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Results 451 - 500 of 644
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Yanagihashi R - - 1997
The psycho-physiological effects of several sound stimulations were investigated to evaluate the relationship between a psychological parameter, such as subjective perception, and a physiological parameter, such as the heart rate variability (HRV). Eight female students aged 21-22 years old were tested. Electrocardiogram (ECG) and the movement of the chest-wall for ...
Tamura T - - 1997
An ambulatory acceleration monitor was developed and used to evaluate physical activity in the elderly. The ECG and accelerations at the wrist, waist, and ankle were recorded, and the heart rate and frequency and amplitude of accelerations per unit time were evaluated in both working and retired elderly women performing ...
Thayer J F - - 1997
High heart rate variability (HRV) has been associated with more efficient autonomic control, allowing more responsivity and sensitivity to changing environmental demands. A number of specific periodicities have been identified in the spectra of cardiac time series. A high frequency component related to respiratory sinus arrhythmia, a low frequency component ...
Valenta H L HL - - 1997
High power ultrasonic transducers for medical surgery require closed loop regulation of operating frequency and amplitude. This is a tutorial design paper which provides a description of the fundamental component properties and the criteria which are required to drive a power ultrasonic transducer. In addition, a classical root locus system ...
Keselbrener L - - 1996
In this study, the selective windowed discrete Fourier transform algorithm (SDA) for time-frequency analysis was applied on non-stationary heart rate signals, recorded during vagal perturbations. These perturbations were achieved in healthy subjects (aged 6-42 years) by inducing the oculocardiac reflex and the diving response. The results showed that the SDA ...
Kroll D J - - 1996
Interobserver reproducibility is high for time domain and power spectral measures of heart rate variability, with greater reproducibility for low-frequency measures, and especially for the standard deviation of the 5-minute RR intervals over 24 hours, than for high-frequency measures. Overall interobserver variability of < 8% for these measures is largely ...
Patzak A - - 1996
Postnatal adaptation should be associated with changes in cardiac rhythmic behavior. To examine the development of heart rate variability, instantaneous heart rate (IHR) and the corresponding breathing signals of 16 healthy infants were analyzed. This was pursued by use of fast Fourier transformation beginning with the 1st day until the ...
Sava H P - - 1996
This paper demonstrates an improvement in the performance of spectral phonocardiography, combined with pattern recognition techniques for monitoring the condition of bioprosthetic heart valves. The analysis of the heart sounds is performed using a modified forward-backward overdetermined Prony's method. Results show that the condition of the bioprosthesis affects mostly the ...
Kuwahara M - - 1996
We studied power spectral analysis of heart rate (HR) variability in the horse, with the hypothesis that the quantitative information provided by the spectral analysis of HR variability reflects the interaction between sympathetic and parasympathetic regulatory activities. For this purpose, electrocardiogram, blood pressure (BP) and respiratory (Resp) waveform were simultaneously ...
Keselbrener L - - 1996
The Selective Discrete Fourier transform (DFT) Algorithm [SDA] method for the calculation and display of time-frequency distribution has been developed and validated. For each time and frequency, the algorithm selects the shortest required trace length and calculates the corresponding spectral component by means of DFT. This approach can be extended ...
Akay M - - 1996
During hypoxic gasping, the phrenic neurogram (PN) has a steeper rate of rise, an augmented amplitude, and a shorter duration than is seen during eupnea. Because hypoxia reduces neuronal activity, we hypothesized that gasping would be characterized in the frequency domain by enhanced low-frequency power compared with eupnea. Autoregressive (AR) ...
Cleland B G - - 1996
A model is developed that allows evaluation of the pacing efficacy of different stimulus waveforms. It treats the heart as having a first order time constant and enables ready visualization of the time course of the effective voltage within the heart. For pacemakers, where the stimulus pulse is produced by ...
Kawada T - - 1996
Although the characteristics of the static interaction between the sympathetic and parasympathetic nervous systems in regulating heart rate (HR) have been well established, how the dynamic interaction modulates the HR response remains unknown. We therefore investigated dynamic interaction by estimating the transfer function from nerve stimulation to HR using a ...
