Usually, the respiratory frequency during heart rate variability studies is roughly controlled via the metronome sound to keep the respiratory sinus arrhythmia as fixed as possible. Besides a shortage of information, contradictory results... more
Usually, the respiratory frequency during heart rate variability studies is roughly controlled via the metronome sound to keep the respiratory sinus arrhythmia as fixed as possible. Besides a shortage of information, contradictory results about the reproducibility of the respiratory sinus arrhythmia have been reported. Thus, we propose a new electronic device to improve the respiratory sinus arrhythmia reproducibility through a close control of the respiratory rhythm. The device, based on a microcontroller and a column of 60 LED’s display, shows the desired rhythm to be followed by the subject. The instrument was tested three alternate days in 11 healthy subjects breaRevista Mexicana de Ingenieria Biomedica • volumen XXII • numero 2 • Septiembre 2001 62
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INTRODUCTION: The first hours of life are still a window of opportunity to identify at-risk newborns, but there are few studies focusing on early neonatal behavior.OBJECTIVE: Describe in a cross section the behavior of newborns born in... more
INTRODUCTION: The first hours of life are still a window of opportunity to identify at-risk newborns, but there are few studies focusing on early neonatal behavior.OBJECTIVE: Describe in a cross section the behavior of newborns born in conditions of low perinatal risk under 48 hours of extrauterine life and compare it with historical referents.METHOD: We studied 47 newborns with low perinatal risk, whose behavior was assessed using the Brazelton Neonatal Behavioral Assessment Scale (NBAS). Scores were obtained by item and area, and then were compared with 7 historical referents.RESULTS: Low scores were found, both by item and by areas in up to 25% of the population. NBAS scores were related primarily with age of newborn, weight, and height. Significant differences were found in relation to referents for which higher scores were reported in the majority of cases.CONCLUSIONS: A pattern was found of behavior, in which the same areas or items caused greater or lesser difficulty in achie...
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Pulmonary auscultation with traditional stethoscope, although useful, has limitations for detecting discontinuous adventitious respiratory sounds (crackles) that commonly occur in respiratory diseases. In this work, we present the... more
Pulmonary auscultation with traditional stethoscope, although useful, has limitations for detecting discontinuous adventitious respiratory sounds (crackles) that commonly occur in respiratory diseases. In this work, we present the development of a mobile health system for the automated detection of crackle sounds, comprised by an acoustical sensor, a smart phone device, and a mobile application (app) implemented in Android. The app allows the physician to record, store, reproduce, and analyze respiratory sounds directly on the smart phone. The algorithm for crackle detection was based on a time-varying autoregressive modeling. Performance of the automated detector was analyzed using synthetic fine and coarse crackle sounds randomly added to the basal respiratory sounds acquired from healthy subjects with different signal to noise ratios. Accuracy and sensitivity were found to range from 90.7% to 94.0% and from 91.2% to 94.2%, respectively. Application of the proposed mobile system t...
Research Interests: Algorithms, Biomedical Engineering, Nonlinear dynamics, Fractals, Signal Analysis, and 11 moreStochastic processes, Humans, Computer Simulation, Empirical mode decomposition, Lung Diseases, Artifacts, Reproducibility of Results, Sensitivity and Specificity, Electrical And Electronic Engineering, Respiratory Sounds, and auscultation
The behavior of temporal and spectral parameters of the heart rate variability was determined during 5 different maneuvers in order to characterize the level of sympathetic-vagal activity. The discriminating capacity of two spectral... more
The behavior of temporal and spectral parameters of the heart rate variability was determined during 5 different maneuvers in order to characterize the level of sympathetic-vagal activity. The discriminating capacity of two spectral parameter estimation schemes were compared, and the respiratory influence was evaluated. One hundred and ten records of instantaneous heart rate and respiratory amplitude were analyzed, both in temporal and spectral perspectives. The records were obtained from 22 healthy subjects, under a five-stage protocol: supine, controlled breathing, standing, exercise, and recovery. A discriminating and characteristic behavior was found among the maneuvers, specifically for the dispersion parameters, low and intermediate partial components. The two integration-normalization procedures used in the estimation of the spectral components showed similarities, producing a functional interpretation independent of the selected procedure. The division of the low frequency c...
Research Interests: Algorithms, Humans, Female, Male, Heart rate, and 5 moreExercise, Respiration, Posture, Adult, and Reference Values
Body density by hydrostatic method and anthropometric variables were measured in 29 young males, natives of Mexico City, in order to test the validity of nine currently used equations for predicting body composition. Tested equations were... more
Body density by hydrostatic method and anthropometric variables were measured in 29 young males, natives of Mexico City, in order to test the validity of nine currently used equations for predicting body composition. Tested equations were those reported for body density by Sloan, Wilmore, Jackson and Pollock, Durnin and Womersley, Lohman, and Pollock et al.; for lean body weight by Wilmore, and Hume-Rathbun; and for fat percentage by Yuhasz. Mean values for body density, fat percentage and lean body weight obtained by hydrostatic weighing were 1.0560 +/- 0.0149 kg/l, 18.9 +/- 6.7%, and 52.6 +/- 5.3 kg, respectively, while the means for predicted body density using the six regression equations varied from 1.0538 to 1.0654 kg/l, with a range of correlation from 0.846 to 0.900, and total errors from 0.0077 to 0.0124 kg/l. Mean lean body weight predicted by Wilmore was 55.7 +/- 5.9 kg, with an R of 0.902 and a total error of 4.0 kg, while values given in the same order by Hume-Rathbun w...
