Comparison of various techniques used to estimate spontaneous baroreflex sensitivity (the EuroBaVar study)

2004 ◽  
Vol 286 (1) ◽  
pp. R226-R231 ◽  
Author(s):  
Dominique Laude ◽  
Jean-Luc Elghozi ◽  
Arlette Girard ◽  
Elisabeth Bellard ◽  
Malika Bouhaddi ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Frequency Band ◽  
Baroreflex Sensitivity ◽  
Low Frequency ◽  
The Other ◽  
Data Sets ◽  
Noninvasive Blood Pressure ◽  
Sequence Method ◽  
Baroreflex Failure ◽  
Spontaneous Baroreflex

This study compared spontaneous baroreflex sensitivity (BRS) estimates obtained from an identical set of data by 11 European centers using different methods and procedures. Noninvasive blood pressure (BP) and ECG recordings were obtained in 21 subjects, including 2 subjects with established baroreflex failure. Twenty-one estimates of BRS were obtained by methods including the two main techniques of BRS estimates, i.e., the spectral analysis (11 procedures) and the sequence method (7 procedures) but also one trigonometric regressive spectral analysis method (TRS), one exogenous model with autoregressive input method (X-AR), and one Z method. With subjects in a supine position, BRS estimates obtained with calculations of α-coefficient or gain of the transfer function in both the low-frequency band or high-frequency band, TRS, and sequence methods gave strongly related results. Conversely, weighted gain, X-AR, and Z exhibited lower agreement with all the other techniques. In addition, the use of mean BP instead of systolic BP in the sequence method decreased the relationships with the other estimates. Some procedures were unable to provide results when BRS estimates were expected to be very low in data sets (in patients with established baroreflex failure). The failure to provide BRS values was due to setting of algorithmic parameters too strictly. The discrepancies between procedures show that the choice of parameters and data handling should be considered before BRS estimation. These data are available on the web site ( http://www.cbi.polimi.it/glossary/eurobavar.html ) to allow the comparison of new techniques with this set of results.

Applicability of recent methods used to estimate spontaneous baroreflex sensitivity to resting mice

2008 ◽  
Vol 294 (1) ◽  
pp. R142-R150 ◽  
Author(s):  
Dominique Laude ◽  
Véronique Baudrie ◽  
Jean-Luc Elghozi
Keyword(s):  
Baroreflex Sensitivity ◽  
Low Frequency ◽  
Pulse Interval ◽  
Arterial Baroreflex ◽  
Baroreflex Control ◽  
Spectral Estimates ◽  
Sequence Method ◽  
Highly Correlated ◽  
Spontaneous Baroreflex ◽  
Sequence Techniques

Short-term blood pressure (BP) variability is limited by the arterial baroreflex. Methods for measuring the spontaneous baroreflex sensitivity (BRS) aim to quantify the gain of the transfer function between BP and pulse interval (PI) or the slope of the linear relationship between parallel BP and PI changes. These frequency-domain (spectral) and time-domain (sequence) techniques were tested in conscious mice equipped with telemetric devices. The autonomic relevance of these indexes was evaluated using pharmacological blockades. The significant changes of the spectral bandwidths resulting from the autonomic blockades were used to identify the low-frequency (LF) and high-frequency (HF) zones of interest. The LF gain was 1.45 ± 0.14 ms/mmHg, with a PI delay of 0.5 s. For the HF gain, the average values were 2.0 ± 0.19 ms/mmHg, with a null phase. LF and HF bands were markedly affected by atropine. On the same 51.2-s segments used for cross-spectral analysis, an average number of 26.4 ± 2.2 slopes were detected, and the average slope in resting mice was 4.4 ± 0.5 ms/mmHg. Atropine significantly reduced the slopes of the sequence method. BRS measurements obtained using the sequence technique were highly correlated to the spectral estimates. This study demonstrates the applicability of the recent methods used to estimate spontaneous BRS in mice. There was a vagal predominance in the baroreflex control of heart rate in conscious mice in the present conditions.

scholarly journals Some results of analysis of inverted echo-sounder records from the Atlantic equatorial region

1985 ◽  
Vol 33 (2) ◽  
pp. 213-218
Author(s):  
Alberto dos Santos Franco ◽  
Joseph Harari ◽  
Afrânio Rubens de Mesquita
Keyword(s):  
Spectral Analysis ◽  
Internal Waves ◽  
Frequency Band ◽  
Equatorial Region ◽  
Temperature Series ◽  
The Other ◽  
Tidal Analysis ◽  
Frequency Bands ◽  
Inverted Echo Sounder ◽  
Even Harmonics

The tidal analysis of data from the Equatorial region, given by inverted echo-sounders, show considerable residuals in the frequency band of approximately 2 cycles per day. In the even harmonics of 4 and 6 cycles per day, tidal components statistically not negligible are also identified. Spectral analysis of temperature series from the same area show, on the other hand, variabilities in the same frequency bands, which suggests the occurrence of internal waves with energy distributed in these frequency bands, in the Atlantic Equatorial area.