Friedman B H - - 1996
Spectral analysis of heart period variability was used to examine autonomic cardiac control in several tasks used in experimental and clinical assessments of autonomic nervous system function. Cardiovascular measures were recorded in healthy humans during quiet rest, reaction time shock-avoidance, cold face stress, and combined shock-avoidance/cold face stress. Shock-avoidance was ...
Kobayashi H - - 1996
Heart rate variations during steady state respiration with various frequencies were studied on seven healthy male students at two different body positions. Respiration was controlled at four different frequencies (0.083, 0.100, 0.200, 0.250Hz), and the tidal volume was simultaneously controlled at 1500ml (0.083, 0.100Hz) or 1000ml (0.200, 0.250Hz). A tilting ...
Fleisher L A - - 1996
1. Heart rate variability is modulated by multiple control systems, including autonomic and hormonal systems. Long-term variability, i.e. the very low-frequency band of the power spectra, has been postulated to reflect thermoregulatory vasomotor control, based upon thermal entrainment experiments. However, the relationship between thermoregulatory responses (vasoconstriction and shivering) and heart ...
Kamal A - - 1996
The assessment of autonomic nervous systems (sympathetic and parasympathetic) using the method of complex demodulation and posture entrainment are presented. The heart rate variability signals were derived from the ECG of normal subjects and diabetic patients in both supine and standing positions. The method of complex demodulation is employed on ...
Sapoznikov D - - 1995
Regularity or complexity characteristics of RR interval variations have attained importance in the evaluation of a variety of pathological conditions. Regular periodic fluctuations in heart rate are considered indicators of loss of control in the cardiovascular system and of disturbances in pulmonary function. Methods to detect such loss of cardiopulmonary ...
Petretta M - - 1995
For quantitative assessment of cardiac autonomic control, time and frequency domain measures of heart period variability were calculated by 24 h Holter recording in 10 young obese women with early-onset familial obesity and in 10 control subjects. Ultra low frequency and very low frequency power were lower in obese subjects ...
Hedman A E - - 1995
This study was designed to evaluate the effect of modulating cardiac parasympathetic input on the high frequency component of heart rate variability. We stimulated the right vagus nerve with three different stimulation patterns in anaesthetized, vagotomized and spinal anaesthetized dogs. We kept the mean stimulation frequency constant; controlled the amplitude ...
Kamalesh M - - 1995
Before heart rate variability (HRV) can be used to investigate the effects of drugs or other clinical interventions in chronic stable angina, it is important to establish the stability and reproducibility of HRV indices over time. HRV analysis was performed on two consecutive 24-hour ambulatory ECG recordings in 19 patients ...
Sleigh J W - - 1995
Power spectral analysis of heart rate variability has been used to gain some understanding of the activity of the autonomic nervous system. In this study various indices of heart rate variability were related to the degree of preoperative anxiety experienced by 32 patients presenting for day case surgery. It was ...
Tombros S - - 1995
Every aspect of cardiac function such as contractibility, depolarization and repolarization of cardiac cells, firing rate of pacemaker cells, is under a complex neurohumoral regulation. Especially the autonomic neuron system through the interplay of its two opposing components, sympathetic and parasympathetic (vagal), is controlling cardiac function on a beat to ...
Hedman A E - - 1995
Changes in the function of the autonomic nervous system underlying changes in heart rate variability are not fully understood. Furthermore, decreased heart rate variability has been found to be related to poor prognosis, for example, in patients with coronary artery disease. Our aim was to study how modulation in sympathetic ...
Pieske B - - 1995
BACKGROUND: The present study was performed to test the hypothesis that the altered force-frequency relation in human failing dilated cardiomyopathy may be attributed to alterations in intracellular calcium handling. METHODS AND RESULTS: The force-frequency relation was investigated in isometrically contracting ventricular muscle strip preparations from 5 nonfailing human hearts and ...
Burguera M - - 1995
A new method for the analysis of 24-hour heart rate variability (HRV) using complex demodulation (CDM) implemented with the fast Fourier transform (FFT) and its inverse is described. In a control group with palpitations and dizzy spells (n = 30, 47.2 +/- 16.7 years) the relationship between HRV parameters and ...