Research Interests: Physiology, Mathematics, Anthropometry, Adolescent, Immersion, and 15 moreAdipose tissue, Humans, Body Composition, Male, Regression Analysis, Exploration, Relative Density, Adult, Body Weight, Densitometry, Plethysmography, Lung Volume Measurements, Predictive value of tests, Skinfold Thickness, and Medical and Health Sciences
Crackles sounds have been associated with several pulmonary pathologies and diverse algorithms have been proposed for extracting and counting them from the acquired lung sound. These tasks depend among other factors, of the relation... more
Crackles sounds have been associated with several pulmonary pathologies and diverse algorithms have been proposed for extracting and counting them from the acquired lung sound. These tasks depend among other factors, of the relation between the magnitude of the crackle and the background lung sound. In this work, we explore multivariate signal processing to deal with the tasks and propose a new concept, the discontinuous adventitious sounds imaging. The image formation is founded on the results of two proposed methodologies that use an autoregressive (AR) model. In the first case, the AR coefficients feed an artificial neural network (ANN) to classify temporal acoustic information as healthy or sick and; in the second case, a time-variant AR (TVAR) model, obtained by the RLS algorithm, permits to detect changes in the TVAR coefficients to be associated with the number of crackles. For AR-ANN, the ratio of the temporal windows classified as sick to the classified as healthy is used as an index to form the adventitious image, while for TVAR-RLS, an estimation of the number of crackles is obtained to form the corresponding image. The results indicated that fine and coarse crackles could be detected and counted even with very low crackle magnitude so that the formation of a crackle distribution image was consistent.
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The mechanisms involved in the generation of heart sounds have always been of interest, mainly for diagnosis purposes. As a result, mathematical models have been proposed for first (S1) and second (S2) heart sounds and different efforts... more
The mechanisms involved in the generation of heart sounds have always been of interest, mainly for diagnosis purposes. As a result, mathematical models have been proposed for first (S1) and second (S2) heart sounds and different efforts have been made to select the best signal processing tool to analyze them. Different frequency analysis techniques have been used to relate cardiac structure to the vibration they emit. In this work, we applied the empirical mode decomposition (EMD), a recently developed technique, for time-frequency (TF) analysis of heart sounds. EMD has shown interesting properties for biomedical signals related to nonlinear and non-stationary analysis. EMD is an adaptive decomposition since the extracted information is obtained directly from the signal without the use of kernels or mother waveforms. In this paper, EMD is first investigated in simulated scenarios through mathematical models for SI and S2 to validate its performance. Later, a real heart sound acquired over the thoracic surface of a healthy subject is analyzed. The work points out the advantage of EMD for this task.
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Several attempts have been made to achieve a quantitative analysis of lung sounds mainly for two purposes: a) an understanding of their genesis, and b) an insight of their changes with pathologies for medical diagnosis. Early studies... more
Several attempts have been made to achieve a quantitative analysis of lung sounds mainly for two purposes: a) an understanding of their genesis, and b) an insight of their changes with pathologies for medical diagnosis. Early studies involved the collection of acoustic information at several positions on the thoracic surface or at the extra-thoracic trachea with one up to four microphones, but with a non-simultaneous acquisition. However, an increment for simultaneous acquisition points has been suggested; for example, as a consequence of multichannel acquisition acoustic visualization through computerized interpolation has emerged being helpful to analyze lung sounds (LS) origin, distribution, and relation to ventilation. Nevertheless, quantitative analysis of lung sounds requires eliminating interference signals prior to the extraction of relevant features. The acquired signals not only contain LS but also heart sounds (HS) among other interferences. HS are unavoidable and sometimes represent severe disturbing interference. This paper proposes a HS cancellation scheme as an extension of a previous effort using the Empirical Mode Decomposition (EMD) and a combination of time warping with linear adaptive FIR filtering. Simulated signals are used to evaluate the performance of the proposed scheme under known and controlled scenarios.
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Abnormal lung sounds in diffuse interstitial pneumonia have been characterized by the presence of crackles. However, few attempts have tried to analyze the sound where crackles are immersed. In this work base lung sounds (BLS) were... more
Abnormal lung sounds in diffuse interstitial pneumonia have been characterized by the presence of crackles. However, few attempts have tried to analyze the sound where crackles are immersed. In this work base lung sounds (BLS) were analyzed by linear and nonlinear techniques to find possible differences between normal subjects and patients with diffuse interstitial pneumonia. In both groups, segments of lung sounds (crackles absent) and segments of BLS (lung sound in between crackles) were analyzed from acquired lung sounds from four points at the posterior chest, two apical and two basal. In this study, 8 healthy subjects and 8 patients participated and BLS were analyzed by spectral percentiles and sample entropy. Although spectral percentiles and sample entropy (SampEn) tended to be lower in the group of patients, statistical differences (p0.05) between normal subjects and patients were found in BLS at the left hemithorax at basal and apical regions, while at the right hemithorax significant differences were found only at the basal region using the nonlinear technique. We conclude that in respect to normal subjects, BLS of patients with diffuse interstitial pneumonia present differences as assessed by SampEn, so that BLS by itself provides useful information. Moreover, it seems that nonlinear technique did a better discrimination of abnormal BLS than spectral percentile parameters.
