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PubMed1988

[Pacemakers of the upper urinary tract using power spectral analysis of spontaneous activity].

Spontaneous activity of isolated smooth muscle strips of the upper urinary tract has been analysed by time series analysis. Frequency components of spontaneous contractions of the human urinary tract have been determined quantitatively by means of power spectral analysis. This method allows to characterise exact frequency components of rhythmicity in various parts of the urinary tract and accordingly helps to localise the site of various pacemakers. The results indicate tentatively the existence of two different pacemakers located in the wall of calix and pelvis. Furthermore, it is assumed that these pacemakers complement each other both cooperatively and by additive functioning, as though in shifts (reverberation), to stimulate urine transport through the pyeloureter.

Animals↗
PubMed1994

Ambulatory recording and power spectral analysis by autoregressive modelling of polygraphic sleep signals in patients suffering from chronic pain.

A portable digital recording system and the Nightingale sleep analyser have been applied to record polygraphical sleep signals in patients suffering from chronic pain. Using ambulatory recording the patient can sleep at home making the sleep more natural and reducing the costs. The recording system gives digital recordings of very good quality. It is shown that the Nightingale sleep analyser performs automatic sleep analysis with a quality comparable to visual interrater performance on disordered sleep. It furthermore provides means for extraction of spectral information useful for the description of the sleep-wakefulness processes and for diagnosing the sleep disorders. Using AR-model-based power spectral analysis, it is also shown that the power content in the alpha band relative to the delta power is significantly higher in patients suffering from non-specific chronic pain as compared to normal persons.

Chronic Disease↗
PubMed1981

Power spectral analysis of EEG drug response in the kindled rat brain.

The specificity of procaine as a limbic epileptic focus activator was investigated in rats kindled in the amygdala. Power spectral analysis of spontaneous EEG was employed to assess the effects of two doses of procaine HCl (60 and 100 mg/kg) on the kindled and unkindled amygdala. Analysis revealed a dose-dependent increase in power in the 1--15 c/sec frequency band of the EEG. Power increases were greater in the kindled than in the unkindled amygdala of the same rat, and exceeded power changes induced in unkindled controls. The effects of procaine on the EEG persisted past the day of injection, but returned to baseline by the fifth day. Changes in power over days following an injection of procaine differed in the kindled and unkindled amygdala amygdala of the same rat. The kindled amygdala showed an increase on the day of injection, followed by a steady decline to baseline. The unkindled amygdala showed a delayed rise in power on day 2 and then a decline to baseline levels over days. Comparison of spectral changes induced by drug and by electrically triggered seizures suggested that procaine induces EEG patterns which are seizure-like in the absence of seizures. The data are consistent with the view that procaine may be a useful focus specific activator in the detection of limbic epilepsy.

Amygdala↗
PubMed1998

Power spectral analysis of heart rate variation in diabetic patients with neuropathic foot ulceration.

OBJECTIVE: To evaluate the relationship between diabetic autonomic neuropathy and diabetic neuropathic foot ulceration, we used power spectral analysis (PSA) of heart rate variation, which provides the accurate simultaneous quantification of parasympathetic and sympathetic activities, to assess autonomic function in diabetic patients. RESEARCH DESIGN AND METHODS: We studied 55 NIDDM patients including 10 diabetic patients without neuropathy, 23 diabetic patients with neuropathy and no history of foot ulceration, and 22 diabetic patients with neuropathic foot ulceration. We performed PSA of 100 R-R intervals at rest and analyzed the results by fast Fourier transformation. RESULTS: The low frequency (LF) power, which reflects sympathetic activity, and the high frequency (HF) power, which reflects parasympathetic (vagal) activity, were inversely correlated with the duration of diabetes and the fasting plasma glucose (FPG) levels. By multiple regression analysis, the FPG remained with significant influence on both LF and HF powers. The LF and HF powers were positively correlated with motor nerve conduction velocity (MCV) and sensory nerve conduction velocity (SCV) in the upper and lower limbs and the coefficient of variation of R-R intervals. The LF and HF powers were significantly reduced in patients with neuropathy and patients with foot ulceration compared with patients without neuropathy. Although the median MCV and SCV were similar between diabetic patients with neuropathy and patients with foot ulceration, both the LF and HF powers were significantly decreased in patients with foot ulceration compared with patients with neuropathy. There was no difference in the value of the LF:HF ratio, an index of sympathovagal balance, among three subgroups. We observed a positive correlation between LF and HF power in all subjects; however, the LF and HF powers were not correlated in the subgroups of patients with foot ulceration. CONCLUSIONS: These results showed that diabetic patients with neuropathic foot ulceration have a greater impairment in spectral indexes of autonomic activity obtained by PSA than patients with neuropathy and no history of foot ulceration, whereas no difference was present in nerve conduction velocities.

