Characterization of systolic and diastolic pressure time series in pregnant women with preeclampsia through symbolic dynamics.

Preeclampsia (PE) is one of the leading causes of maternal mortality worldwide. Although clinical strategies to prevent the early onset of PE have been proposed, the ultimate solution is to end the pregnancy. Therefore, patients' identification with major PE risk is important towards the prevention and better management of a severe manifestation of the illness.

Hemodynamic response to low-flow acute supplemental oxygen in idiopathic pulmonary fibrosis and elderly healthy subjects.

Background: Hemodynamic response to supplemental oxygen in idiopathic pulmonary fibrosis (IPF) is still not well known.

Objective: To determine and compare the effect of low-flow acute supplemental oxygen on the hemodynamics of IPF patients and matched healthy subjects.

Methods: Descriptive and comparative study in 20 IPF-patients and 19 Control-subjects, (60-80 years old) breathing ambient air followed by acute nasal low-flow (3 L/min) supplemental oxygen.

Temporal cardiovascular causality during orthostatic stress by extended partial directed coherence.

The aim of this study was to investigate the temporal dynamic behavior of cardiovascular interactions between heart period and systolic blood pressure during a 20-min head-up tilt test at 70° in young women with orthostatic intolerance compared to healthy women. Methods included the lagged and extended partial directed coherence applied to short-term windows shifted by 5 seconds, extracted from a multivariate set of cardiovascular and respiratory time series. Findings revealed significantly increased information flow (p <; 0.

Time-Frequency Analysis of Cardiovascular and Cardiorespiratory Interactions During Orthostatic Stress by Extended Partial Directed Coherence.

In this study, the linear method of extended partial directed coherence (ePDC) was applied to establish the temporal dynamic behavior of cardiovascular and cardiorespiratory interactions during orthostatic stress at a 70° head-up tilt (HUT) test on young age-matched healthy subjects and patients with orthostatic intolerance (OI), both male and female. Twenty 5-min windows were used to analyze the minute-wise progression of interactions from 5 min in a supine position (baseline, BL) until 18 min of the orthostatic phase (OP) without including pre-syncopal phases. Gender differences in controls were present in cardiorespiratory interactions during OP without compromised autonomic regulation.

Cardiovascular variability in young male and female subjects in health and orthostatic intolerance.

The aim of this study was to investigate the effect of head-up tilt (HUT) test on male and female young patients, diagnosed with orthostatic intolerance (OI), in comparison to male and female healthy subjects. Twenty seven OI patients (21 women, 6 men) and 26 age-matched healthy subjects (13 women, 13 men) were enrolled in a 70° HUT test. In addition to hemodynamic variables, cardiovascular and respiratory parameters were determined using linear and nonlinear methods to analyze heart rate (HRV) and blood pressure variability (BPV).

Study of impaired cardiovascular and respiratory coupling during orthostatic stress based on joint symbolic dynamics.

The present study investigates the instantaneous coupling among the cardiac, vascular, and respiratory systems, using the heart rate, respiration, and systolic and diastolic blood pressure variability in 12 healthy and 16 vasovagal syncope female subjects during a head-up tilt (HUT) testing protocol at 70° This study contributes to the coupling analysis by using a nonlinear joint symbolic dynamics (JSD) in a high-temporal resolution scheme, based on 5 min segments of the time series that are shifted every minute. For each segment, a bivariate JSD matrix was constructed to obtain global and local coupling indices in accordance to Shannon's entropy and the probability of occurrence of various bivariate words, respectively. The novel approach revealed important findings in the coupling dynamics of the systems, thus allowing the detection of group differences during the early orthostatic phase, and during the HUT test, before the occurrence of any pre-syncopal symptoms.

Multivariate symbolic dynamics for analysis of respiratory-cardiovascular interactions.

In this work, a nonlinear method to study multivariate interactions, called multivariate symbolic dynamics (MSD), was introduced. The usefulness of this technique was studied on respiratory-cardiovascular data from young women with vasovagal syncope (VVS) and from healthy subjects. The study included 16 female patients diagnosed with VVS and 24 age-matched healthy subjects (12 women).

Temporal Analysis of Cardiovascular and Respiratory Complexity by Multiscale Entropy Based on Symbolic Dynamics.

The effect of an orthostatic stress on cardiovascular and respiratory complexity was investigated to detect impaired autonomic regulation in patients with vasovagal syncope (VVS). A total of 16 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.

Delta space plot analysis of cardiovascular coupling in vasovagal syncope during orthostatic challenge.

In this work, a graphical method to study cardiovascular coupling, called delta space plot analysis (DSPA), was introduced. The graphical representation is susceptible to be parameterized in shape and orientation. The usefulness of this technique was studied on cardiovascular data from patients with vasovagal syncope (VVS) and from controls.

Dynamics of the cardiovascular autonomic regulation during orthostatic challenge is more relaxed in women.

Linear dynamic analysis of cardiovascular and respiratory time series was performed in healthy subjects with respect to gender by shifted short-term segments throughout a head-up tilt (HUT) test. Beat-to-beat intervals (BBI), systolic (SYS) and diastolic (DIA) blood pressure and respiratory interval (RESP) time series were acquired in 14 men and 15 women. In time domain (TD), the descending slope of the auto-correlation function (ACF) (BBI_a31cor) was more pronounced in women than in men (p<0.