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This work proposes multichannel acquisition of lung sounds by a microphone array, feature extraction by a multivariate AR (MAR) model, dimensionality reduction of the feature vectors (FV) by SVD and PCA and, their classification by a... more
This work proposes multichannel acquisition of lung sounds by a microphone array, feature extraction by a multivariate AR (MAR) model, dimensionality reduction of the feature vectors (FV) by SVD and PCA and, their classification by a supervised neural network. A microphone array of 25 sensors was attached on the thoracic surface of the subjects, who were breathing at 1.5 L/sec. The supervised neural network used the backpropagation learning algorithm based on the Levenberg-Marquardt rule. Figures of merit for the classification task by the neural net include the percentage of correct classification during training, testing and validation phases as well as sensitivity, specificity and performance. MAR in combination with PCA provided the best average percentage of correct classification with acoustic information not seen by the neural network during the training phase (87.68%). The results state the advantages of a microphone array for the classification of normal and abnormal acoustic pulmonary information in diffuse interstitial pneumonia and for this goal, the authors assume that not only the crackles and their number indicates the severity of the disease, but the basal respiratory signal could be also affected.
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Adventitious lung sounds (ALS) as crackles and wheezes are present in different lung alterations and their automated characterization and recognition have become relevant. In fact, recently their 2D spatial distribution (SD) imaging has... more
Adventitious lung sounds (ALS) as crackles and wheezes are present in different lung alterations and their automated characterization and recognition have become relevant. In fact, recently their 2D spatial distribution (SD) imaging has been proposed to help diagnose of pulmonary diseases. In this work, independent component analysis (ICA) by infomax was used to find crackles sources and from them to apply a time variant autoregressive model (TVAR) to count and imaging the ALS. The proposed methodology was assessed on multichannel LS recordings by embedding simulated fine crackles with known SD in recorded normal breathing sounds. Afterwards, the adventitious image of two patients with fibrosis and emphysema were obtained and contrasted with the classical pulmonary auscultation provided by a pneumologist. The results showed that combining ICA and TVAR leads to a robust methodology to imaging ALS.
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The interpretation of heart rate patterns obtained by fetal monitoring relies on the definition of a baseline, which is considered as the running average heart rate in the absence of external stimuli during periods of fetal rest. We... more
The interpretation of heart rate patterns obtained by fetal monitoring relies on the definition of a baseline, which is considered as the running average heart rate in the absence of external stimuli during periods of fetal rest. We present a study along gestation of the baseline's fluctuations, in relation to fractal and nonlinear properties, to assess these fluctuations according with time-varying attracting levels introduced by maturing regulatory mechanisms. A low-risk pregnancy was studied weekly from the 17th to 38th week of gestation during long-term recording sessions at night (>6 h). Fetal averaged pulse rate samples and corresponding baseline series were obtained from raw abdominal ECG ambulatory data. The fractal properties of these series were evaluated by applying detrended fluctuation analysis. The baseline series were also explored to evaluate nonlinear properties and time ordering by applying the scaling magnitude and sign analyses. Our main findings are that the baseline shows fractal and even nonlinear anticorrelated fluctuations. This condition was specially the case before mid-gestation, as revealed by α values near to unit, yet becoming significantly more complex after 30 weeks of gestation as indicated by α(mag) values >0.5. The structured (i.e. not random) fluctuations and particular nonlinear changes that we found thus suggest that the baseline provides on itself information concerning the functional integration of cardiac regulatory mechanisms.
Research Interests: Engineering, Nonlinear dynamics, Fractals, Pregnancy, Humans, and 13 moreFemale, Physical sciences, Heart rate, Newborn Infant, Functional integration, Time Factors, Pulse Rate, Low Risk, Detrended Fluctuation Analysis, Time varying, Fetal Heart Rate, Scaling Exponent, and Medical and Health Sciences
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Indices obtained from the second derivative of the digital volume pulse waveform have been proposed to characterize vascular aging, arterial rigidity, and the effects of vasoactive drugs. The purpose of this study was to assess the... more
Indices obtained from the second derivative of the digital volume pulse waveform have been proposed to characterize vascular aging, arterial rigidity, and the effects of vasoactive drugs. The purpose of this study was to assess the effects of manual needling of PC6 on SDDVP indices in healthy and untreated hypertensive subjects. AI, B:A, and D:A indices, based on the height of the wave components of SDDVP, in 40 healthy subjects and 25 untreated hypertensive subjects were compared. DVP was obtained by measuring infrared light transmission through the finger. For each subject, 20-min-long DVP registration was obtained. PC6 was stimulated unilaterally by manual needling for 5 min (1–6 min). In each subject, pre-acupuncture DVP indices were compared to those of during acupuncture (1 vs. 4 min) and post-acupuncture (1 vs. 18 min). In healthy subjects, AI was significantly improved when comparing the pre- to the post-acupuncture values. In hypertensive subjects, the SDDVP indices improved significantly as follows: the AI index when the value of pre-acupuncture comparing to that of during acupuncture and post-acupuncture values; B:A and D:A indices when the pre-comparing to post-acupuncture values. There were significant differences between healthy and hypertensive subjects in AI, B:A, and D:A at baseline and in B:A in the during acupuncture period; there were no significant differences at post-acupuncture. These results indicate that manual needling of PC6 produced acute effects on vascular pathophysiology. Moreover, PC6 needling produced changes in SDDVP indices related to both large artery stiffness and the reflected wave originating in small arteries.
