MODELING TREND AND TIME-VARYING VARIANCE OF HEART BEAT RR INTERVALS DURING STRESS TEST

2011 ◽  
Vol 10 (02) ◽  
pp. 169-180 ◽  
Author(s):  
CAMILLO CAMMAROTA ◽  
MARIO CURIONE
Keyword(s):  
Global Minimum ◽  
Stress Test ◽  
Heart Beat ◽  
Random Fluctuation ◽  
Data Series ◽  
Time Varying ◽  
Rr Intervals ◽  
Deterministic Trend ◽  
Increasing Trend ◽  
Mean Reverting Process

The heart beat RR intervals extracted from the electrocardiogram recorded during the stress test show a non stationary profile consisting of a decreasing trend during the exercise phase, an increasing trend during the recovery and a global minimum (acme). In addition this time series exhibits a time-varying variance. We decompose the series into a deterministic trend and random fluctuation. The trend is obtained as an exponential fit of the data; the fluctuation is modeled as a mean reverting process driven by the trend, in which the random innovation has a time-varying variance. Data analysis, performed on ambulatory recorded electrocardiograms of 10 healthy subjects, shows that the model describes correctly the data series on a scale of at least 300 beats.

scholarly journals Coupling of autonomic and central events during sleep benefits declarative memory consolidation

2017 ◽  
Author(s):  
Mohsen Naji ◽  
Giri P. Krishnan ◽  
Elizabeth A McDevitt ◽  
Maxim Bazhenov ◽  
Sara C. Mednick
Keyword(s):  
Memory Consolidation ◽  
Declarative Memory ◽  
Memory Performance ◽  
Memory Task ◽  
Nrem Sleep ◽  
Heart Beat ◽  
Vagal Activity ◽  
Rr Intervals ◽  
Slow Oscillations ◽  
Event Based

AbstractWhile anatomical pathways between forebrain cognitive and brainstem autonomic nervous centers are well defined, autonomic–central interactions during sleep and their contribution to waking performance are not understood. Here, we analyzed simultaneous central activity via electroencephalography (EEG) and autonomic heart beat-to-beat intervals (RR intervals) from electrocardiography (ECG) during wake and daytime sleep. We identified bursts of ECG activity that lasted 4-5 seconds and predominated in non-rapid-eye-movement sleep (NREM). Using event-based analysis of NREM sleep, we found an increase in delta (0.5-4Hz) and sigma (12-15Hz) power and an elevated density of slow oscillations (0.5-1Hz) about 5 secs prior to peak of the heart rate burst, as well as a surge in vagal activity, assessed by high-frequency (HF) component of RR intervals. Using regression framework, we show that these Autonomic/Central Events (ACE) positively predicted post-nap improvement in a declarative memory task after controlling for the effects of spindles and slow oscillations from sleep periods without ACE. No such relation was found between memory performance and a control nap. Additionally, NREM ACE negatively correlated with REM sleep and learning in a non-declarative memory task. These results provide the first evidence that coordinated autonomic and central events play a significant role in declarative memory consolidation.

scholarly journals Quasi-1500-Year-Cycle Signal in Length-of-Day Change

2021 ◽  
Vol 56 (2) ◽  
pp. 10-17
Author(s):  
Lihua MA
Keyword(s):  
Rotation Rate ◽  
Time Span ◽  
Historical Documents ◽  
Data Series ◽  
Earth’S Rotation ◽  
Time Varying ◽  
Length Of Day ◽  
The Past ◽  
Continuous Sequence

Abstract Length-of-day (LOD) change, i.e., variations in Earth’s rotation rate, includes the long-term slowdown trend, as well as periodic and irregular fluctuations. The current continuous sequence of the LOD change covers a time span of <400 years. Using astronomical records in ancient historical documents, combined with a modern astronomical ephemeris, it is possible to obtain ancient LOD change. Some scholars have given a discontinuous LOD data series for the past 4000 years. In this paper, the author uses the Lomb–Scargle periodogram to study the LOD series and finds a significant quasi-1500-year-cycle signal. Furthermore, with weighted wavelet Z-transform, time-varying characteristics of the cycle in the LOD change are obtained.

scholarly journals Biophysical profile and modified biophysical profile in predicting the fetal outcome