Men and women should be separately investigated in studies of orthostatic challenge due to different gender-related dynamics of autonomic response.

In studies of autonomic regulation during orthostatic challenges only a few nonlinear methods have been considered without investigating the effect of gender in young controls. Especially, the temporal development of the autonomic regulation has not yet been explicitly analyzed using short-term segments in supine position, transition and orthostatic phase (OP). In this study, nonlinear analysis of cardiovascular and respiratory time series was performed to investigate how nonlinear indices are dynamically changing with respect to gender during orthostatic challenges.

Orthostatic stress causes immediately increased blood pressure variability in women with vasovagal syncope.

The cardiovascular and respiratory autonomic nervous regulation has been studied mainly by hemodynamic responses during different physical stressors. In this study, dynamics of autonomic response to an orthostatic challenge was investigated by hemodynamic variables and by diverse linear and nonlinear indices calculated from time series of beat-to-beat intervals (BBI), respiratory cycle duration (RESP), systolic (SYS) and diastolic (DIA) blood pressure. This study included 16 young female patients (SYN) with vasovagal syncope and 12 age-matched female controls (CON).

Temporal analysis of cardiac autonomic regulation during orthostatic challenge by short-term symbolic dynamics.

The gradual shift of cardiac autonomic regulation toward sympathetic predominance and vagal withdrawal during graded head-up tilt test in young controls has been demonstrated by parameters from symbolic dynamics obtained from short-term heart rate variability (HRV) analysis. In this study, the influence of gender and vasovagal syncope (VVS) on the autonomic response to an orthostatic challenge was investigated by HRV analysis using short-term symbolic dynamics (STSD). This study included 24 healthy young subjects (12 males; 12 age-matched females) and 16 female patients diagnosed with VVS.

Respiratory sinus arrhythmia in growth restricted fetuses with normal Doppler hemodynamic indices.

Background: The autonomic behavior of growth-restricted fetuses at different evolving hemodynamic stages has not been fully elicited.

Aim: To analyze the respiratory sinus arrhythmia (RSA) of growth-restricted fetuses that despite this severe condition show normal Doppler hemodynamics.

Subjects: 10 growth-restricted fetuses (FGR group) with normal arterial pulsatility indices (umbilical, uterine, middle cerebral, ductus venosus and aortic isthmus), and 10 healthy fetuses (Control group), 32-37weeks of gestation.

Gender differences in cardiovascular and cardiorespiratory coupling in healthy subjects during head-up tilt test by Joint Symbolic Dynamics.

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.

[Hemoglobin values for pregnant women residing at middle altitude].

Objective: 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.

Materials And Methods: 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.

Results: 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.

The autonomic condition of children with congenital hypothyroidism as indicated by the analysis of heart rate variability.

Early treatment by thyroid hormone in congenital hypothyroidism (CH) prevents for mental retardation, but the autonomic condition could well remain impaired. The aim of this study was to get insights about the cardiovascular regulation of CH children by analysing their heart rate variability (HRV) data. RR-interval data of 34 early treated CH children, 24 to 48 months of age, were collected at rest in a clinical environment.

Implementation of a real-time algorithm for maternal and fetal heart rate monitoring in a digital signal controller platform.

An LMS-based algorithm to monitor fetal and maternal heart rate in real time was implemented and evaluated on a development platform. Hardware has three modules: dsPIC30F digital signal controller, a low-noise analog front end and a storage stage. They were evaluated using on-chip debugging tools and a patient simulator.

Effect of considering constant variance time-frequency autoregressive models for HRV analysis.

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.

Baroreflex sensitivity assessment and heart rate variability: relation to maneuver and technique.

In the present study, we examined two baroreflex sensitivity (BRS) issues that remain uncertain: the differences among diverse BRS assessment techniques and the association between BRS and vagal outflow. Accordingly, the electrocardiogram and non-invasive arterial pressure were recorded in 27 healthy subjects, during supine with and without controlled breathing, standing, exercise, and recovery conditions. Vagal outflow was estimated by heart rate variability indexes, whereas BRS was computed by alpha-coefficient, transfer function, complex demodulation in low- and high-frequency bands, and by sequence technique.

Effect of static and dynamic exercise on heart rate and blood pressure variabilities.

Purpose: This study examines the effect of static and dynamic leg exercises on heart rate variability (HRV) and blood pressure variability (BPV) in humans.

Methods: 10 healthy male subjects were studied at rest, during static exercise performed at 30% of maximal voluntary contraction (SX30), and during dynamic cycling exercises done at 30% of VO2max (DX30) and at 60% of VO2max (DX60). Respiration, heart rate, and blood pressure signals were digitized to analyze temporal and spectral parameters involving short and overall indexes (SD, deltaRANGE, RMSSD, Total power), power of the low (LF), middle (MF), and high (HF) frequency components, and the baroreceptor sensitivity by the alphaMF index.

Densitometric validation of nine anthropometric prediction equations of body composition in young native men of Mexico City.

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.