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Time-varying autoregressive modeling may consider the driving noise variance as a constant. In this work, the properties of the autoregressive driving noise variance of heart rate variability, with different stationary physiological... more
Time-varying autoregressive modeling may consider the driving noise variance as a constant. In this work, the properties of the autoregressive driving noise variance of heart rate variability, with different stationary physiological conditions (resting in supine and sitting; exercise) are obtained. The effect of constant variance consideration for ramp exercise and recovery (a nonstationary condition) is also evaluated by the comparison of the time-varying absolute spectral parameters obtained by parametric estimation, allowing or not the modeling of time-varying noise variance, and a non-parametric time-frequency analysis. The driving noise variance presented a direct non-linear relationship with the heart period for the stationary maneuvers (r=0.91), while for the nonstationary condition, the use of a constant driving noise resulted in bias for the estimation of heart rate variability spectral parameters. A time-varying driving noise variance should be considered.
Research Interests: Algorithms, Medicine, Electrocardiography, Time-Frequency Analysis, Heart rate variability, and 13 moreHumans, Computer Simulation, Female, Male, Regression Analysis, Heart rate, Time Frequency Analysis, Adult, Reproducibility of Results, Parametric Estimation, Sensitivity and Specificity, Time varying, and Autoregressive model
An exercise program based on growing intensity loads (50 watts) was applied to 21 healthy, middle-aged subjects, who were divided into two groups: the physically actives and the sedentaries, according to their physical activity habits.... more
An exercise program based on growing intensity loads (50 watts) was applied to 21 healthy, middle-aged subjects, who were divided into two groups: the physically actives and the sedentaries, according to their physical activity habits. During exercise, which was made on a treadmill, the following variables were measured: oxygen intake (VO2), cardiac frequency (FC), left ventricule ejection time (TEVI), maximal value of the first derivative of ear ensitogram (VMPDDO) and indirect arterial pressure. The active group reached higher values of power and VO2 (absolute and by pulse) and lower values of FC at under maximal works; these data therefore show their best cardiopulmonary capacity. The TEVI in the active group was higher at 150 watts because of the lower FC presented by its assigned subjects. For a maximal exercise condition, both groups had similar ejection times, but the reduction rate of actives' TEVI decreased, which in turn indicates the handling of higher stroke volumes....
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In order to compare 1) predicted values of aerobic capacity (VO2Max) and, 2) direct VO2Max reported in the literature for sedentary subjects, direct VO2Max was measured in 27 sedentary males (18-25 years old), residents at 2240 meters... more
In order to compare 1) predicted values of aerobic capacity (VO2Max) and, 2) direct VO2Max reported in the literature for sedentary subjects, direct VO2Max was measured in 27 sedentary males (18-25 years old), residents at 2240 meters (588.5 +/- 1.0 mmHg). To get direct VO2Max, ventilation and expired gases were measured while the subjects performed maximal exercise on a motor treadmill. Predicted VO2Max was estimated from the Astrand and Ryhming nomogram by measuring submaximal heart rate (HR) during a step test protocol. The mean results from the maximal protocol were: HR 194.9 +/- 5.4 beats/min, direct VO2Max 3.15 +/- 0.46 L/min and 47.67 +/- 5.07 ml/min/Kg, absolute and relative to body weight, respectively. From the submaximal protocol, mean HR was 171 +/- 8.3 beats/min and predicted VO2Max 2.50 +/- 0.39 L/min. In spite of a good correlation (r = 0.79) between predicted and direct VO2Max, the predicted values underestimated 20.3 +/- 7.2% direct measurements. Our data point out ...
Research Interests: Adolescent, Humans, Male, Heart rate, Exercise, and 4 moreAdult, Altitude, Exercise Test, and Oxygen Consumption
Uterine electromyogram on the abdomen of pregnant women (electrohysterogram, EHG) plays an interesting role to evaluate possible risks to the binomial mother-fetus. In this sense, the present study explored the characterization of... more
Uterine electromyogram on the abdomen of pregnant women (electrohysterogram, EHG) plays an interesting role to evaluate possible risks to the binomial mother-fetus. In this sense, the present study explored the characterization of contractions by EHG during active phase of labor at term in a population at low risk. The goal was to investigate the differences in the contractions generated by women that evolve labor to a vaginal delivery (group 1) to those associated with caesarean section (group 2). Abdominal signals were acquired using Ag-AgCl electrodes in a bipolar configuration and the EHG was obtained by band-pass filtering in the range of 0.3 to 4 Hz. Sample entropy (SampEn) was used to calculate the irregularity of manually selected contractions of the EHG time series. The results showed that it is plausible to discriminate contractions from both groups as the average SampEn was 2.1359 with a standard deviation of 0.0583 for group 1 (N=8), while for group 2 (N=8) was 2.0352 with standard deviation of 0.0946; it was found significant statistical difference between groups as p was 0.046. Consequently, the nonlinear analysis via SampEn of EHG could provide an index to evaluate the quality of the active phase labor at term.
