart rate (HR) and blood pressure (BP) were measured at baseline (560 m altitude) and in 2 to 4 d after arriving at Tibet plateau (3 675 m altitude) to assess the ANS function. Results: Compared with baseline, on day 2 in Tibet the standard deviation of normal to normal intervals (SDNN), high-frequency (HF) power, total power (TP), root mean square of delta RR (rMSSD), percentage of delta RR>50 ms (PNN50), normalized high-frequency (HFnu) and fractal dimension (FD) decreased significantly (SDNN, HF, TP P<0.01, rMSSD, PNN50, HFnu, FD P<0.05), while the normalized low-frequency (LFnu) and LF/HF increased significantly (P<0.01). During day 3–4 in Tibet, SDNN, rMSSD, HF, TP and HFnu tended to rebound while LFnu and LF/HF decreased towards baseline day by day. In addition, in Tibet the increase in systolic pressure (SP) and diastolic pressure (DP) during CPT decreased significantly (P<0.01, 0.05), but resting HR increased compared with baseline (P<0.01). Conclusion: ANS modulation is generally blunted, and the relatively predominant sympathetic control is enhanced originally, then it reverts to the sea level states gradually during the initial days of acute high-altitude exposure.
