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At least 505 records · Page 28Linked to original sources
PubMed1987

Evaluation of autonomic dysfunction in familial dysautonomia by power spectral analysis.

We examined the nature and extent of the autonomic control defect in patients with autonomic dysfunction using power spectral analysis of heart rate fluctuations. Heart rate variability and respiratory patterns were monitored and discrete blood pressure measurements were made during supine and standing positions in 10 ambulatory patients with familial dysautonomia and in controls. Postural hypotension without compensatory tachycardia was confirmed in the patients upon standing. The balance between sympathetic and parasympathetic activity was compared in both positions by quantifying the power of the low (0.04-0.095 Hz) and high (respiratory) frequency fluctuations in instantaneous heart rate. After changing from supine to standing position there was a small decrease in the low frequency power of heart rate fluctuations in the patients as opposed to a significant increase in controls. The mean power of fluctuations occurring at high frequency decreased only slightly in the patients compared to a marked decrease in the controls. We conclude that the fall in blood pressure, lack of appropriate heart rate modulation, and failure to increase low frequency heart rate power which occurred in the patients upon standing, are all due to lack of increased sympathetic output under the influence of gravity. The failure to decrease power in the respiratory frequency peak in the patients, suggests an abnormal retention of parasympathetic activity. This may be explained by parasympathetic compensation for the substantial sympathetic loss, or by a lack of appropriate inhibition of parasympathetic tone from baroreceptors or supraspinal structures.

Adult↗
PubMed2004

Adiponectin concentrations in sera from patients with type 2 diabetes are negatively associated with sympathovagal balance as evaluated by power spectral analysis of heart rate variation.

OBJECTIVE: To investigate whether cardiac autonomic activity, particularly sympathovagal balance as estimated by power spectral analysis (PSA) of heart rate variation (HRV), is associated with serum adiponectin concentrations in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: We studied 105 patients with type 2 diabetes (51 women and 54 men). Serum adiponectin concentrations were measured by sandwich enzyme-linked immunosorbent assay. HRV was determined automatically every 5 min over 24 h using Holter electrocardiographic recording. PSA of R-R intervals was performed using fast Fourier transformation. Low-frequency (both sympathetic and parasympathetic activities), high- frequency (pure parasympathetic activity), and the ratio of low-frequency-to-high-frequency power (LF-to-HF ratio), an index of sympathovagal balance, were used as indexes of cardiac autonomic activity. RESULTS: We found no significant correlation between serum adiponectin and low-frequency or high-frequency power in patients with diabetes. Serum adiponectin concentration correlated negatively with the 24-h LF-to-HF ratio (r = -0.343, P = 0.0009) and creatinine clearance (r = -0.411, P < 0.0001). Serum adiponectin concentrations were significantly higher in patients with overt albuminuria than in those with normoalbuminuria or microalbuminuria. In multivariate analysis controlling for sex, BMI, glycemic control, lipid profile, and renal function, serum adiponectin concentration showed an independent negative association with 24-h LF-to-HF ratio (beta = -0.332, P = 0.020). Furthermore, sex, HDL cholesterol, and renal function retained significant influence on the serum adiponectin concentration in patients with diabetes. CONCLUSIONS: Sympathovagal balance favoring relative sympathetic activation was associated with low serum concentrations of adiponectin in patients with type 2 diabetes.

Adiponectin↗
PubMed2004

[Experimental study on laser-induced plasma and its application to spectral analysis].

The article summarizes the progress in the experimental study on laser-induced plasma and its application to spectral analysis domestically and abroad in recent years. It emphatically elaborates the experimental research on the formation, radiation, electron temperature, electron density, and expansion velocity of laser-induced plasma under different conditions (gas composition and pressure, laser energy, laser wavelength, power density and observation height). In addition, in the respect of material composition analysis using the laser-induced plasma, the article mainly interprets two aspects: one is the way to collect directly the plasma emission so as to analyze solid, liquid and gaseous samples, the other is the spectrochemical analysis when laser ablation and ICP are used together. And the article also discusses the factors that influence the precision and the limit of detection.

Clinical Laboratory Techniques↗
PubMed1987

[Characteristics of the frequency component of EEG alpha rhythm of patients with neurosis-like schizophrenia (based on spectral analysis data)].

In 20 patients with neurosis-like schizophrenia and in 10 healthy subjects the authors, using the spectral analysis, assessed the composition of the alpha-range of the baseline EEG and studied the peculiarities of the frequency components of alpha-rhythm in various states. The patients were characterized by multimodality of the baseline EEG. The patients (versus the normal subjects) presented significantly different types of response of the main frequency components of EEG alpha-rhythm to the hyperventilation test.