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Heartbeat fluctuations show fractal-like correlations that are associated with highly adaptive cardiovascular regulatory systems. Moreover, the short-range fractal or scaling exponent alpha(1) extracted from these correlations has been... more
Heartbeat fluctuations show fractal-like correlations that are associated with highly adaptive cardiovascular regulatory systems. Moreover, the short-range fractal or scaling exponent alpha(1) extracted from these correlations has been found to be a predictor of mortality for subjects with an impaired left ventricular function. In general, the RR-interval data required for this analysis are derived from long-term ECG recordings during free-running conditions. Yet short-term recordings are more likely to be obtained in some practical circumstances, so becoming relevant to assess the possibility of obtaining representative alpha(1) exponents from these recordings. Here, we compare the alpha(1) exponents extracted from the RR-interval series (9:00 AM-6:00 PM) of 51 healthy adults in normal sinus rhythm and the alpha(1) calculated from three shorted segments of only 700 beats obtained from the same series at 9:00 AM, 1:30 PM and 5:00 PM. We found no significant differences between the scaling exponents derived from the whole 9 h series and the short segments at 9:00 AM and 5:00 PM, but did find significant differences when comparing the whole series with the short segment at 1:30 PM. Thus, only if the time of day is taken into consideration can short segments of heartbeat fluctuation data be used to obtain representative alpha(1) exponents.
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Summary Objective: To assess the feasibility to generate a confident image of normal breath sounds (BS) based on the quantitative analysis of multichannel sensors and imaging them in three known clinical classes, i.e., tracheal, bronchial... more
Summary Objective: To assess the feasibility to generate a confident image of normal breath sounds (BS) based on the quantitative analysis of multichannel sensors and imaging them in three known clinical classes, i.e., tracheal, bronchial and vesicular, identifying their spatial distribution with high resolution on the posterior thoracic surface. Methods: Three parametrization techniques, the percentile frequencies, the univariate AR modeling, and the eigenvalues of the covariance matrix were evaluated when applied to BS. These sounds were acquired in twelve healthy subjects by a 5 × 5 sensor array on the posterior thoracic surface plus the sound at the tracheal position, to obtain feature vectors that fed a supervised multilayer neural network. Based on BS classification rate, the spatial distribution of each BS class was obtained by constructing an image using deterministic interpolation. Results: The univariate AR modeling was the best parametrization technique producing a classi...
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The effect of an orthostatic stress on cardiovascular and respiratory complexity was investigated to detect impaired autonomic regulation in patients with vasovagal syncope (VVS). Sixteen female patients and 12 age-matched healthy female... more
The effect of an orthostatic stress on cardiovascular and respiratory complexity was investigated to detect impaired autonomic regulation in patients with vasovagal syncope (VVS). Sixteen female patients and 12 age-matched healthy female subjects were enrolled in a passive 70° head-up tilt test. Also, 12 age-matched healthy male subjects were enrolled to study gender differences. Analysis was performed dynamically using various short-term (5 min) windows shifted by 1 min as well as by 20 min of orthostatic phase (OP) to evaluate local and global complexity. Complexity was determined over multiple time scales by the established method of refined composite multiscale entropy (RCMSE) and by a new proposed method of multiscale entropy based on symbolic dynamics (MSE-SD). Concerning heart rate variability (HRV) during OP, both methods revealed the highest complexity for female controls followed by lower complexity in male controls (p<0.01) and by the lowest complexity in female patien...
Interstitial lung diseases (ILDs) have been increasing their relevance in loss of lives according to a recent world wide medical information. Idiopathic pulmonary fibrosis (IPF) and combined pulmonary fibrosis and emphysema syndrome... more
Interstitial lung diseases (ILDs) have been increasing their relevance in loss of lives according to a recent world wide medical information. Idiopathic pulmonary fibrosis (IPF) and combined pulmonary fibrosis and emphysema syndrome (CPFES) belong to ILD class with the latter having a limited survival prognosis. In clinical environment high resolution computed tomography (HRCT) is used to detect CPFE; however, there is still controversy about the amount of emphysema observed in HRCT to declare CPFES. Consequently, to help in the diagnosis of CPFES to develop an alternative technique seems to be attractive. In this study, we propose a multichannel acoustic approach to discriminate between IPF and CPFES parameterizing the multichannel lung sounds information linearly and classifying it by neural networks (NN). The NN performance using different features provided values above 90% in the validation phase. Furthermore, to test the trained NN, the proposed approach was applied on new data...
The combined pulmonary fibrosis emphysema syndrome (CPFES) overall has a poor prognosis with a 5-year survival of 35-80%. Consequently, to evaluate possible positive effects on patients of novel agents as pirfenidone is relevant. However,... more
The combined pulmonary fibrosis emphysema syndrome (CPFES) overall has a poor prognosis with a 5-year survival of 35-80%. Consequently, to evaluate possible positive effects on patients of novel agents as pirfenidone is relevant. However, the efficacy of pirfenidone in CPFES patients is still not well-known. In this study we propose an alternative to evaluate the effects of pirfenidone treatment on CPFES patients via acoustic information. Quantitative analysis of discontinuous adventitious lung sounds (DLS), known as crackles, has been promising to detect and characterize diverse pulmonary pathologies. The present study combines independent components (ICs) analysis of LS and the automated selection of ICs associated with DLS. ICs&#39;s features as fractal dimension, entropy and sparsity produce several clusters by kmeans. Those clusters containing ICs of DLS are exclusively considered to finally estimate the number of DLS per ICs by a time-variant AR modeling. For the evaluation of the effects of pirfenidone, the 2D DLS-ICs spatial distribution in conjunction with the estimated number of DLS events are shown. The methodology is applied to two real cases of CPFES with 6 and 12 months of treatment. The acoustical evaluation indicates that pirfenidone treatment may not be satisfactory for CPFES patients but further evaluation has to be performed.