Age Factors↗
PubMed1998

Multiple-echo proton spectroscopic imaging using time domain parametric spectral analysis.

A multiple-echo MR spectroscopic imaging (MRSI) method is presented that enables improved metabolite imaging in the presence of local field inhomogeneities and measurement of transverse relaxation parameters. Short echo spacing is used to maximize signal energy from inhomogeneously line-broadened resonances, and time domain parametric spectral analysis of the entire echo train is used to obtain sufficient spectral resolution from the shortened sampling periods. Optimal sequence parameters for 1H MRSI are determined by computer simulation, and performance is compared with conventional single-echo acquisition using phantom studies at a field strength of 4.7 T. A preliminary example for use at 1.5 T is also presented using phantom and human brain MRSI studies. This technique is shown to offer improved performance relative to single-echo MRSI for imaging of metabolites with shortened T2* values due to the presence of local field inhomogeneities. Additional advantages are the intrinsic measurement of metabolite T2 values and determination of metabolite integrals without T2 weighting, thereby facilitating quantitative metabolite imaging.

Aspartic Acid↗
PubMed1990

EEG correlates of hypnotic susceptibility and hypnotic trance: spectral analysis and coherence.

EEG was recorded monopolarly at frontal (F3, F4), central (C3, C4) and occipital (O1, O2) derivations during A-B-A conditions of waking rest, hypnosis (rest, arm immobilization, mosquito hallucination, hypnotic dream), and waking rest. Stringently screened on several measures of hypnotic susceptibility, 12 very low hypnotizable and 12 very highly hypnotizable, right-handed undergraduate, subjects participated in one session. Evaluations were Fast-Fourier spectral analysis, EEG coherence between selected derivations and maximum spectral power within EEG bands. In eyes open and closed conditions in waking and hypnosis, highly hypnotizable subjects generated substantially more mean theta power than did low hypnotizable subjects at all occipital, central and frontal locations in almost all conditions of waking and hypnosis, with a larger difference in frontal locations. Both low and high hypnotizables showed increased mean theta power in hypnosis, suggesting an intensification of attentional processes and imagery enhancement. Mean alpha power was never a predictor of hypnotic susceptibility. Interactions with hypnotic susceptibility showed that highly susceptible subjects had more beta activity in the left than right hemispheres, while low susceptible subjects showed only weak asymmetry. No main effects for or interactions between waking/hypnosis and hypnotic level were found for coherence between derivations or maximum spectral power within theta, alpha and beta EEG bands.

Alpha Rhythm↗
PubMed2002

Effects of nicardipine and diltiazem on fractal features of short-term heart rate variability--application of coarse graining spectral analysis.

PURPOSE: This study was designed to investigate the effects of nicardipine and diltiazem on the fractal features of short-term heart rate variability (HRV), using coarse graining spectral analysis (CGSA). METHODS: Eighteen healthy volunteers participated in this study; they were divided into two groups according to the drug administered. Five-minute electrocardiogram and arterial pressure recordings were made during stepwise infusions of either nicardipine (0.4, 0.8, 1.6, and 3.2 microg.kg(-1).min(-1)) or diltiazem (2, 4, 8, and 16 microg.kg(-1).min(-1)) under rate-controlled breathing at 0.25 Hz. CGSA broke down the total power of the time series into harmonic (low frequency [0.0-0.15 Hz; LF] and high frequency [0.15-0.5 Hz; HF]) and nonharmonic (fractal) components. Cardiac sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) activity indicators were evaluated as the ratios LF/HF and HF/TP (total spectral power), respectively. Fractal components were evaluated as %fractal and the spectral exponent beta of 1/f(beta). RESULTS: Compared with control measurements, the maximum dose of nicardipine infusion caused a significant decrease in systolic arterial pressure, a significant increase in the mean heart rate, and a significant increase in plasma norepinephrine level, findings that were associated with significant increases in %fractal and beta values (54.2 +/- 13.3 vs 75.6 +/- 9.8, and 0.86 +/- 0.22 vs 1.32 +/- 0.46, respectively; P < 0.05). PNS and SNS indicators showed decreased and increased values, respectively. Diltiazem caused a reduction in arterial pressure; however, no other parameters, including the nonharmonic components of HRV, were affected by this drug. CONCLUSIONS: These findings strongly suggest that nicardipine suppresses vagal cardiac neural outflow and activate the SNS, an action which, subsequently, causes changes in the fractal features of HRV. Although diltiazem reduces arterial pressure, it preserves the basic neural balance of the autonomic nervous system in regard to heart rate control.