Adolescent↗
PubMed1985

[Quantification of carotid atheroma, by vascular ultrasonics and spectral analysis, after myocardial infarction. Apropos of 80 cases].

A prospective study of carotid artery atheroma by vascular echotomography and spectral analysis was performed in 40 patients with myocardial infarction and 40 control subjects. Carotid artery atheroma was commoner in the group of patients with myocardial infarction (72.5% +/- 6.8%), earlier (9 years), more commonly bilateral (37.5% +/- 7.6%) and more stenotic (32.5% +/- 7.4%) than in the control group (p less than 0.000a, p less than 0.0001 and p less than 0.002, respectively). The severity of carotid artery atheroma correlated with the site of coronary artery disease; the following significant relationships were found: stenosing 40% and/or bilateral carotid atherosclerosis and left anterior descending disease (p less than 0.02); carotid atherosclerosis and double or triple vessel disease (p less than 0.05). The authors conclude that detection of carotid artery atheroma after myocardial infarction is valuable for two reasons: it gives an indication as to the severity of the coronary disease; carotid endarterectomy may be considered at the same time as coronary artery bypass surgery.

Arteriosclerosis↗
PubMed1974

Spectral analysis of electroencephalographic recordings of long duration by means of band-pass filters.

A method is proposed for spectral analysis of EEG recordings of long duration, using a set of band-pass filters. The sensitivity of the filters varies continuously over their full range, and the input signal is sampled at every sensitivity level. The full spectrum is presented as an array of numbers where the columns are the frequencies and the rows the sensitivity levels, printed as a percentage of the total possible responses of the filter (percent of activity). The logarithm of the numbers expressing the activity of a filter are used for the calculation of the regression line. Thus, the activity in each frequency is characterized by two parameters, the slope and the ordinate at origin, the slope being the more interesting one.

Computers↗
PubMed1994

Power spectral analysis of heart rate variability as a new method for assessing autonomic activity in the rat.

The authors studied power spectral analysis of heart rate variability in the rat, hypothesizing that the quantitative information provided by this analysis reflects the interaction between sympathetic and parasympathetic regulatory activities. For this purpose, an electrocardiogram was recorded from conscious and unrestrained Wistar rats (Nippon, Shizuoka) (12-16 weeks old) by a telemetry system and analyzed by a power spectrum. Because it was thought that the electrocardiogram recorded by the telemetry system could provide more reliable data to assess autonomic nervous activity than the tethering system, the telemetry recording system was used. There were two major spectral components in the power spectrum at low frequency (LF) (0.6 Hz) and high frequency (HF) (approximately 1.4 Hz). On the basis of these data, the authors defined two frequency bands of interest: LF (0.04-1.0 Hz) and HF (1.0-3.0 Hz). The power of LF was higher than that of HF in the normal rat. Atropine (2 mg/kg intraperitoneally) significantly reduced both HF and LF power. Propranolol (4 mg/kg intraperitoneally) also significantly reduced LF power; however, it had no significant effect on HF power. Thus, this study in the rat confirmed earlier observations in the conscious dog and human. Furthermore, the decrease in the parasympathetic mechanism produced by atropine was reflected by a slight increase in the LF/HF ratio. The LF/HF ratio appeared to follow the reductions of sympathetic activity produced by propranolol. From these results, the LF/HF ratio seemed to be a convenient index of parasympathetic and sympathetic interactions in the rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Power spectral analysis of EEG in a multiple-bedroom, multiple-polygraph sleep laboratory.

OBJECTIVES: We describe the methods for power spectral analysis (PSA) of sleep electroencephalogram (EEG) data at a large clinical and research sleep laboratory. The multiple-bedroom, multiple-polygraph design of the sleep laboratory poses unique challenges for the quantitative analysis of the data. This paper focuses on the steps taken to ensure that our PSA results are not biased by the particular bedroom or polygraph from which the data were acquired. METHODS: After describing the data acquisition system hardware, we present our signal amplitude calibration procedure and our methods for performing PSA. We validate the amplitude calibration procedure in several experiments using PSA to establish tolerances for data acquisition from multiple bedrooms and polygraphs. RESULTS: Since it is not possible to acquire identical digitized versions of an EEG signal using different sets of equipment, the best that can be achieved is data acquisition that is polygraph-independent within a known tolerance. We are able to demonstrate a tolerance in signal amplitude of +/- 0.25% when digitizing data from different bedrooms. When different data acquisition hardware is used, the power tolerance is approximately +/- 3% for frequencies from 1 to 35 Hz. The power tolerance is between +/- 3 and +/- 7% for frequencies below 1 Hz and frequencies between 35 and 50 Hz. Additional data demonstrate that variability due to the hardware system is small relative to the inherent variability of the sleep EEG. CONCLUSION: The PSA results obtained in one location can be replicated elsewhere (subject to known tolerances) only if the data acquisition system and PSA method are adequately specified.