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Discontinuous lung sounds (DLS), also known as crackles, are abnormal sounds produced by different pulmonary pathologies (PP) whose thoracic spatial distribution and prevalence are relevant for diagnosis purpose. Recently, DLS imaging has... more
Discontinuous lung sounds (DLS), also known as crackles, are abnormal sounds produced by different pulmonary pathologies (PP) whose thoracic spatial distribution and prevalence are relevant for diagnosis purpose. Recently, DLS imaging has been proposed to help diagnose and follow-up PP where automated recognition of DLS is meaningful. The present study focuses on the automated selection of independent components (ICs) associated with DLS. Extraction of ICs information for clustering by k-means is achieved in two ways: (1) forming features vectors (FVs) containing the kurtosis, entropy and sparsity of each IC or (2) by applying mutual information (MI) or Euclidean distance (ED) to all ICs. Next, silhouette index is computed to estimate the number of necessary clusters (C). Afterward, to detect just the clusters containing ICs of DLS a selection index is proposed. Finally, to estimate the number of DLS per ICs in each selected cluster a time-variant AR modeling is applied; the estimated number is shown in conjunction with the 2D-ICs spatial distribution. The methodology is applied to simulated and real cases; DLS imaging results are also compared against clinical auscultation. The results showed that the automated selection via FVs is promising to imaging DLS.
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To determine maternal hemoglobin behavior during pregnancy for middle altitude residents and to compare it with that reported in other populations with or without iron supplementation. Hematological values from 227 pregnant women residing... more
To determine maternal hemoglobin behavior during pregnancy for middle altitude residents and to compare it with that reported in other populations with or without iron supplementation. Hematological values from 227 pregnant women residing at 2 240 m altitude (Mexico City), with low obstetric and perinatal risk, and receiving supplementary iron, were compared with reference values obtained from other populations of pregnant women residing at different altitudes, after correcting for altitude. While the hemoglobin values for the first and second trimester of pregnancy in our studied population were similar to those reported for iron-supplemented populations (p>0.05), the third trimester values were similar to those reported for a population without this supplement (p>0.05). Despite receiving supplementary iron, hemoglobin values during pregnancy from women residing at middle altitude show similar behavior to that reported for pregnant women without iron supplementation.
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Several techniques have been explored to detect automatically fine and coarse crackles; however, the solution for automatic detection of crackles remains insufficient. The purpose of this work was to explore the capacity of the... more
Several techniques have been explored to detect automatically fine and coarse crackles; however, the solution for automatic detection of crackles remains insufficient. The purpose of this work was to explore the capacity of the time-variant autoregressive (TVAR) model to detect and to provide an estimate number of fine and coarse crackles in lung sounds. Thus, simulated crackles inserted in normal lung sounds and real lung sounds containing adventitious sounds were processed with TVAR and by an expert that based crackle detection on time-expanded waveform-analysis. The coefficients of the TVAR were obtained by an adaptive filtering prediction scheme. The adaptive filter used the recursive least squares algorithm with a forgetting factor of 0.97 and the model order was four. TVAR model showed an efficiency to detect crackles over 90% even with crackles overlapping and amplitudes as low as 1.5 of the standard deviation of background lung sounds, where expert presented an efficiency ar...
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The reliability of 33 prediction models for vital capacity was assessed in university students living in Mexico City (altitude = 2,240 m). Forced vital capacity (FVC) was predicted and measured in 83 healthy male students, 18 to 30 years... more
The reliability of 33 prediction models for vital capacity was assessed in university students living in Mexico City (altitude = 2,240 m). Forced vital capacity (FVC) was predicted and measured in 83 healthy male students, 18 to 30 years old and non-smokers. Spirometric tests were performed with a 9 liter bell spirometer, according to ATS guidelines. Mean measured FVC was 5,094 +/- 555 mL (BTPS) while mean predicted FVC by the models ranged from 3,700 mL to 5,350 mL (BTPS) with a small but significative correlation between actual and reference values (r = 0.398 to 0.474, p < 0.05). The residual standard deviation showed values from 503 to 577 mL which were similar to those seen in the original population. Although 11 of the 33 models were able to predict mean observed FVC by Dunnett's test (p < 0.05), all of them showed significant bias on the regression between measured values and residuals of predicted values, i.e. intercepts (2,435 to 4,127 mL), slopes (-0.61 to -0.87) ...
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ABSTRACT
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Pulmonary gas exchange was studied in eight normal subjects both before and after 2 wk of altitude acclimatization at 3,800 m (12,470 ft, barometric pressure = 484 Torr). Respiratory and multiple inert gas tensions, ventilation, cardiac... more
Pulmonary gas exchange was studied in eight normal subjects both before and after 2 wk of altitude acclimatization at 3,800 m (12,470 ft, barometric pressure = 484 Torr). Respiratory and multiple inert gas tensions, ventilation, cardiac output (Q), and hemoglobin concentration were measured at rest and during three levels of constant-load cycle exercise during both normoxia [inspired PO2 (PIO2) = 148 Torr] and normobaric hypoxia (PIO2 = 91 Torr). After acclimatization, the measured alveolar-arterial PO2 difference (A-aPO2) for any given work rate decreased (P less than 0.02). The largest reductions were observed during the highest work rates and were 24.8 +/- 1.4 to 19.7 +/- 0.8 Torr (normoxia) and 22.0 +/- 1.1 to 19.4 +/- 0.7 Torr (hypoxia). This could not be explained by changes in ventilation-perfusion inequality or estimated O2 diffusing capacity, which were unaffected by acclimatization. However, Q for any given work rate was significantly decreased (P less than 0.001) after ac...
