Frequency-domain characteristics and filtering of blood flow following the onset of exercise: implications for kinetics analysis

2006 ◽  
Vol 100 (3) ◽  
pp. 817-825 ◽  
Author(s):  
Leonardo F. Ferreira ◽  
Allison J. Harper ◽  
Thomas J. Barstow
Keyword(s):  
Blood Flow ◽  
Power Spectrum ◽  
Time Constant ◽  
Standard Error ◽  
Phase 1 ◽  
High Signal ◽  
Parameter Estimates ◽  
Phase 2 ◽  
Pass Filter ◽  
Low Pass Filter

We examined the validity and usefulness of a low-pass filter (LPFILTER) to reduce point-to-point variability and enhance parameter estimation of the kinetics of blood flow (BF). Computer simulations were used to determine the power spectrum of simulated responses. Moreover, we studied the leg BF response to a single transition in four subjects during supine knee-extension exercise using three methods of data processing [beat-by-beat, average of 3 cardiac cycles (AVG3 BEATS), and LPFILTER]. The power spectrum of BF containing the kinetics information (≤0.2 Hz) did not overlap with the oscillations due to muscle contraction and cardiac cycle (simulations and Doppler measurements). There were no significant differences between the parameter estimates for a two-exponential model using Beat-by-Beat, AVG3 BEATS, and LPFILTER ( P > 0.05; n = 4). However, LPFILTER (cutoff = 0.2 Hz) resulted in a significantly lower standard error of the estimate for all parameters ( P < 0.05). The means ± SD for the standard error of the estimate for Beat-by-Beat, AVG3 BEATS, and LPFILTER were, respectively, time constant- phase 1 = 5.0 ± 1.1 s, 4.5 ± 2.1 s, and 0.3 ± 0.2 s; time delay- phase 2 = 17.8 ± 7.9 s, 12.8 ± 7.5 s, and 1.4 ± 1.4 s; time constant- phase 2 = 15.8 ± 4.6 s, 9.9 ± 2.9 s, and 1.1 ± 0.5 s. In conclusion, LPFILTER appeared to be a valid procedure providing a high signal-to-noise ratio and data density and thus LPFILTER resulted in the smallest confidence interval for parameter estimates of BF kinetics.

Dose-dependent thrombus resolution due to oral plasminogen activator inhibitor (PAI)-1 inhibition with tiplaxtinin in a rat stenosis model of venous thrombosis

2008 ◽  
Vol 99 (04) ◽  
pp. 749-758 ◽  
Author(s):  
Sanjiv Baxi ◽  
David Crandall ◽  
Thomas Meier ◽  
Shirley Wrobleski ◽  
Angela Hawley ◽  
...  
Keyword(s):  
Blood Flow ◽  
Inferior Vena Cava ◽  
Venous Thrombosis ◽  
Inferior Vena ◽  
Phase 1 ◽  
Vena Cava ◽  
Phase 2 ◽  
Oral Gavage ◽  
Dose Dependent ◽  
Pai 1

SummaryThis study aimed to evaluate a small-molecule PAI-1 inhibitor (PAI-039; tiplaxtinin) in a rodent stenosis model of venous thrombosis in a two-phase experiment. Phase 1 determined the efficacy of tiplaxtinin against Lovenox (LOV), while phase 2 determined the dose-dependent efficacy. For both phases, drug treatment began 24 hours after surgically induced venous thrombosis and continued for four days. Phase 1 animals (n = 24) receiving low-dose (LD; 1 mg/kg oral gavage) PAI-1 inhibitor demonstrated a 52% decrease in thrombus weight (TW) versus controls (p < 0.05) with significant reductions in active plasma PAI-1, while the high-dose (HD; 10 mg/kg oral gavage) group demonstrated a 23% reduction in TW versus controls. Animals treated subcutaneously with LOV (3 mg/kg) showed a 39% decrease in TW versus controls (p < 0.05). Coagulation tests (aPTT and TCT) were significantly different in LOV compared to PAI-1 inhibitor groups. PAI-039 treatment was also associated with significantly increased return of inferior vena cava blood flow four days post-thrombosis versus controls (p < 0.05). In phase 2 (n = 30), TW was reduced from the 0.5 mg/kg to 5 mg/ kg experimental groups, with the 10 mg/kg group demonstrating a paradoxical increase. The 5 mg/kg group showed statistically significant decreases in TW versus controls after four treatment days (p < 0.05). This is the first study to demonstrate dose related effects of PAI-039 on increasing thrombus resolution and inferior vena cava blood flow without adverse effects on anti-coagulation in a rat stenosis model of venous thrombosis.

