Entropy Analysis of Univariate Biomedical Signals:Review and Comparison of Methods

International audienc

Entropía aproximada y muestral de la variabilidad de la frecuencia cardíaca en electrocardiogramas cortos y largos de hombres jóvenes

El objetivo del estudio fue evaluar las diferencias de la entropía aproximada (ApEn) y la entropía muestral (SampEn) de la variabilidad de la frecuencia cardíaca (HRV) entre registros electrocardiográficos (ECG) de distinta duración. Para esto, se compararon las medidas de la ApEn y la SampEn obtenidas a partir de electrocardiogramas de 3, 5 y 15 minutos de duración de hombres jóvenes, entre los 18 y los 25 años, residentes en la ciudad de Cúcuta. Los ECG se tomaron con el sistema de adquisición de datos Powerlab 26T/LabChart Pro de ADInstrumentsTM, el cual se programó para medir los intervalos RR. Posteriormente, estos valores se introdujeron a Kubios, un software de análisis de la HRV, que calculó la ApEn y la SampEn de cada registro. La prueba de hipótesis no paramétrica de Friedman reportó, con un nivel de confianza del 95%, que la ApEn presenta diferencias significativas entre los ECG comparados valor p=0,00, mientras que la SampEn no presenta diferencias entre estos grupos valor p=0,311. Asimismo, comparaciones dos a dos entre cada par de ECG, mediante la prueba de Wilcoxon de dos muestras relacionadas, permitieron concluir, con un nivel de confianza mayor al 98% por el ajuste de Bonferroni, que la ApEn presenta diferencias estadísticamente significativas entre cada uno de los ECG. De este modo, se puede afirmar que la ApEn de la HRV es muy sensible a la duración del ECG, presentado diferencias significativas entre registros cortos y largos, mientras que la SampEn muestra mayor consistencia.Abstract. The objective of the study was to assess the differences in approximate entropy (ApEn) and sample entropy (SampEn) of heart rate variability (HRV) between electrocardiograms (ECG) of different duration. For this, the measures of ApEn and SampEn obtained from ECGs of 3, 5 and 15 minutes of young men between the ages of 18 and 25 residing in the city of Cúcuta were compared. ECGs were recorded with the data acquisition system Powerlab 26T/LabChart Pro, which was programmed to measure RR intervals. Subsequently, these values were introduced to Kubios, HRV analysis software, which calculated the ApEn and SampEn of each ECG. Nonparametric Friedman's test stated at the 95% confidence level reported that ApEn presented significant differences between ECGs compared (p value = 0.00), whereas the SampEn showed no difference between these groups P = 0.311). Likewise, comparisons between each pair of electrocardiograms, using wilcoxon test for two related samples, reported that ApEn presented statistically significant differences between each one of ECGs, confidence level higher than 98% by the Bonferroni adjustment. Thus, it can be affirmed that ApEn of the HRV is very sensitive to the duration of the ECG and present significant differences between short and long electrocardiograms, whereas the SampEn shows greater consistency.Maestrí

Effect of data length and bin numbers on distribution entropy (DistEn) measurement in analyzing healthy aging

Complexity analysis of a given time series is executed using various measures of irregularity, the most commonly used being Approximate entropy (ApEn), Sample entropy (SampEn) and Fuzzy entropy (FuzzyEn). However, the dependence of these measures on the critical parameter of tolerance `r\u27 leads to precarious results, owing to random selections of r. Attempts to eliminate the use of r in entropy calculations introduced a new measure of entropy namely distribution entropy (DistEn) based on the empirical probability distribution function (ePDF). DistEn completely avoids the use of a variance dependent parameter like r and replaces it by a parameter M, which corresponds to the number of bins used in the histogram to calculate it. When tested for synthetic data, M has been observed to produce a minimal effect on DistEn as compared to the effect of r on other entropy measures. Also, DistEn is said to be relatively stable with data length (N) variations, as far as synthetic data is concerned. However, these claims have not been analyzed for physiological data. Our study evaluates the effect of data length N and bin number M on the performance of DistEn using both synthetic and physiologic time series data. Synthetic logistic data of `Periodic\u27 and `Chaotic\u27 levels of complexity and 40 RR interval time series belonging to two groups of healthy aging population (young and elderly) have been used for the analysis. The stability and consistency of DistEn as a complexity measure as well as a classifier have been studied. Experiments prove that the parameters N and M are more influential in deciding the efficacy of DistEn performance in the case of physiologic data than synthetic data. Therefore, a generalized random selection of M for a given data length N may not always be an appropriate combination to yield good performance of DistEn for physiologic data

Muscle activation patterns in shoulder impingement patients

Introduction: Shoulder impingement is one of the most common presentations of shoulder joint problems 1. It appears to be caused by a reduction in the sub-acromial space as the humerus abducts between 60o -120o – the 'painful arc'. Structures between the humeral head and the acromion are thus pinched causing pain and further pathology 2. Shoulder muscle activity can influence this joint space but it is unclear whether this is a cause or effect in impingement patients. This study aimed to observe muscle activation patterns in normal and impingement shoulder patients and determine if there were any significant differences. Method: 19 adult subjects were asked to perform shoulder abduction in their symptomatic arm and non-symptomatic. 10 of these subjects (age 47.9 ± 11.2) were screened for shoulder impingement, and 9 subjects (age 38.9 ± 14.3) had no history of shoulder pathology. Surface EMG was used to collect data for 6 shoulder muscles (Upper, middle and lower trapezius, serratus anterior, infraspinatus, middle deltoids) which was then filtered and fully rectified. Subjects performed 3 smooth unilateral abduction movements at a cadence of 16 beats of a metronome set at 60bpm, and the mean of their results was recorded. T-tests were used to indicate any statistical significance in the data sets. Significance was set at P<0.05. Results: There was a significant difference in muscle activation with serratus anterior in particular showing a very low level of activation throughout the range when compared to normal shoulder activation patterns (<30%). Middle deltoid recruitment was significantly reduced between 60-90o in the impingement group (30:58%).Trends were noted in other muscles with upper trapezius and infraspinatus activating more rapidly and erratically (63:25%; 60:27% respectively), and lower trapezius with less recruitment (13:30%) in the patient group, although these did not quite reach significance. Conclusion: There appears to be some interesting alterations in muscle recruitment patterns in impingement shoulder patients when compared against their own unaffected shoulders and the control group. In particular changes in scapula control (serratus anterior and trapezius) and lateral rotation (infraspinatus), which have direct influence on the sub-acromial space, should be noted. It is still not clear whether these alterations are causative or reactionary, but this finding gives a clear indication to the importance of addressing muscle reeducation as part of a rehabilitation programme in shoulder impingement patients

Друга міжнародна конференція зі сталого майбутнього: екологічні, технологічні, соціальні та економічні питання (ICSF 2021). Кривий Ріг, Україна, 19-21 травня 2021 року

Second International Conference on Sustainable Futures: Environmental, Technological, Social and Economic Matters (ICSF 2021). Kryvyi Rih, Ukraine, May 19-21, 2021.Друга міжнародна конференція зі сталого майбутнього: екологічні, технологічні, соціальні та економічні питання (ICSF 2021). Кривий Ріг, Україна, 19-21 травня 2021 року