Journal Article↗
PubMed1981

Power spectral analysis of the flash-evoked after-discharge.

A quantitative measure of the flash-evoked after-discharge (FEAD) in the rat was derived using power spectral analysis. The utility of this method of measurement was demonstrated by quantifying the suppression of FEAD by the drug yohimbine. This method of quantification would facilitate the use of FEAD for the purpose of screening antiepileptic drugs.

Animals↗
PubMed1988

Spectral analysis of muscular sound at low and high contraction level.

The activated muscle generates a low frequency rumbling noise, which is known as the Sound-MyoGram (SMG). Spectral analysis of the SMG is carried out in this work, in order to: (i) check the adequacy of both the Fast Fourier Transform (FFT) and the Maximum Entropy Spectrum Estimation (MESE). Because it is a well known technique, the FFT method is only briefly described, while the philosophy of the MESE method is given in more detail and completed with a description of the recursive algorithm; (ii) select a frequency parameter suitable to describe the SMG. For this purpose two well-defined physiological conditions (20% and 80% Maximal Voluntary Contraction) have been adopted in order to provide a safe reference for the interpretation of the findings. The results show that: (a) both FFT and MESE are adequate to estimate the SMG Power Spectrum; (b) both the mean and the median frequency are suitable parameters, the mean frequency being the more favourable one; (c) the SMG Power Spectrum is a promising tool to study the muscle activation modalities.

Adult↗
PubMed2004

Estimating cardiac autonomic activity during sleep: impedance cardiography, spectral analysis, and Poincaré plots.

OBJECTIVE: To compare noninvasive measures of cardiac autonomic activity during sleep. METHODS: The absolute and normalized (n.u.) high and low frequency peaks from the spectral analysis of R-R intervals (HF, LF, HFn.u., LFn.u.), LF/HF ratio, pre-ejection period (PEP) from impedance cardiography, and the autocorrelation coefficient (rRR) as illustrated in Poincaré plots were measured during night-time sleep in 9 young healthy subjects. Heart rate and blood pressure were also recorded. RESULTS: Heart rate was significantly associated with cardiac sympathetic activity (PEP, average r=-0.46), but not with cardiac parasympathetic activity (HF, average r=-0.17). rRR was significantly associated with heart rate (average r=0.41), and LF/HF (average r=0.69), but not with PEP or HF. From NREM to REM sleep, heart rate, LFn.u., LF and rRR significantly increased, HFn.u. significantly decreased, LF/HF showed an increasing trend (P=0.07) and PEP showed a decreasing trend (P=0.06). Blood pressure and HF were highly variable without significant changes from NREM to REM sleep. CONCLUSIONS: Cardiac parasympathetic activity (HF) does not vary greatly between sleep stages. Cardiac sympathetic activity (PEP) decreases linearly during sleep. rRR and LF/HF can track sympathovagal changes during sleep, but cannot differentiate between changes in cardiac parasympathetic and sympathetic activity. The relative advantages and disadvantages of the different measures are discussed.

Adult↗
PubMed1988

Spectral analysis of the EEG in craniocerebral trauma.

The objectives of the present study were to evaluate the relationship between the fractional amplitudes of the EEG derived from power spectral analysis (PSA) of the electroencephalogram (EEG) and depth of coma measured clinically with the Glasgow Coma Score, and to assess the accuracy of PSA in predicting long-term outcome. Thirty-two patients rendered unconscious by blunt head injury (mean (GCS = 7) had intermittent EEG recordings daily from 1-10 days post injury. There was a significant correlation between fractional amplitude of the EEG and the GCS. The rate and magnitude of change in the EEG and GCS were also correlated. There were significant differences in PSA parameters between improved and deteriorated patient groups at the termination of monitoring (p = .02) and in the change of PSA parameters over time (p = .02). Using linear discriminant analysis of PSA parameters, the accuracy of outcome prognostication based on the six month outcome was approximately 75%. Accurate classification of outcome was possible in a number of patients in whom there was little or no change in the GCS during the period of monitoring.

Adolescent↗
PubMed2006

Effects of prolonged surface pressure on the skin blood flowmotions in anaesthetized rats--an assessment by spectral analysis of laser Doppler flowmetry signals.