scholarly journals Noise Reduction Analysis of Radar Rainfall Using Chaotic Dynamics and Filtering Techniques

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Soojun Kim ◽  
Huiseong Noh ◽  
Narae Kang ◽  
Keonhaeng Lee ◽  
Yonsoo Kim ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Correlation Coefficient ◽  
Standard Error ◽  
Rainfall Series ◽  
Radar Rainfall ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Filtering Technique ◽  
Filtering Techniques

The aim of this study is to evaluate the filtering techniques which can remove the noise involved in the time series. For this, Logistic series which is chaotic series and radar rainfall series are used for the evaluation of low-pass filter (LF) and Kalman filter (KF). The noise is added to Logistic series by considering noise level and the noise added series is filtered by LF and KF for the noise reduction. The analysis for the evaluation of LF and KF techniques is performed by the correlation coefficient, standard error, the attractor, and the BDS statistic from chaos theory. The analysis result for Logistic series clearly showed that KF is better tool than LF for removing the noise. Also, we used the radar rainfall series for evaluating the noise reduction capabilities of LF and KF. In this case, it was difficult to distinguish which filtering technique is better way for noise reduction when the typical statistics such as correlation coefficient and standard error were used. However, when the attractor and the BDS statistic were used for evaluating LF and KF, we could clearly identify that KF is better than LF.

scholarly journals Dynamic relationship between sympathetic nerve activity and renal blood flow: a frequency domain approach

2001 ◽  
Vol 281 (1) ◽  
pp. R206-R212 ◽  
Author(s):  
Sarah-Jane Guild ◽  
Paul C. Austin ◽  
Michael Navakatikyan ◽  
John V. Ringwood ◽  
Simon C. Malpas
Keyword(s):  
Blood Flow ◽  
Transfer Function ◽  
Renal Blood Flow ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Nerve Activity ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Dynamic Relationship ◽  
Transfer Function Analysis

Blood pressure displays an oscillation at 0.1 Hz in humans that is well established to be due to oscillations in sympathetic nerve activity (SNA). However, the mechanisms that control the strength or frequency of this oscillation are poorly understood. The aim of the present study was to define the dynamic relationship between SNA and the vasculature. The sympathetic nerves to the kidney were electrically stimulated in six pentobarbital-sodium anesthetized rabbits, and the renal blood flow response was recorded. A pseudo-random binary sequence (PRBS) was applied to the renal nerves, which contains equal spectral power at frequencies in the range of interest (<1 Hz). Transfer function analysis revealed a complex system composed of low-pass filter characteristics but also with regions of constant gain. A model was developed that accounted for this relationship composed of a 2 zero/4 pole transfer function. Although the position of the poles and zeros varied among animals, the model structure was consistent. We also found the time delay between the stimulus and the RBF responses to be consistent among animals (mean 672 ± 22 ms). We propose that the identification of the precise relationship between SNA and renal blood flow (RBF) is a fundamental and necessary step toward understanding the interaction between SNA and other physiological mediators of RBF.

Application of IMC-PID in the Hydraulic Headbox Total Pressure Control

2012 ◽  
Vol 462 ◽  
pp. 789-795
Author(s):  
Wei Tang ◽  
Xu Zhong Niu ◽  
Wen Juan Shan
Keyword(s):  
Control System ◽  
Time Constant ◽  
Total Pressure ◽  
Pressure Control ◽  
Internal Model Control ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Model Control ◽  
Low Pass ◽  
Pressure Control System

It is very difficult to obtain perfect performance to apply the conventional PID (Proportional-Integral-Derivative) controller, because hydraulic headbox needs high precision total pressure control. Transfer function of total pressure control system was identified by using the direct identification method which is based on the least square method for the first-order plus delay time model. Then combined with IMC (Internal-Model-control) –PID method, an IMC-PID controller was designed, which is simple and only needed to adjust one parameter-the time constant of low pass filter. Acceptable performance can also be obtained by tuning time constant of the low pass filter when the model doesn't match with the real process. The algorithm was applied to total pressure control system of hydraulic headbox. Simulation and practical application show that, IMC-PID is of strong robustness and good dynamic characteristics. Finally, the control system is implemented by S7-300 PLC.