2018 ◽  
Vol 7 (9) ◽  
pp. 3516
Author(s):  
V. G. Vanamala ◽  
Aruna Rachel ◽  
Sushil Pakyanadhan ◽  
Sudheep Abraham P.
Keyword(s):  
Amniotic Fluid ◽  
Stress Test ◽  
Well Being ◽  
Fetal Outcome ◽  
Heart Beat ◽  
Amniotic Fluid Index ◽  
Uterine Contractions ◽  
Beat Pattern ◽  
Biophysical Profile ◽  
Fetal Movements

Background: Baby’s well-being in utero is often done by using a cardiotocograph (CTG) machine, which assesses the baby’s heart beat pattern as well as the mother’s uterine contractions. However, lowered fetal movements sometimes may be fatal for the baby. Thus, the biophysical and the modified biophysical profile have been introduced.Methods: 242 patients with over 34 weeks of gestation and with one or more risk factors were included in the study. After taking the demographic details, the patients were subjected to detailed physical and clinical evaluation. Modified BPP was done on all the patients. Index of acute fetal hypoxia the NST was done along with the cardiotocograph (CTG). Amniotic fluid volume was calculated.Results: According to the fetal non-stress test, majority of the patients (70.7%) were reactive while 29.3% were non-reactive. Most of the patients had an amniotic fluid index in the normal range i.e. between 8 -<25, 18.6%) had an AFI value of <6 cm while 13.6% had between 6 - <8. Among the babies with reactive NST, non-reactive NST and AFI ≤5, the most common outcome was low birth weight.  APGAR score <7 was observed in 11.1%, 13.1%, 20% among Reactive NST, Non-reactive NST and AFI ≤5 respectively.Conclusions: Present study shows that BPP and MBPP are both comparable to each other, therefore, MBPP, being an easier test can be substituted for BPP.

scholarly journals Spatio-Temporal Trends and Variability of Temperature Over Bale Zone, Ethiopia

2019 ◽  
Vol 9 (2) ◽  
pp. 903-916
Keyword(s):  
Minimum Temperature ◽  
Temporal Trends ◽  
Temperature Series ◽  
Spatiotemporal Variability ◽  
Maximum Temperature ◽  
Data Series ◽  
Parametric Test ◽  
Temperature Trends ◽  
Increasing Trend ◽  
Bale Zone

Understanding of temperature trends and their spatiotemporal variability has great significances on making deep insight for planners, managers, professionals and decision makers of water resources and agriculture. Therefore, this research was set with aim to analyze spatiotemporal variability of temperature and their time series trends over Bale Zone. Statistical analysis: Parametric test with regression analysis on the anomalies like deviation from mean and Non-parametric test with Mann-Kendall test together with Sen’s Slope Estimator & Zs statistics has been used for estimation of trends of a historical data series of monthly, seasonal and annually maximum and minimum temperature of selected meteorological stations in Bale Zone. Both tests relatively shows same results for monthly, seasonal and yearly temperature series. The coefficient of variation (CV) was used for variability analysis. Arc GIS 9.3 software was also used to investigate the spatial variability temperature (minimum and maximum) for the period under review. These methodology has shown a significant increasing and decreasing trends at 95% confidence level for certain time scale temperature series: temperature trends (i.e the mean maximum temperature series) showed a significant increasing trend in Robe (Annual, Spring, February, March, April, May, July, and October), Ginir (February, July, September, and December).Mean minimum temperature series showed a substantial increasing trend in Robe (May, July, September, and November) and Hunte (September). It is also observed that Mean seasonal and annually minimum temperature of the stations have shown higher variability than those mean seasonal and annual maximum temperature of the stations.

scholarly journals Spatio -Temporal Assessments of Rainfall Variability and Trends in the Highlands to Coastal Regions of Papua New Guinea

2021 ◽  
pp. 23-38
Author(s):  
T. Sekac ◽  
S.K. Jana ◽  
M. Sutherland ◽  
S. Samanta
Keyword(s):  
Rainfall Variability ◽  
Data Series ◽  
Coastal Zones ◽  
Rainfall Trends ◽  
Increasing Trend ◽  
Sen’S Method ◽  
Seasonal Basis ◽  
Study Zone ◽  
Spatio Temporal ◽  
Spatial Investigation