The objective of this study is to assess the effect of prolonged surface compression on the skin blood flowmotion in rats using spectral analysis based on wavelets transform of the periodic oscillations of the cutaneous laser Doppler flowmetry (LDF) signal. An external pressure of 13.3 kPa (100 mmHg) was applied to the trochanter area and the distal lateral tibia of Sprague-Dawley rats via two specifically designed pneumatic indentors. The loading duration was 6 hours/day for 4 consecutive days. Five frequency intervals were identified (0.01-0.04 Hz, 0.04-0.15 Hz, 0.15-0.4 Hz, 0.4-2 Hz and 2-5 Hz) corresponding to endothelial related metabolic, neurogenic, myogenic, respiratory and cardiac origins. The absolute amplitude of oscillations of each particular frequency interval and the normalized amplitude were calculated for quantitative assessments. The results showed that (1) tissue compression following the above schedule induced significant decrease in the normalized amplitude in the frequency interval of 0.01-0.04 Hz both in the trochanter area (p < 0.001) and tibialis area (p = 0.023), (2) prolonged compression induced significant increase in the absolute amplitude (p = 0.004 for the trochanter area and p = 0.017 for the tibialis area) but significant decrease in the normalized amplitude (p = 0.023 for the trochanter area and p = 0.026 for the tibialis area) in the frequency interval of 0.15-0.4 Hz, and (3) at the tibialis area, the flowmotion amplitude (frequency interval 0.15-0.4 Hz) measured prior to the daily tissue compression schedule was found to be significantly higher on day 4 than the measurements obtained on day 1. However, this finding was not observed at the trochanter area. Our results suggested that prolonged compression might induce endothelial damage and affect the endothelial related metabolic activities.

Adaptation, Physiological↗
PubMedDate not supplied

Sympathetic regulation in rabbits with heart failure: experience using power spectral analysis of heart rate variability.

1. In five intact rabbits beta-adrenoreceptor blockade (i.v. propranolol), and combined cardiac blockade (i.v. propranolol plus i.v. methscopolamine sulphate) revealed that spectral power of heart rate (HR) variability at low frequencies (LF:0.0625-0.1875 Hz) was modulated predominantly by the sympathetic nervous system and power at high frequencies (HF:0.4373-0.5625 Hz) by vagal influences. 2. In 16 rabbits resting power of HR at LF and changes in LF power in response to maximal treadmill exercise were examined prior to and after 4 and 6 weeks of doxorubicin treatment (1 mg/kg twice weekly). 3. The development of doxorubicin-induced congestive heart failure (CHF) was accompanied by a progressive increase in resting LF power [control, 8.5 +/- 2.1; 4 weeks, 13.4 +/- 1.8; 6 weeks, 21.9 +/- 3.5 (beats/min)2, P < 0.005]. 4. Power spectral analysis (PSA) of HR variability in the immediate post-exercise period showed no change from resting values in normal rabbits [5.3 +/- 1.4 vs 8.5 +/- 2.1 (beats/min)2, P > 0.05] whereas CHF rabbits showed falls in LF power after 4 weeks [4.6 +/- 1.0 vs 13.4 +/- 1.8 (beats/min)2, P < 0.005] and 6 weeks [6.5 +/- 2.4 vs 21.9 +/- 3.5 (beats/min)2, P < 0.005] of doxorubicin treatment. 5. It was concluded that PSA of HR variability reflects the autonomic regulation of sinus node function in conscious rabbits. In doxorubicin-treated animals, the rise in LF power reflects increased sympathetic activity as CHF develops. However, the apparent paradoxical fall in LF power with exercise in these animals underscores the need for caution in interpretation of PSA profiles.

Adrenergic beta-Antagonists↗
PubMed1996

Spectral analysis of hemodynamics during left ventricular assistance.

In order to analyze the autonomic nervous system during left ventricular (LV) assistance, fluctuations in hemodynamic derivatives were evaluated by a spectral analyzing method using a fast fourier transform (FFT) methodology. After the left pleural cavity was opened through the fourth intercostal space under general anesthesia, a pneumatically driven ventricular assist system was implanted as in left heart bypasses in chronic animal experiments, using three healthy adult goats. Hemodynamic parameters with and without LV assistance were recorded on a magnetic tape in the awake condition then analyzed in a computer system through an A-D convertor. Power spectral analysis was performed on a beat-to-beat basis for the evaluation of the fluctuations. During copulsation mode LV assistance, Mayer wave fluctuations (0.1 Hz) were significantly increased compared with counterpulsation mode LV assist, suggesting an increase in sympathetic tone. Co-pulsation mode LV assist is reported to increase the afterload of the natural left ventricle, thus, the sympathetic tone may be increased to maintain a natural heart output.