Blunted Hyperemic Response to Mental Stress in Young, Non-Hispanic Black Men is not Impacted by Acute Dietary Nitrate Supplementation

2021 ◽  
Author(s):  
John D. Akins ◽  
Bryon M. Curtis ◽  
Jordan C. Patik ◽  
Guillermo Olvera ◽  
Aida Nasirian ◽  
...  
Keyword(s):  
Blood Flow ◽  
Vascular Function ◽  
Mental Stress ◽  
Forearm Blood Flow ◽  
Phase 1 ◽  
Nitrate Content ◽  
Phase 2 ◽  
Dietary Nitrate ◽  
Nitrate Supplementation ◽  
No Bioavailability

Non-Hispanic black individuals have an elevated prevalence of cardiovascular disease in large part, related to impaired vascular function, secondary to reduced nitric oxide (NO) bioavailability. Nitrate supplementation increases NO bioavailability and improves vascular function. This study tested the hypothesis that forearm blood flow responses in young, non-Hispanic, black (BL) men during mental stress are blunted relative to, non-Hispanic, white (WH) men and that acute dietary nitrate supplementation would improve this response in BL men. This study was comprised of two parts. Phase 1 investigated the blood flow responses between young, BL and WH men whereas Phase 2 investigated the effect of acute nitrate supplementation in a subset of the BL men. Eleven (9 for Phase 2) BL and 8 WH men (23 ± 3 vs. 24 ± 4 y, respectively) participated. During each visit, brachial artery blood flow was assessed during 3 min of mental stress. Phase 1 was completed in one visit, while Phase 2 was completed over two visits separated by ~1-wk. During Phase 2, data were collected before and 2-h post-consumption of a beverage high in nitrate content or nitrate depleted. In Phase 1, peak forearm blood flow (FBF, P < 0.01), total FBF (P < 0.05), and forearm vascular conductance (P < 0.001) were blunted in the BL. During Phase 2, pre-beverage responses were unaffected following beverage consumption (P > 0.05 for all). Young, BL men have blunted microvascular vasodilatory responses to acute mental stress, which may not be altered following acute nitrate supplementation.

Simulation of pulmonary O2 uptake during exercise transients in humans

1987 ◽  
Vol 63 (6) ◽  
pp. 2253-2261 ◽  
Author(s):  
T. J. Barstow ◽  
P. A. Mole
Keyword(s):  
Blood Flow ◽  
Phase 1 ◽  
Muscle Metabolism ◽  
Exponential Model ◽  
Model Parameters ◽  
Second Phase ◽  
Phase 2 ◽  
O2 Uptake ◽  
Vo2 Kinetics ◽  
Kinetics Of

Computer simulation of blood flow and O2 consumption (QO2) of leg muscles and of blood flow through other vascular compartments was made to estimate the potential effects of circulatory adjustments to moderate leg exercise on pulmonary O2 uptake (VO2) kinetics in humans. The model revealed a biphasic rise in pulmonary VO2 after the onset of constant-load exercise. The length of the first phase represented a circulatory transit time from the contracting muscles to the lung. The duration and magnitude of rise in VO2 during phase 1 were determined solely by the rate of rise in venous return and by the venous volume separating the muscle from the lung gas exchange sites. The second phase of VO2 represented increased muscle metabolism (QO2) of exercise. With the use of a single-exponential model for muscle QO2 and physiological estimates of other model parameters, phase 2 VO2 could be well described as a first-order exponential whose time constant was within 2 s of that for muscle QO2. The use of unphysiological estimates for certain parameters led to responses for VO2 during phase 2 that were qualitatively different from QO2. It is concluded that 1) the normal response of VO2 in humans to step increases in muscle work contains two components or phases, the first determined by cardiovascular phenomena and the second primarily reflecting muscle metabolism and 2) the kinetics of VO2 during phase 2 can be used to estimate the kinetics of muscle QO2. The simulation results are consistent with previously published profiles of VO2 kinetics for square-wave transients.