Calibration↗
PubMed1995

Continuous, on-line, real-time spectral analysis of SAP signals during cardiopulmonary bypass.

We communicated the application of continuous, on-line, real-time power spectral analysis of systemic arterial pressure (SAP) signals during cardiopulmonary bypass when the heart was functionally but reversibly disconnected from the blood vessels. Based on observations from 15 cases of successfully completed coronary artery bypass grafting procedures, we found that the very low (0.00-0.08 Hz), low (0.08-0.15 Hz)-, high (0.15-0.25 Hz)-, and very high (0.80-1.60 Hz) frequency components of SAP signals exhibited differential changes before, during, and after cardiopulmonary bypass. In particular, the very low-frequency component, which purportedly represents the contribution of vasomotor activity to SAP, presented only a mild decrease in power during hypothermic cardioplegia. Interestingly, the total peripheral resistance also manifested only a slight reduction during the same period. On the other hand, the low-, high-, and very high frequency components were essentially eliminated. These results unveiled an active role for the blood vessels in the maintenance of SAP during cardiopulmonary bypass, possibly as a result of a maintained vasomotor tone as reflected by the sustained very low frequency component of the SAP signals.

Aged↗
PubMed1976

EEG spectral analysis in children with febrile convulsions.

The abnormal theta-rhythm of the EEG can be identified by use of spectral analysis. The rhythms appear as peaks in the power spectrum and can be considered as given, if the intensity of this peak is significantly higher than the average intensity and if a left-right coherence is present. Abnormal theta-rhythms in the parietal region are significantly more frequent in children with a histroy of febrile convulsions than in controls. This difference becomes especially obvious in the records with open eyes. According to previous investigations, the abnormal theta-rhythm is correlated with a genetically determined susceptibility to convulsions.

Child, Preschool↗
PubMed1977

[Correlation spectral analysis of the spontaneous impulse activity of cerebral cortex neurons].

Spontaneous unit activity in alert unrestrained rabbits was recorded simultaneously with two microelectrodes from the visual and sensorimotor cortex. The correlation analysis revealed that activity of majority of the neurons had no regular rhythm. But spectral analysis of the average correlograms showed existence of oscillations in the delta- and theta-ranges. The synergic type of interaction between cortical neurons was prevalent. Analysis of structure of the distant interaction showed the reduced probability of synergic spikes with periods 150-200 msec and less and the increased one with periods within 200-500 msec.

Animals↗
PubMed2002

Power spectral analysis of heart rate variability for assessment of diurnal variation of autonomic nervous activity in guinea pigs.

We established characteristics of power spectral analysis of heart rate variability, and assessed the diurnal variations of autonomic nervous function in guinea pigs. For this purpose, an electrocardiogram (ECG) was recorded for 24 hr from conscious and unrestrained guinea pigs using a telemetry system. There were two major spectral components, at low frequency (LF) and high frequency (HF) bands, in the power spectrum of HR variability. On the basis of these data, we defined two frequency bands of interest: LF (0.07-0.7 Hz) and HF (0.7-3.0 Hz). The power of LF was higher than that of HF in the normal guinea pigs. Atropine significantly reduced power at HF. Propranolol also significantly reduced power at LF. Furthermore, the decrease in the parasympathetic mechanism produced by atropine was reflected in a slight increase in the LF/HF ratio. The LF/HF ratio appeared to follow the reductions of sympathetic activity produced by propranolol. Autonomic blockade studies indicated that the HF component reflected parasympathetic activity and the LF/HF ratio seemed to be a convenient index of autonomic balance. Nocturnal patterns, in which the values of heart rate in the dark phase (20:00-06:00) were higher than those in the light phase (06:00-20:00), were observed. However, the HF, LF and the LF/HF ratio showed no daily pattern. These results suggest that the autonomic nervous function in guinea pigs has no clear circadian rhythmicity. Therefore, this information may be useful for future studies concerning the autonomic nervous function in this species.

Animals↗
PubMed1999

Enhancement of spectral analysis of myoelectric signals during static contractions using wavelet methods.

In this paper, we introduce wavelet packets as an alternative method for spectral analysis of surface myoelectric (ME) signals. Both computer synthesized and real ME signals are used to investigate the performance. Our simulation results show that wavelet packet estimate has slightly less mean square error (MSE) than Fourier method, and both methods perform similarly on the real data. Moreover, wavelet packets give us some advantages over the traditional methods such as multiresolution of frequency, as well as its potential use for effecting time-frequency decomposition of the nonstationary signals such as the ME signals during dynamic contractions. We also introduce wavelet shrinkage method for improving spectral estimates by significantly reducing the MSE's for both Fourier and wavelet packet methods.