Analysis of Variance↗
PubMed2004

Fourier transform infrared spectral analysis of degenerative cartilage: an infrared fiber optic probe and imaging study.

A preliminary investigation into the diagnostic potential of an infrared fiber optic probe (IFOP) for evaluating degenerative human articular cartilage is described. Twelve arthritic human tibial plateaus obtained during arthroplasty were analyzed using the IFOP. Infrared spectra were obtained from IFOP contact with articular surface sites visually graded normal or degraded (Collins Scale grade 1 and grade 3, respectively). Comparisons of infrared spectral parameters (peak heights and areas) were made to elucidate spectral indicators of surface degeneration. IFOP spectral analysis revealed subtle but consistent changes between grades 1 and 3 sites. Infrared absorbance bands arising from type II collagen were observed to change with degradation. More degraded tissues exhibited increased amide II (1590-1480 cm(-1))/1338 cm(-1) area ratio (p=0.034) and decreased 1238/1227 cm(-1) peak ratio (p = 0.017); similar changes were seen with Fourier transform infrared imaging spectroscopy (FT-IRIS) analysis. Grades 1 and 3 cartilage showed consistent spectral differences in the amide II, III, and 1338 cm(-1) regions that are likely related to type II collagen degradation that accompanies cartilage degeneration. These results suggest that it may be possible to monitor subtle changes related to early cartilage degeneration, allowing for IFOP use during arthroscopy for in situ determination of cartilage integrity.

Aged↗
PubMed2006

Long-term follow-up of changes in fibrillation waves in patients with persistent atrial fibrillation: spectral analysis of surface ECG.

BACKGROUND: Little is known about the shortening of atrial refractoriness as a result of electrical remodeling in atrial fibrillation (AF) in clinical cases, especially in terms of long-term follow-up, because of a lack of noninvasive testing methods. METHODS AND RESULTS: The present study population comprised 38 consecutive patients with persistent AF (PAF, >1 month). Before and after the follow-up period of 1-14 months, surface ECGs were recorded for analysis. In each case, the fibrillation wave was purified by subtracting the QRS-T complex template and then power spectral analysis was performed. The mean fibrillation cycle length (FCL) and FCL coefficient of variation (FCL-CV) were determined from peak power frequency in 20 epochs in each recording. The change in FCL (FCL) was calculated by subtracting the baseline FCL from the FCL after the follow-up period. To correct for the difference in the follow-up period, DeltaFCL was divided by the follow-up period in each case. In 38 cases, mean FCL decreased from 160+/-20 ms to 151+/-19 ms (p<0.05), and the FCL-CV also decreased from 15+/-9% to 12+/-5% (p<0.05). The corrected DeltaFCL was -2.4+/-7.6 (ms/month) and there was a significant negative correlation between corrected DeltaFCL and baseline FCL (p<0.01). CONCLUSION: Shortening of the FCL during a relatively long-term follow-up period was observed in patients with PAF.

Atrial Fibrillation↗
PubMed1977

Lateralisation of speech dominance by spectral analysis of evoked potentials.

A computerised evoked potential test for the lateralisation of speech dominance was compared with the intracarotid sodium amylobarbitone test in 22 epileptic patients. Based on spectral analysis, the computer test correctly predicted the speech dominance of 15 of 16 left speech dominant and five of six right speech dominant patients. This non-invasive test is simple, quick, and innocuous and can be easily implemented on a small laboratory computer.

Adolescent↗
PubMed1979

Spectral analysis of human inspiratory diaphragmatic electromyograms.

The inspiratory diaphragmatic EMG was recorded via esophageal electrodes in six normal subjects. The EMG and ECG signals were analyzed by power density spectral analysis, before and after band-pass filtering (20--1,600 Hz). The EMG spectrum was concentrated in the bandwidth 25--250 Hz. Electrode motion introduced a significant artifact only at low frequencies. The ECG spectrum was also concentrated at lower frequencies, but substantial power from the cardiac signal spilled over across most of the EMG spectrum. Band-pass filtering was therefore effective in minimizing the former but not the latter. Of the various power and frequency parameters used to quantitate the EMG spectrum, the most stable was the centroid frequency. This was reproducible within and between subjects, and was not affected by changing tidal volume or inspiratory flow rate.

Adult↗