Research Interests: Biological Sciences, Methods, Humans, Applied, Female, and 15 moreMale, Exercise, Atmospheric Pressure, Applied Physiology, Lung, Respiration, Middle Aged, Adult, Sex Factors, Acclimatization, Altitude, Lung Volume Measurements, Pulmonary ventilation, Pulmonary Gas Exchange, and Medical and Health Sciences
ABSTRACT Several indexes at time and spectral domains for assessment of the respiratory sinus arrhythmia have been proposed but none of them is yet considered as the reference. The goal of the present work was to describe how those... more
ABSTRACT Several indexes at time and spectral domains for assessment of the respiratory sinus arrhythmia have been proposed but none of them is yet considered as the reference. The goal of the present work was to describe how those indexes represent the low-pass characteristic of the sinus node in a broad range of breathing frequencies, and to evaluate the discriminative capacity of them over heart rate. Time and frequency domain parameters were calculated from the RR intervals and breathing series obtained at eight frequency rates of controlled breathing. We assumed an autoregressive with exogenous input variable model that related the changes in heart rate (output) to changes in respiration (input or exogenous variable). Spectral parameters were computed using this model. The statistical discrimination capacity of pairs of means at those frequencies was evaluated. For those indexes with higher capacity, the cut off frequency was computed. The results proved that the temporal index gain had the best discriminative capacity because it is less sensitive to the inter-individual variability. However, the indexes with higher capacity reflected appropriately the low-pass behavior of the sinus node.
ABSTRACT
Blind source separation by independent component analysis has been applied extensively in the biomedical field for extracting different contributing sources in a signal. Regarding lung sounds analysis to isolate the adventitious sounds... more
Blind source separation by independent component analysis has been applied extensively in the biomedical field for extracting different contributing sources in a signal. Regarding lung sounds analysis to isolate the adventitious sounds from normal breathing sound is relevant. In this work the performance of FastICA, Infomax, JADE and TDSEP algorithms was assessed using different scenarios including simulated fine and coarse crackles embedded in recorded normal breathing sounds. Our results pointed out that Infomax obtained the minimum Amari index (0.10037) and the maximum signal to interference ratio (1.4578e+009). Afterwards, Infomax was applied to 25 channels of recorded normal breathing sound where simulated fine and coarse crackles were added including acoustic propagation effects. A robust blind crackle separation could improve previous results in generating an adventitious acoustic thoracic imaging.
Research Interests:
Research Interests:
It is now widely accepted that crackles are associated with different pulmonary pathologies and different efforts have been done to detect and to extract them. Consequently, due to the difficulty for their characterization, the selection... more
It is now widely accepted that crackles are associated with different pulmonary pathologies and different efforts have been done to detect and to extract them. Consequently, due to the difficulty for their characterization, the selection of an adequate time-frequency representation (TFR) for the analysis of their time-frequency dynamics is important. Traditionally, normal and abnormal lung sounds have been analyzed by the Spectrogram (SP). However, this analysis tool has certain disadvantages when one deals with nonstationary signals. As an effort to point out the appropriate analysis tool for crackles, this paper shows the performance of the Hilbert-Huang spectrum (HHS) for the analysis of fine and coarse crackles, simulated and real ones. The HHS allowed to analyze the evolving time-frequency of crackle sounds straightforward with good resolution compared with SP. Beside this enhanced time-frequency course, HHS could be useful to establish a signature to detect and separate fine from coarse crackles in order to screen pathologies and their progress during medication.
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Several researches have tried to provide a means to analyze the second heart sound (S2) in an attempt to understand the functional mechanisms in its genesis and for diagnosis purposes. In this work we tested Time-Frequency Representation... more
Several researches have tried to provide a means to analyze the second heart sound (S2) in an attempt to understand the functional mechanisms in its genesis and for diagnosis purposes. In this work we tested Time-Frequency Representation (TFR) for simulated S2 selecting and applying classical and modern TFRs such as the Spectrogram, the Wigner-Ville Distribution, the Time Varying Autoregressive (TVAR) model, the Scalogram, and the Hilbert-Huang Spectrum (HHS) by Empirical Mode Decomposition. Two performance measures are proposed, the first one based on local 2D correlations (rho) between the ideal and the estimated TFRs images, while the second one based on time moments of the TFR images to provide the normalized root-mean-square error (NRMSE). Under no noise conditions, the TFRs by HHS and the TVAR modeling, by the Burg algorithm, resulted in a rho(average) of 0.788 and 0.812, and NRMSE of 0.172 and 0.195, respectively. Therefore, based on the lowest NRMSE, HHS was considered the TFR with the best performance. Afterward, HHS was applied to real S2 acquired at the aortic and pulmonary focal points.