Spontaneous baroreflex sensitivity after coronary artery bypass graft surgery as a function of gender and age

2003 ◽  
Vol 81 (9) ◽  
pp. 894-902 ◽  
Author(s):  
C Ann Brown ◽  
Larry A Wolfe ◽  
Sylvia Hains ◽  
Glorianne Ropchan ◽  
Joel Parlow
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Spectral Analysis ◽  
Baroreflex Sensitivity ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Artery Bypass Graft ◽  
Standing Posture ◽  
Cabg Surgery ◽  
Spontaneous Baroreflex

The effects of coronary artery bypass graft (CABG) surgery on spontaneous baroreflex (SBR) sensitivity and heart rate variability were examined in 11 women and 23 men preoperatively and 5 days postoperatively. Electrocardiograph R–R interval and beat-by-beat arterial blood pressure data were collected continuously for 20 min in the supine and standing postures. Coarse graining spectral analysis was performed on the heart rate variability data. Spontaneous baroreflex sensitivity declined after surgery with a differential influence of gender. Men showed a decrease in SBR slope following surgery, with a greater decrease in the standing posture; the parasympathetic (PNS) indicator was lower postoperatively and in the standing posture; the reduction in low-frequency (LF) power was greater for the younger men. In women, the PNS indicator was lower in the standing posture. Both men and women showed a decrease in high-frequency power following CABG surgery, which decreased the sensitivity of the short-term cardiac control mechanisms that modulate heart rate, with the greater effects occurring in men. The reduction in SBR sensitivity indicates that the ability of the cardiovascular system to respond rapidly to changing stimuli was compromised. The decline in the PNS indicator implies that patients were vulnerable to the risks of myocardial ischemia, sympathetically mediated cardiac dysrhythmias, and sudden cardiac death.Key words: spectral analysis, spontaneous baroreflex sensitivity, CABG surgery, gender, age, posture.

Experimental Study of Jet Noise Characteristics of Series Connected Nozzles

2005 ◽  
Author(s):  
Qiang Xu
Keyword(s):  
Frequency Spectrum ◽  
Frequency Band ◽  
Low Frequency ◽  
Jet Noise ◽  
Steel Tube ◽  
The Other ◽  
Chamber Pressure ◽  
Band Frequency ◽  
Noise Characteristics ◽  
Frequency Peak

Put abstract text here. A serial of experiments were conducted to study the noise radiated from a series connected nozzle pair. The experiment results are presented in this paper. This nozzle pair consists of two nozzles, one is called source nozzle, and the other is a secondary nozzle. In these experiments, the structure of source nozzle was fixed while that of secondary nozzle was changeable. The source nozzle is mounted on a pressure chamber which is connected to an air compressor. A steel tube is fixed at the tail of source nozzle. The secondary nozzle is connected to the other end of the tube. Throat size of secondary nozzle is larger then that of source nozzle. 15 types of nozzles with different expansion ratio, length of expand segment, and throat structure were used as the secondary nozzle. Jet noise pressure of these nozzle pairs was measured by 40AF Free Field Microphone. The frequency spectrum of jet noise from source nozzle with steel tube under different chamber pressures was calculated. The pressure range is from 0.1 to 1.2 MPa. This result is compared with those spectrums of nozzle pair with different secondary nozzle under different chamber pressures. The trend of peak frequency shifts for different nozzle pair and different chamber pressure is presented in this paper. The secondary nozzles make frequency peak shift from the source nozzle, especially in low frequency band. Different structure of secondary nozzle has different influence on the frequency characteristics of jet noise. Length of expand segment has greater influence on low frequency peak than other two factors. Joint time-frequency analysis is also used in analyze the change of frequency spectrum during throat size decreased under fixed chamber pressure and various spectrograms are also presented. In low frequency band, frequency peak remains during the change of source nozzle throat size. But in higher frequency band, the frequency peak shifts from low frequency to higher ones as the throat size decreases.