The present study assesses spatio-temporal rainfall variability of the most highlands to the coastal zones, comprising of eight provinces, of PNG. The variability investigation was carried out over for a period of 50 years starting from the year 1968 to 2018. After testing and checking for serial autocorrelation in the data series, Mann-Kendal non-parametric statistical evaluation was carried out to investigate rainfall trends and variability. Sen’s method was also used to investigate the magnitude of change in millimeters (mm) per year. Furthermore, the ArcGIS spatial analysis tools were used for the calculation of mean rainfall and to carry out spatial investigation. The assessments were carried out on an annual and seasonal basis within each designated study zone. CRU TS 4.03 gridded rainfall data on a 0.50 x 0.50 spatial resolution was used as an input data for trend as well as variability investigation. The CRU gridded station wise analysis was carried out to understand the variability at each specific location. From the assessments, it was found out that a higher rainfall is observed in the Eastern parts of Morobe, Southern Highlands region and central to northern part of Madang Province, while a low rainfall was observed in Goroka, the Western part of Morobe, Simbu, Western Highlands, Jiwaka and Enga province. From the trend investigation, it was observed that more grid stations show an increasing trend than a decreasing trend. On annual assessments, the significant decreasing trend is observed in the Enga and SH province, while significantly increasing trend is observed in the whole parts of Madang, and to the northern part of EH and Simbu Province. From overall assessments, it was found out that, there has been an increasing trend since 1968 up to the present.

Design and Validation of a Low-Cost Heart Health Monitoring Device

2018 ◽  
Author(s):  
Nuzhat Ahmed ◽  
Lucas Kline ◽  
Yong Zhu
Keyword(s):  
Heart Rate ◽  
Health Monitoring ◽  
Information Technologies ◽  
Low Cost ◽  
Heart Beat ◽  
Heart Health ◽  
Cardiac Events ◽  
Rr Intervals ◽  
Time Period ◽  
Normal Heart Rate

The heart health monitoring system is a combination of electronics, wireless communication, computer, and information technologies, which allows an individual to measure and analyze their heart rate in real time and also notifies them about any abnormal cardiac events. This project was performed with an objective of developing and validating a low-cost, portable system that will successfully detect symptomless Atrial Fibrillation (AF), which is considered to be one of the most common and frequent cardiac disorders. The prototype device will measure and analyze the heart beat variations and varying-time period between successive R peaks (RR intervals) of the ECG signal and will compare the results with the normal heart rate and RR intervals. Upon exceeding the threshold values, this device will create an alert to notify about the potential AF detection.

scholarly journals Asymmetric properties of heart rate microstructure

2020 ◽  
Vol 89 (2) ◽  
pp. e436
Author(s):  
Przemysław Guzik ◽  
Jarosław Piskorski
Keyword(s):  
Myocardial Infarction ◽  
Heart Rate ◽  
Predictive Value ◽  
Stress Test ◽  
Total Mortality ◽  
Rr Intervals ◽  
Obstructive Sleep ◽  
Exercise Treadmill ◽  
Acceleration And Deceleration ◽  
Clinical Conditions

The duration of each cardiac cycle is measured on ECG as the distance between the peaks of consecutive R waves (RR interval). Its inverse value corresponds to the heart rate (HR) changing in a beat-to-beat manner. HR accelerations are reflected as the shortenings of RR intervals while HR decelerations as the lengthening of RR intervals. HR asymmetry is a physiological phenomenon caused by an unequal input of HR decelerations and accelerations to the HR variability. Naturally occurring consecutive values of RR intervals create time series which are composed of acceleration and deceleration runs of different length. Some examples are a single HR acceleration, a pair of HR decelerations, a run consisting of five consecutive HR decelerations or a run composed of eight accelerations in a row. These runs make up the so-called heart rate microstructure that has asymmetric properties due to unequal contribution of acceleration and deceleration runs. Asymmetry of HR microstructure is a physiological finding in healthy people. However, the asymmetric properties of HR microstructure have been shown to significantly alter in some clinical conditions such as myocardial infarction, obstructive sleep apnea, chronic obturatory pulmonary disease or sepsis in infants. An abnormal HR microstructure has predictive value in survivors of myocardial infarction or patients with clinical indications for exercise treadmill stress test, e.g., for total mortality. In this review, we present and explain how the asymmetric properties of HR microstructure can be quantified, and summarise available data on the clinical and predictive value of this phenomenon and its analysis.