Deuschl Gunther - - 1995
The separation between physiologic tremor (PT) in normal subjects and the pathological tremors of essential tremor (ET) or Parkinson's disease (PD) was investigated on the basis of monoaxial accelerometric recordings of 35 s hand tremor epochs. Frequency and amplitude were insufficient to separate between these conditions, except for the trivial ...
Semmler J G JG Department of Physiology, University of Adelaide, - - 1995
Discharge properties of motor units (MUs) in the first dorsal interosseous muscle (FDI) were studied in the dominant and non-dominant hands of six right-handed (RH) and six left-handed (LH) individuals. MU discharge rates and variability were similar in each hand in RH (186 MUs) and LH (160 MUs) subjects. MU ...
Durand L G - - 1995
The objective of the present paper is to provide a detailed review of the most recent developments in instrumentation and signal processing of digital phonocardiography and heart auscultation. After a short introduction, the paper presents a brief history of heart auscultation and phonocardiography, which is followed by a summary of ...
Hayano J - - 1994
A complex demodulation (CDM) method for continuous assessment of frequency shifts and time-dependent changes in amplitude in the rhythmic components existing in predefined frequency bands was proposed and applied to the analysis of high-frequency (HF) and low-frequency (LF) components of the R-R interval and to the analysis of respiration via ...
Elble R J - - 1994
Quantitative electromyography (EMG) and triaxial accelerometry were used to measure hand tremor, finger tremor, and forearm motor unit activity in 36 men and 23 women with essential tremor. Hand tremor was studied with and without 300-g mass loading. Tremor and EMG were recorded twice, with a 3-min rest interval, to ...
Montano N - - 1994
BACKGROUND: The powers of the low-frequency (LF) and high-frequency (HF) oscillations characterizing heart rate variability (HRV) appear to reflect, in their reciprocal relationship, changes in the state of the sympathovagal balance occurring during numerous physiological and pathophysiological conditions. However, no adequate information is available on the quantitative resolution of this ...
Gallasch E - - 1994
To determine whether long and short time exposure of man in 0g alters normal physiological tremor patterns we recorded arm tremor using an accelerometer as well as hand forces and tremor during constant isometric contraction using a load cell. Arm tremor was decreased during both flights in amplitude and frequency. ...
Zernikow B - - 1994
The low frequency cerebral blood flow velocity (CBFV) oscillations in neonates are commonly attributed to an under-dampened immature linear type cerebral autoregulation, and the 'instability' is regarded as causative for peri-intraventricular haemorrhage/periventricular leukomalacia. In contrast, oscillations susceptible to frequency entrainment are a fundamental part of the stable function of non-linear ...
Sakakibara M - - 1994
To examine the hypothesis that the relaxation response is associated with an increase in cardiac parasympathetic tone, the frequency components of heart rate variability during relaxation training were investigated in 16 college students. Electrocardiograms and pneumograms were recorded during a 5-min baseline period followed by three successive 5-min sessions of ...
Malliani A - - 1994
Power spectral analysis of heart period (R-R) and arterial pressure short-term variability reveals the existence of two rhythmic oscillations: a high frequency (HF) component corresponding to respiratory activity (around 0.25 Hz) and a low frequency (LF) component corresponding to vasomotor waves (around 0.10 Hz). Further, a very low frequency (VLF) ...
DeBenedittis G - - 1994
Spectral analysis of beat-to-beat variability in electrocardiography is a simple, noninvasive method to analyze sympatho-vagal interaction. The electrocardiogram is analyzed by means of an automatic, autoregressive modeling algorithm that provides a quantitative estimate of R-R interval variability by the computation of power spectral density. Two major peaks are recognizable in ...
Viitasalo J T - - 1994
Forearm tremor was studied during a spring (stiffness 1090 N.m-1), a rigid isometric and a "dynamic" isometric (carrying a freely hanging mass) loading at the level of 50% of maximal isometric voluntary contraction. Thirteen physical education students ranging in age between 20 and 28 years flexed their dominant forearm isometrically ...