V˙o 2 kinetics reveal a central limitation at the onset of subthreshold exercise in heart transplant recipients

2000 ◽  
Vol 88 (4) ◽  
pp. 1228-1238 ◽  
Author(s):  
Bertrand Mettauer ◽  
Quan Ming Zhao ◽  
Eric Epailly ◽  
Anne Charloux ◽  
Eliane Lampert ◽  
...  
Keyword(s):  
Time Constant ◽  
Heart Transplant ◽  
Ventilatory Threshold ◽  
Phase 1 ◽  
Phase 2 ◽  
Transplant Recipients ◽  
Lower Phase ◽  
Group Time ◽  
Heart Transplant Recipients ◽  
Muscular Metabolism

Because the cardiocirculatory response of heart transplant recipients (HTR) to exercise is delayed, we hypothesized that their O2 uptake (V˙o 2) kinetics at the onset of subthreshold exercise are slowed because of an impaired early “cardiodynamic” phase 1, rather than an abnormal subsequent “metabolic” phase 2. Thus we compared the V˙o 2 kinetics in 10 HTR submitted to six identical 10-min square-wave exercises set at 75% (36 ± 5 W) of the load at their ventilatory threshold (VT) to those of 10 controls (C) similarly exercising at the same absolute (40 W; C40W group) and relative load (67 ± 14 W; C67W group). Time-averaged heart rate, breath-by-breathV˙o 2, and O2pulse (O2p) data yielded monoexponential time constants of the V˙o 2 (s) and O2p increase. Separating phase 1 and 2 data permitted assessment of the phase 1 duration and phase 2 V˙o 2 time constant ([Formula: see text]). The V˙o 2 time constant was higher in HTR (38.4 ± 7.5) than in C40W (22.9 ± 9.6; P ≤ 0.002) or C67W (30.8 ± 8.2; P ≤ 0.05), as was the O2p time constant, resulting from a lower phase 1V˙o 2 increase (287 ± 59 vs. 349 ± 66 ml/min; P ≤ 0.05), O2p increase (2.8 ± 0.6 vs. 3.6 ± 1.0 ml/beat; P ≤ 0.0001), and a longer phase 1 duration (36.7 ± 12.3 vs. 26.8 ± 6.0 s; P≤ 0.05), whereas the[Formula: see text]was similar in HTR and C (31.4 ± 9.6 vs. 29.9 ± 5.6 s; P = 0.85). Thus the HTR have slower subthresholdV˙o 2 kinetics due to an abnormal phase 1, suggesting that the heart is unable to increase its output abruptly when exercise begins. We expected a faster[Formula: see text]in HTR because of their prolonged phase 1 duration. Because this was not the case, their muscular metabolism may also be impaired at the onset of subthreshold exercise.

scholarly journals The speed of the hair cell mechanotransducer channel revealed by fluctuation analysis

2021 ◽  
Vol 153 (10) ◽  
Author(s):  
Maryline Beurg ◽  
Jong-Hoon Nam ◽  
Robert Fettiplace
Keyword(s):  
Time Constant ◽  
Single Channel ◽  
Noise Analysis ◽  
Outer Hair Cells ◽  
Fluctuation Analysis ◽  
Molecular Architecture ◽  
Activation Time ◽  
Channel Conductance ◽  
Pass Filter ◽  
Low Pass Filter

Although mechanoelectrical transducer (MET) channels have been extensively studied, uncertainty persists about their molecular architecture and single-channel conductance. We made electrical measurements from mouse cochlear outer hair cells (OHCs) to reexamine the MET channel conductance comparing two different methods. Analysis of fluctuations in the macroscopic currents showed that the channel conductance in apical OHCs determined from nonstationary noise analysis was about half that of single-channel events recorded after tip link destruction. We hypothesized that this difference reflects a bandwidth limitation in the noise analysis, which we tested by simulations of stochastic fluctuations in modeled channels. Modeling indicated that the unitary conductance depended on the relative values of the channel activation time constant and the applied low-pass filter frequency. The modeling enabled the activation time constant of the channel to be estimated for the first time, yielding a value of only a few microseconds. We found that the channel conductance, assayed with both noise and recording of single-channel events, was reduced by a third in a new deafness mutant, Tmc1 p.D528N. Our results indicate that noise analysis is likely to underestimate MET channel amplitude, which is better characterized from recordings of single-channel events.

Sign in / Sign up

Export Citation Format

Share Document