scholarly journals Credibility Models with Time-Varying Trend Components

1991 ◽  
Vol 21 (1) ◽  
pp. 73-91 ◽  
Author(s):  
Johannes Ledolter ◽  
Stuart Klugman ◽  
Chang-Soo Lee
Keyword(s):  
Automobile Insurance ◽  
Time Varying ◽  
Ample Evidence ◽  
Varying Parameters ◽  
Deterministic Trend ◽  
Time Varying Parameters ◽  
Over Time

AbstractTraditional credibility models have treated the process generating the losses as stable over time, perhaps with a deterministic trend imposed. However, there is ample evidence that these processes are not stable over time. What is required is a method that allows for time-varying parameters in the process, yet still provides the shrinkage needed for sound ratemaking. In this paper we use an automobile insurance example to illustrate how this can be accomplished.

TIME DELAY BETWEEN RR AND RT HEART BEAT INTERVALS ASSESSED BY TREND EXTRACTION OF EXERCISE TEST DATA

2012 ◽  
Vol 11 (04) ◽  
pp. 1250019 ◽  
Author(s):  
CAMILLO CAMMAROTA ◽  
MARIO CURIONE
Keyword(s):  
Time Delay ◽  
Exercise Test ◽  
Heart Beat ◽  
Time Intervals ◽  
Multi Scale ◽  
Trend Extraction ◽  
Polynomial Fit ◽  
Deterministic Trend ◽  
Trend Data ◽  
Random Fluctuations

The RR and RT time intervals extracted from the electrocardiogram measure respectively the duration of cardiac cycle and repolarization. The series of these intervals recorded during the exercise test are characterized by two trends: A decreasing one during the stress phase and an increasing one during the recovery, separated by a global minimum. We model these series as a sum of a deterministic trend and random fluctuations, and estimate the trend using methods of curve extraction: Running mean, polynomial fit, multi scale wavelet decomposition. We estimate the minimum location from the trend. Data analysis performed on a group of 20 healthy subjects provides evidence that the minimum of the RR series precedes the minimum of the RT series, with a time delay of about 19 seconds.

scholarly journals Extreme rainfall trends over the Mekong Delta under the impacts of climate change

2020 ◽  
Vol 12 (5) ◽  
pp. 639-652 ◽  
Author(s):  
Seung Kyu LEE ◽  
Truong An Dang
Keyword(s):  
Heavy Rainfall ◽  
Mekong Delta ◽  
Kendall Test ◽  
Data Series ◽  
Entire Study ◽  
Content Type ◽  
Slope Estimate ◽  
Increasing Trend ◽  
Entire Study Area

Purpose This study aims to investigate aspects related to the changing trends of the rainfall extremes in the entire Mekong Delta in the period of 32 years (1984-2015) applying rainfall extreme indices. First, the homogeneity tests were applied to assess the quality of observed rainfall data series. The authors, then, investigated three rainfall indices including the number of very heavy rainfall days 20 mm (R20), number of days above 50 mm (R50) and number of days above 100 mm (R100) applying the Mann-Kendall test and Sen’s slope estimate. Design/methodology/approach First, the homogeneity tests were applied to assess the quality of observed rainfall data series. The authors, then, investigated three rainfall indices including the number of very heavy rainfall days 20 mm (R20), number of days above 50 mm (R50) and number of days above 100 mm (R100) applying the Mann-Kendall test and Sen’s slope estimate. Findings The results of R20 pointed out that an insignificant upward tendency was found in the coastal provinces, whereas an insignificant downward tendency was also recorded in the inland provinces. Regarding the number of R50, a similar trend to R20 was recorded with five stations slightly increased and five stations slightly decreased. For the number of R100, the results recorded an absence of significant trends over the entire study area. Approximately 58.5% of stations show a slightly decreasing trend, while 41.5% of the remaining stations recorded a slightly increasing trend. Originality/value For the number of R100, the results recorded an absence of the significant trends over the entire study area. Approximately 58.5% of stations show a slightly decreasing trend, while 41.5% of the remaining stations recorded a slightly increasing trend. Of note is the fact that the number of R100 occurred more frequently in the northern provinces, which means the northern region is facing a high risk of flooding.

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