Sympathovagal Effects of Spinal Anesthesia Assessed by the Spontaneous Cardiac Baroreflex 

1997 ◽  
Vol 87 (6) ◽  
pp. 1359-1367 ◽  
Author(s):  
P. Gratadour ◽  
J. P. Viale ◽  
J. Parlow ◽  
P. Sagnard ◽  
H. Counioux ◽  
...  
Keyword(s):  
Spinal Anesthesia ◽  
Time Domain ◽  
Baroreflex Sensitivity ◽  
Sensory Block ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Sympathovagal Balance ◽  
Volume Loading ◽  
Noninvasive Blood Pressure ◽  
Spontaneous Baroreflex

Background The changes in sympathovagal balance induced by spinal anesthesia remain controversial. The spontaneous baroreflex method allows the continuous assessment of the spontaneous engagement of the cardiac baroreflex, giving an index of sympathovagal balance. The purpose of this study was to follow the effects of spinal anesthesia on spontaneous baroreflex sensitivity. Methods Continuous electrocardiogram and noninvasive blood pressure were recorded in 24 patients scheduled for elective inguinal hernia repair and randomly assigned to three groups: (1) no volume loading, (2) volume loading of 15 ml/kg lactated Ringer's solution, and (3) continuous infusion of etilefrine (an ephedrine-like drug). Each patient was studied before, during, and after bupivacaine-induced spinal anesthesia (mean sensory block: T4). Spontaneous baroreflex sensitivity and parameters of time-domain analysis of heart rate variability were calculated from 30 min of recording of each period. Results No significant change in spontaneous baroreflex slope or parameters of time-domain analysis were observed after regional anesthesia in any group. However, three patients experienced episodes of bradycardia and hypotension in the absence of a high block; these three patients showed an increase in spontaneous baroreflex sensitivity and time-domain parameters. Conclusions Using a noninvasive, continuous technique to estimate cardiac sympathovagal balance, no significant variation in autonomic balance induced by spinal anesthesia was observed. However, untoward episodes of bradycardia and hypotension occurred in three patients, who could not be prospectively identified by the parameters studied.

Measuring baroreflex sensitivity from the gain function between arterial pressure and heart period

2002 ◽  
Vol 103 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Gian Domenico PINNA ◽  
Roberto MAESTRI ◽  
Grzegorz RACZAK ◽  
Maria Teresa LA ROVERE
Keyword(s):  
Arterial Pressure ◽  
Frequency Band ◽  
Baroreflex Sensitivity ◽  
Low Frequency ◽  
Systolic Arterial Pressure ◽  
Normal Subjects ◽  
Heart Period ◽  
Gain Function ◽  
Limits Of Agreement ◽  
Spectral Technique

We tested an innovative approach for estimating baroreflex sensitivity (BRS) from the gain function between spontaneous oscillations of systolic arterial pressure (SAP) and heart period (HP). The major goal was to assess the practical implications of abandoning the classical coherence criterion (⩾0.5) as regards measurability of BRS, and agreement with values of BRS obtained using the phenylephrine test (Phe-BRS). We studied 19 normal subjects, 44 patients with a history of previous myocardial infarction (MI) and 45 patients with chronic heart failure (CHF). The experimental protocol included recording of SAP and HP for 10min of supine rest, and evaluation of Phe-BRS. From resting SAP and HP, the gain and coherence functions were computed. The new BRS index was obtained in all subjects by averaging the gain function over the whole low-frequency band (0.04-0.15Hz) (whole-band average BRS, WBA-BRS). WBA-BRS was 7.4 (5.8-10.8)ms/mmHg [median (25th-75th percentile)] in normal controls, 3.1 (1.4-5.4)ms/mmHg in MI patients (P<0.001 compared with normals) and 5.0 (3.2-6.9)ms/mmHg in CHF patients (P<0.01 compared with normals). Using the coherence criterion, BRS could be measured in only 43% and 49% of MI and CHF patients respectively, and the proportion of the low-frequency band contributing to the measurement was 21% (14-47%) and 29% (16-35%) respectively. The correlation between WBA-BRS and Phe-BRS was 0.47, 0.63 and 0.36 in the normal, MI and CHF groups respectively (all P<0.001). The relative bias of WBA-BRS was -5.2ms/mmHg (P<0.001) in normals, -1.4ms/mmHg (P = 0.004) in MI patients and -1.0ms/mmHg (P = 0.11) in CHF patients. The limits of agreement were -13 to 2.6, -7.4 to 4.6 and -9.3 to 7.3ms/mmHg in the normal, MI and CHF groups respectively. Thus the WBA-BRS method standardizes the computation of BRS among subjects, and dramatically increases its measurability in subjects with pathology compared with the classical spectral technique based on the coherence criterion. Compared with Phe-BRS, WBA-BRS tends to give negatively biased results. The correlation and the magnitude of the limits of agreement between the two methods are similar to those observed previously using coherence-based spectral methods.

