1,721,037 research outputs found
Cepstral Analysis for Scoring the Quality of Electrocardiograms for Heart Rate Variability
Full text linkMobile-health solutions based on heart rate variability often require electrocardiogram (ECG) recordings by inexperienced operators or real-time automatic analyses of long-term recordings by wearable devices in free-moving individuals. In this context, it is useful to associate a quality index with the ECG, scoring the adequacy of the recording for heart rate variability to identify noise or arrhythmias. Therefore, this work aims to propose and validate a computational method for assessing the adequacy of single-lead ECGs for heart rate variability analysis that may run in real time on wearable systems with low computational power. The method quantifies the ECG pseudo-periodic structure employing cepstral analysis. The cepstrum (spectrum of log-spectrum) is estimated on a running ECG window of 10 s before and after “liftering” (filtering in the cepstral domain) to remove slower noise components. The ECG periodicity generates a dominant peak in the liftered cepstrum at the “quefrency” of the mean cardiac interval. The Cepstral Quality Index (CQI) is the ratio between the cepstral-peak power and the total power of the unliftered cepstrum. Noises and arrhythmias reduce the relative power of the cepstral peak decreasing CQI. We analyzed a public dataset of 6072 single-lead ECGs manually classified in normal rhythm or inadequate for heart rate variability analysis because of noise or atrial fibrillation, and the CQI = 47% cut-off identified the inadequate recordings with 79% sensitivity and 85% specificity. We showed that the performance is independent of the lead considering a public dataset of 1,000 12-lead recordings with quality classified as “acceptable” or “unacceptable” by visual inspection. Thus, the cepstrum describes the ECG periodic structure effectively and concisely and CQI appears to be a robust score of the adequacy of ECG recording for heart rate variability analysis, evaluable in real-time on wearable devices
Multiscale assessment of the degree of multifractality for physiological time series
No full textRecent advancements in detrended fluctuation analysis (DFA) allow evaluating multifractal coefficients scale-by-scale, a promising approach for assessing the complexity of biomedical signals. The multifractality degree is typically quantified by the singularity spectrum width (W SS), a method that is critically unstable in multiscale applications. Thus, we aim to propose a robust multiscale index of multifractality, compare it with W SS and illustrate its performance on real biosignals. The proposed index is the cumulative function of squared increments between consecutive DFA coefficients at each scale n: α CF (n). We compared it with W SS calculated scale-by-scale considering monofractal/monoscale, monofractal/multiscale, multifractal/monoscale and multifractal/multiscale random processes. The two indices provided qualitatively similar descriptions of multifractality, but α CF (n) differentiated better the multifractal components from artefacts due to crossovers or detrending overfitting. Applied on 24 h heart rate recordings of 14 participants, the singularity spectrum failed to always satisfy the concavity requirement for providing meaningful W SS, while α CF (n) demonstrated a statistically significant heart rate multifractality at night in the scale ranges 16-100 and 256-680 s. Furthermore, α CF (n) did not reject the hypothesis of monofractality at daytime, coherently with previous reports of lower nonlinearity and monoscale multifractality during the day. Thus, α CF (n) appears a robust index of multiscale multifractality that is useful for quantifying complexity alterations of physiological series. This article is part of the theme issue 'Advanced computation in cardiovascular physiology: new challenges and opportunities'
Comment on “Modified multiscale fuzzy entropy: A robust method for short-term physiologic signals” [Chaos 30, 083135 (2020)]
No full textFractal analysis of heart rate variability reveals alterations of the integrative autonomic control of circulation in paraplegic individuals