Research Interests: Algorithms, Software, Humans, Computer Simulation, Empirical mode decomposition, and 14 moreHeart, Root-Mean Square Error, Spectrum, Heart valves, Theoretical Models, Time Factors, Time Frequency Representation, Wigner Ville Distribution, Aorta, Focal Point, Performance Measure, Time varying, heart sounds, and phonocardiography
Research Interests:
Research Interests:
RATHI was introduced as an attempt to further improve the association between anatomical zones and specific breathing activity, both spatially and temporally. This work compares RATHI with clinical pulmonary auscultation (PA) to assess... more
RATHI was introduced as an attempt to further improve the association between anatomical zones and specific breathing activity, both spatially and temporally. This work compares RATHI with clinical pulmonary auscultation (PA) to assess the concordance between both procedures to detect asymmetries in lung sound (LS) intensities. Twelve healthy young males participated in the study and were auscultated by two experts. RATHI consisted in the acquisition of acoustical signals with an array of 5x5 sensors, while experts auscultated and described the intensity of LS heard using the same stethoscope on each sensor&#39;s position within the array. Comparisons were established looking for intensity asymmetries between apical vs. basal pulmonary regions and right vs. left hemithorax. By RATHI, most of the subjects showed asymmetries between apical and basal regions higher than 20%, whereas between left and right hemithorax asymmetries higher than 20% occurred only half of the time. RATHI and PA agreed 83 to 100% when apical to base acoustical information was compared, but when left to right asymmetries were considered these figures were about 40 to 50%. We concluded that RATHI has advantages as it gave more detailed and measurable information on LS than clinicians, who could not detect intensity asymmetries mainly below 20%.
Research Interests:
Time-varying autoregressive modeling may consider the driving noise variance as a constant. In this work, the properties of the autoregressive driving noise variance of heart rate variability, with different stationary physiological... more
Time-varying autoregressive modeling may consider the driving noise variance as a constant. In this work, the properties of the autoregressive driving noise variance of heart rate variability, with different stationary physiological conditions (resting in supine and sitting; exercise) are obtained. The effect of constant variance consideration for ramp exercise and recovery (a nonstationary condition) is also evaluated by the comparison of the time-varying absolute spectral parameters obtained by parametric estimation, allowing or not the modeling of time-varying noise variance, and a non-parametric time-frequency analysis. The driving noise variance presented a direct non-linear relationship with the heart period for the stationary maneuvers (r=0.91), while for the nonstationary condition, the use of a constant driving noise resulted in bias for the estimation of heart rate variability spectral parameters. A time-varying driving noise variance should be considered.
Research Interests: Algorithms, Medicine, Electrocardiography, Time-Frequency Analysis, Heart rate variability, and 13 moreHumans, Computer Simulation, Female, Male, Regression Analysis, Heart rate, Time Frequency Analysis, Adult, Reproducibility of Results, Parametric Estimation, Sensitivity and Specificity, Time varying, and Autoregressive model
Gender related-differences in the autonomic regulation of the cardiovascular and cardiorespiratory systems have been studied mainly by hemodynamic responses during different physical stressors. In this study, the influence of gender on... more
Gender related-differences in the autonomic regulation of the cardiovascular and cardiorespiratory systems have been studied mainly by hemodynamic responses during different physical stressors. In this study, the influence of gender on the autonomic response to an orthostatic challenge was investigated by obtaining the cardiovascular and cardiorespiratory coupling using the nonlinear technique known as joint symbolic dynamics (JSD) representation. This study includes 24 healthy young subjects. Males (N=12) and age-matched females (N=12) were enrolled in a head-up tilt (HUT) test, breathing normally, including 5 minutes of supine position (baseline) and 25-40 minutes of 70° orthostatic phase. The cardiovascular and cardiorespiratory couplings were obtained at baseline, early and middle orthostatic phases. Although in baseline there were some gender differences, parameters from JSD showed highly significant (p=0.0004) differences in specific cardiovascular coupling patterns in the ear...
Indices obtained from the second derivative of the digital volume pulse waveform have been proposed to characterize vascular aging, arterial rigidity, and the effects of vasoactive drugs. The purpose of this study was to assess the... more
Indices obtained from the second derivative of the digital volume pulse waveform have been proposed to characterize vascular aging, arterial rigidity, and the effects of vasoactive drugs. The purpose of this study was to assess the effects of manual needling of PC6 on SDDVP indices in healthy and untreated hypertensive subjects. AI, B:A, and D:A indices, based on the height of the wave components of SDDVP, in 40 healthy subjects and 25 untreated hypertensive subjects were compared. DVP was obtained by measuring infrared light transmission through the finger. For each subject, 20-min-long DVP registration was obtained. PC6 was stimulated unilaterally by manual needling for 5 min (1–6 min). In each subject, pre-acupuncture DVP indices were compared to those of during acupuncture (1 vs. 4 min) and post-acupuncture (1 vs. 18 min). In healthy subjects, AI was significantly improved when comparing the pre- to the post-acupuncture values. In hypertensive subjects, the SDDVP indices improve...
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Summary Objective: Pulmonary disorders are frequently characterized by the presence of adventitious sounds added to the breathing or base lung sound (BLS). The aim of this work was to assess the features of BLS in extrinsic allergic... more
Summary Objective: Pulmonary disorders are frequently characterized by the presence of adventitious sounds added to the breathing or base lung sound (BLS). The aim of this work was to assess the features of BLS in extrinsic allergic alveolitis (EAA) patients in comparison to healthy subjects, applying linear and nonlinear analysis techniques. Methods: We investigated the multichannel lung sounds on the posterior chest of 16 females, 8 healthy and 8 EAA patients, when breathing at 1.5 L/s. BLS linear features were obtained from the power spectral density (PSD) while nonlinear features were extracted by the concepts of irregularity and complexity, i.e., spectral, sample and multi-scale entropy. Results: The results demonstrated that spectral percentiles of BLS were lower in EAA patients than in healthy subjects but statistical significance (p<0.05) was obtained only for expiration at the left apical and both basal regions. Also, the maximum amplitude of the PSD in patients reached ...