Varghese M A - - 1994
A simple and rapid method of determining occupational workload among Indian women performing manual activities was developed based on the strong relationship between physiological responses and subjective feeling of exertion. A modified five point scale of perceived exertion, sequentially numbered 1 to 5, was created to simplify the complicated and ...
Fan S Z SZ Department of Anesthesiology, National Taiwan University Hospital, Taipei, - - 1994
Fluctuations in heart rate (HR) and arterial blood pressure occurring at respiratory and lower frequencies have long been recognized. However, their significance remained obscure until the monitoring of fetal heart-rate variability (HRV) was appreciated. Recent studies suggest that HRV may reflect the sympatho-vagal interactions that modulate cardiovascular function. Analysis of ...
Ichimaru Y - - 1994
We have developed a system to analyze heart rate variability (HRV) (power spectral array of the HRV) during 24 h ambulatory electrocardiographic monitoring. Several rhythms (circadian and several ultradian rhythms) were observed in the power spectral array of the heart rates and 1/f-like fluctuations in the log-log scaled heart rate ...
Jaffe R S - - 1994
Heart rate variability spectrum analysis provides useful quantitative indices of neural control of the SA node. This method is attractive both for its simplicity and the lack of invasive instrumentation, particularly for human investigation. The differing spectral characteristics of parasympathetic and sympathetic control of heart rate allows separate measurement. However, ...
Sapoznikov D - - 1993
Two methodological aspects of heart rate variability (HRV) are tested. Heart rate variability and RR interval variability (RRV) are compared in 109 healthy subjects using 24-h Holter recordings. Autoregressive power spectrum analysis was performed, and the power in three frequency bands was evaluated by two different methods: the peak power ...
Lui P W - - 1993
We have studied the frequency spectrum of embolic heart sounds as detected by precordial Doppler ultrasound after injecting air 0.01-0.1 ml into the external jugular vein of anaesthetized dogs (n = 7). At volumes of 0.05 ml and greater, there was a significant increase in both the maximum frequency of ...
Janssen M J - - 1993
We investigated the practical impact of the representation of the cardiac rhythm--the cardiotachogram--on two elementary spectral indexes in heart rate variability analysis: the low-frequency (0.07-0.14 Hz) and high-frequency (0.14-0.40 Hz) powers. Five commonly used tachograms (inter-beat interval function/series, counts, instantaneous heart rate function/series) were compared. Measurements were done on seven ...
Aisen M L - - 1993
Patients with severe action tremor have uncontrollable, relatively rapid oscillatory motion super-imposed on otherwise useable slower voluntary motor activity. Because a mechanical damper produces an opposing force proportional to velocity, applying damping loads to tremorous limbs should attenuate the (high-velocity) tremor component of movement while permitting the slower purposeful portion ...
Spiers J P - - 1993
Non-invasive techniques for assessing heart rate variability can be used either diagnostically, as in identification of autonomic neuropathy associated with diabetes mellitus or tissue rejection following cardiac transplantation, or as a prognostic indicator in coronary artery disease. The methodology is based upon calculation of successive R-R intervals from an electrocardiogram, ...
Hayano J - - 1993
Usefulness of complex demodulation (CDM) in assessing the frequency components of cardiovascular variability was assessed and, subsequently, this technique was utilized to determine the time-dependent responses of the low-frequency (LF) and high-frequency (HF) amplitudes of heart rate and blood pressure variabilities during postural tilt. CDM provides the time-dependent changes in ...
Leroyer P - - 1993
The purpose of this study was to analyse archery performance among eight archers of different abilities by means of displacement pull-hand measurements during the final push-pull phase of the shoot. The archers showed an irregular displacement negatively related to their technical level. Displacement signal analysis showed high power levels in ...
Hasenfuss G - - 1993
Isometric force, heat output, and aequorin light emission were measured in isolated muscle strips from nonfailing human hearts and from hearts with endstage failing dilated cardiomyopathy (37 degrees C; 30-180 beats per minute (bpm)). In nonfailing myocardium, peak twitch tension increased with higher rates of stimulation, whereas the force-frequency relation ...
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