Full text linkThe autonomic nervous system plays a major role in the integrative control of circulation, possibly contributing to the 'complex' dynamics responsible for fractal components in heart rate variability. Aim of this study is to evaluate whether an altered autonomic integrative control is identified by fractal analysis of heart rate variability. We enrolled 14 spinal cord injured individuals with complete lesion between the 5th and 11th thoracic vertebra (SCIH), 14 with complete lesion between 12th thoracic and 5th lumbar vertebra (SCIL), and 34 able-bodied controls (AB). These paraplegic subjects have an altered autonomic integrative regulation, but intact autonomic cardiac control and, as to SCILindividuals, intact autonomic splanchnic control. Power spectral and fractal analysis (temporal spectrum of scale coefficients) were performed on 10 min tachograms. AB and SCILpower spectra were similar, while the SCILfractal spectrum had higher coefficients between 12 and 48 s. SCIHindividuals had lower power than controls at 0.1 Hz; their fractal spectrum was morphologically different, diverging from that of controls at the largest scales (120 s). Therefore, when the lesion compromises the autonomic control of lower districts, fractal analysis reveals alterations undetected by power spectral analysis of heart rate variability
Complexity in Heart Rate Variability after Postural Sympathovagal Change by Sample, Fuzzy, and Distribution Entropy
No full textDistribution Entropy (DistEn) has been proposed to quantify the heart rate variability (HRV) complexity as an alternative to Sample (SampEn) or Fuzzy (FuzzyEn) entropies, which essentially measure the HRV randomness. We aim to evaluate if postural sympathovagal activations in healthy individuals induce changes in HRV complexity or randomness by jointly estimating DistEn, SampEn, and FuzzyEn. We compared the estimators on white, pink, and random noises, and on chaotic and periodic series. Then, we considered supine (Sup) and sitting (Sit) heart-rate recordings of 34 volunteers comparing SampEn, FuzzyEn, and DistEn between postures. Synthesized series highlighted the different nature of the estimators, being the highest entropy that of white noise for SampEn and FuzzyEn, that of the chaotic series for DistEn. SampEn and FuzzyEn of real heart rate series were greater in Sup, while DistEn did not differ between postures. Thus, the postural change does not change the HRV complexity as quantified by DistEn and DistEn is not an index of sympathovagal balance, unlike SampEn or FuzzyEn
Three-wavelength SPAD-based photoplethysmography
No full textContinuous and real-time monitoring of cardiorespiratory signals by portable and accurate instrumentation is very important for the early diagnosis of cardiovascular diseases. We aim to present a novel photoplethysmography device to assess changes in blood oxygen saturation and beat-bybeat pulse waves of finger blood volumes not affected by possibly occurring variations in oxygen saturation. For this purpose, our device works at three light wavelengths simultaneously and is based on a Single-Photon Avalanche Diode to evaluate the feasibility of using this technology in contact photoplethysmography. Our preliminary validation shows that the device is robust against movement artifacts and provides measures that reflect the physiological cardiorespiratory adaptations to the Valsalva maneuver, suggesting its overall reliability and possible use in cardiovascular monitoring
Respiratory patterns and baroreflex function in heart failure
Full text linkLittle is known on the effects of respiratory patterns on baroreflex function in heart failure (HF). Patients with HF (n = 30, age 61.6 ± 10 years, mean ± SD) and healthy controls (CNT, n = 10, age 58.9 ± 5.6 years) having their R-R interval (RRI, EKG), systolic arterial blood pressure (SBP, Finapres) and respiratory signal (RSP, Respitrace) monitored, were subjected to three recording sessions: free-breathing, fast- (≥ 12 bpm) and slow- (6 bpm) paced breathing. Baroreflex sensitivity (BRS) and power spectra of RRI, SBP, and RSP signals were calculated. During free-breathing, compared to CNT, HF patients showed a significantly greater modulation of respiratory volumes in the very-low-frequency (< 0.04 Hz) range and their BRS was not significantly different from that of CNT. During fast-paced breathing, when very-low-frequency modulations of respiration were reduced, BRS of HF patients was significantly lower than that of CNT and lower than during free breathing. During slow-paced breathing, BRS became again significantly higher than during fast breathing. In conclusion: (1) in free-breathing HF patients is present a greater modulation of respiratory volumes in the very-low-frequency range; (2) in HF patients modulation of respiration in the very-low and low frequency (around 0.1 Hz) ranges contributes to preserve baroreflex-mediated control of heart rate
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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