Hemodynamic and autonomic correlates of postexercise hypotension in patients with mild hypertension

2002 ◽  
Vol 282 (4) ◽  
pp. R1037-R1043 ◽  
Author(s):  
Jacopo M. Legramante ◽  
Alberto Galante ◽  
Michele Massaro ◽  
Antonio Attanasio ◽  
Gianfranco Raimondi ◽  
...  
Keyword(s):  
Baroreflex Sensitivity ◽  
Autonomic Function ◽  
Peripheral Resistance ◽  
Low Frequency ◽  
Arterial Baroreflex ◽  
Aged Patients ◽  
Before And After ◽  
Cardiac Component ◽  
Postexercise Hypotension ◽  
Spontaneous Baroreflex

We investigated the interplay of neural and hemodynamic mechanisms in postexercise hypotension (PEH) in hypertension. In 15 middle-aged patients with mild essential hypertension, we evaluated blood pressure (BP), cardiac output (CO), total peripheral resistance (TPR), forearm (FVR) and calf vascular resistance (CVR), and autonomic function [by spectral analysis of R-R interval and BP variabilities and spontaneous baroreflex sensitivity (BRS)] before and after maximal exercise. Systolic and diastolic BP, TPR, and CVR were significantly reduced from baseline 60–90 min after exercise. CO, FVR, and HR were unchanged. The low-frequency (LF) component of BP variability increased significantly after exercise, whereas the LF component of R-R interval variability was unchanged. The overall change in BRS was not significant after exercise vs. baseline, although a significant, albeit small, BRS increase occurred in response to hypotensive stimuli. These findings indicate that in hypertensive patients, PEH is mediated mainly by a peripheral vasodilation, which may involve metabolic factors linked to postexercise hyperemia in the active limbs. The vasodilator effect appears to override a concomitant, reflex sympathetic activation selectively directed to the vasculature, possibly aimed to counter excessive BP decreases. The cardiac component of arterial baroreflex is reset during PEH, although the baroreflex mechanisms controlling heart period appear to retain the potential for greater opposition to hypotensive stimuli.

scholarly journals Artifacts in dependency structures of Portapres® signals

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Marko Mozetić ◽  
Tamara Škorić ◽  
Jelena Antelj ◽  
Katarina Otašević ◽  
Branislav Milovanović ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Baroreflex Sensitivity ◽  
Pulse Interval ◽  
Signal Acquisition ◽  
Non Invasive ◽  
Complex Procedure ◽  
Sequence Method ◽  
Copula Density ◽  
Spontaneous Baroreflex ◽  
Dependency Structures

Portapres® is a unique device that reliably accomplishes a challenging task of continuous and non-invasive recording ofblood pressure (BP) waveforms in moving subjects. The complex procedure of Portapres® signal acquisition includes periodic changesof cuffed fingers to avoid pain and stress, as well as the blood pressure correction due to the increasing and decreasing elevation of armposture. Due to these procedures, the recorded waveforms are corrupted. The aim of this paper is to analyze the influence of inevitableartifacts on parameters obtained from the blood pressure waveforms. The analyzed waveforms are obtained from healthy volunteers atBezanija Kosa Hospital, Belgrade. The parameters include systolic blood pressure (SBP) and pulse interval (PI) extracted byBeatscope® software. The interrelationship of SBP and PI signals forms a major cardiovascular feedback – baroreflex. It can beanalyzed using the sequence method for spontaneous baroreflex sensitivity, but the tools that reveal more profound dependencystructures include cross-approximate and cross-sample entropy, as well as the copula structures. The influence of artifacts, inevitable inPortapres® signals, is the main goal of this study. The analyses revealed that automatic artifact correction induced no significantchanges considering the statistical moments and the baroreflex sensitivity; the same applies to the copula density and rank tests. Theentropy analysis, however, turned out to be extremely sensitive so its implementation in Portapres® signal analysis is not recommended.

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