Action Potentials↗
PubMedDate not supplied

Effect of contralateral internal carotid stenosis on the accuracy of continuous wave Doppler spectral analysis results.

In order to determine the effect of a hemodynamically significant contralateral stenosis on the results of a carotid Doppler study, 333 continuous wave Doppler spectral analysis studies were compared to angiography. For most grades of stenoses, both the peak frequency and the spectral broadening index were increased in the group of patients with contralateral carotid arterial stenoses greater than 50% by comparison with the group with less severe stenoses. Using receiver operating characteristic curves, the diagnostic accuracy was found to be slightly reduced by the presence of significant contralateral disease. Hence, when interpreting the results of carotid Doppler examinations, the presence or absence of a hemodynamically significant contralateral stenosis should be considered in determining the likelihood that an ipsilateral stenosis is present and in evaluating its severity.

Carotid Artery Diseases↗
PubMed1989

[Pilot study of the spectral analysis of the bifrontal EEG in healthy and newborn infants at risk].

The importance of neonatal bifrontal EEG recordings which were easily obtainable during intensive care was tested to improve the possibilities of computer-assisted analysis and to characterize cerebral cortical function of newborns-at-risk. The EEG was computerized by spectral analysis in 9 healthy term newborns and 6 term newborns-at-risk according to the age related patterns. Surprisingly, newborns-at-risk with good outcome show significant higher EEG spectral power than controls. But a secure monitoring is unpossible by bifrontal recordings alone. It was concluded that: 1. the bifrontal EEG recordings should be replaced by at least two interhemispheric recordings for neonatal cerebral monitoring, 2. the pattern-related analysis is necessary and 3. the discontinuous EEG is most suitable to characterize newborns-at-risk.

Brain Damage, Chronic↗
PubMed1989

Spectral analysis of the masseter and anterior temporalis: an assessment of reliability for use in the clinical situation.

The electromyogram (EMG) of contracting muscles can be analysed in the frequency domain by spectral analysis. However, there is a need to establish the reproducibility of spectral parameters such as mean power frequency (MPF). This study examined the variation of MPF (masseter and anterior temporalis) between and within recording sessions. The MPF was found to be significantly reliable for both muscles, but considerable within-subject variation was found despite comprehensive measures to standardize recording methods and conditions. It is concluded that MPF may have clinical application in the diagnosis and treatment of patients with facial pain arising from muscle dysfunctions, but caution should be exercised in interpreting small changes in frequency, given the inherent variability of MPF.

Adult↗
PubMed1979

Automated detection of EEG artifacts during sleep: preprocessing for all-night spectral analysis.

This paper describes a simple artifact detection algorithm which can be used when large amounts of EEG data are to be automatically processed via spectral analysis techniques in a general purpose digital computer, and visual inspection of each EEG epoch becomes an impossible task. The technique is based on a chi-square (chi(2)) goodness-of-fit test to a Gaussian distribution (CSQ), and it was applied to EEG epochs each 30 sec long. This test proved to be very sensitive to non-stationarities in the EEG amplitude distribution for a particular epoch, and it produced a large value for the chi(2) coefficient when an artifact was present. EEG epochs that gave rise to chi(2) coefficients of value larger than a heuristically determined minimum were discarded from further analysis. The above technique enabled efficient data reduction and reliable automatic off-line processing of 50 nights of sleep EEG via spectral techniques.

Action Potentials↗
PubMed1992

Spectral analysis of the rapid eye movement sleep electroencephalogram in right and left temporal regions: a biological marker of Alzheimer's disease.

Spectral analysis of electroencephalograms (EEGs) for both wakefulness and rapid eye movement (REM) sleep was performed over the temporal regions in 8 patients with mild to moderate Alzheimer's disease and in 8 age-matched control subjects. EEG slowing in Alzheimer patients was found to be much more prominent during REM sleep than during wakefulness. In addition, asymmetry on the awake EEG of Alzheimer patients was found to be even more prominent than on the REM sleep EEG. When EEG values of the most impaired hemisphere during REM sleep were examined, no overlap was found between the two groups either for the ratio of slow to fast frequencies or for percent power of each of the frequency bands. This was not the case for the awake EEG. These results suggest that diagnostically meaningful cutoff values for discriminating patients with mild to moderate Alzheimer's disease from age-matched control subjects can be derived from the REM sleep EEG of the temporal lobe.

Aged↗