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PubMedDate not supplied

Power spectral analysis of heart rate variability in healthy young women during the normal menstrual cycle.

This study investigated the fluctuations of autonomic nervous activities during the menstrual cycle. Twenty college females were tested for cardiovascular reactivity to mental challenge during both follicular and luteal phases across two menstrual cycles. Power spectral analysis of heart rate variability (HRV) was used to examine the autonomic nervous activities. At baseline, although heart rate and blood pressure did not differ across the menstrual cycle, the low-frequency (LF) component in the HRV was higher and the high-frequency (HF) component in the HRV was lower during the luteal phase than during the follicular phase. The LF/HF ratio was also significantly greater in the luteal phase. These data suggest that sympathetic nervous activities are predominant in the luteal phase as compared with follicular phase. In addition, the power spectral analysis of HRV has more sensitivity than heart rate or blood pressure in assessing the slight fluctuations of autonomic nervous activities during the menstrual cycle.

Adolescent↗

PubMed1976

[Multichannel EEG spectral analysis of the caffeine effect].

By means of multichannel Eeg spectral analysis the central effects of caffeine have been investigated during a controlled factorial study with 9 male volunteers. The effects of coffee and caffeine solution with equal concentration, decaffeinated coffee and hot water have been compared on the basis of analysis of variance. The factorial experimental design implemented a randomization concerning the sequence of substances as well as days of week. The principal findings are following: coffee and caffeine solution of equal concentration on the one hand cannot be readily distinguished concerning their Eeg effects, on the other hand the decaffeinated coffee and hot water exhibit very similar Eeg effects. Very marked differences, however, have been found between the two groups of substances. Coffee and caffeine solution both produce a remarkable, highly significant reduction of theta-amplitude, dominant theta-frequency and theta-frequency-variation. The alterations within the alpha range are mainly increase of dominant frequency and decrease of amplitude. These findings may be interpreted as signs of remarkable activation and elevation of vigilance. It should be pointed out that the Eeg effects of caffeine, as well as those of other compounds with central effects, are characterized by topographically different effects. These are not only quantitative, but partially qualitative differences.

Alpha Rhythm↗

PubMed1992

Power spectral analysis of the electrocardiogram in diabetic children.

In recent years it has been shown that alteration in heart rate variability can be used for the objective assessment of autonomic function in adult diabetic patients. Using a microcomputer based system for on-line monitoring and analysis of heart rate variability by power spectral analysis, 100 children with Type 1 (insulin-dependent) diabetes mellitus were studied. A highly significant negative correlation was identified between heart rate variability and duration of diabetes (r = -0.88, p less than 0.0001). The mean heart rate variability in patients with diabetes of duration 3 years or more was significantly lower in comparison to age-matched control subjects. A highly significant negative correlation was evident between heart rate variability and mean HbA1 in patients with duration of diabetes of 5 years or more. A mean HbA1 over 10% during this period was associated with the greatest reduction in heart rate variability. Serial measurements of heart rate variability in diabetic children may be of predictive value prior to the onset of symptomatic neuropathy.

Adolescent↗

PubMed1991

EEG spectral analysis and topographic mapping in Wilson's disease.

Computerized EEG spectral analysis and topographic mapping were performed on 14 patients with Wilson's disease (WD) and 10 normal subjects of comparable ages. The predominant EEG changes in WD were diffuse but uneven topographic abnormalities with a decrease in alpha activity, an increase in theta and delta activities, and a low voltage background mainly in the alpha frequency band. Eleven patients (80%) had at least one of the above EEG changes. Furthermore, topographic mapping provided more clearly defined foci of slowing and epileptiform activity. Patients with cerebral white matter involvement, akinetic-rigid syndrome, dystonia, or psychiatric symptoms tended to have more abnormal EEGs. It is concluded that EEG changes in WD are common and the quantitative EEG analysis can increase the likelihood of detecting mild or even subtle EEG abnormalities in individual patients as well as in the patient group.

Adolescent↗

PubMed1994

Sodium lactate increases sympathovagal ratios in normal control subjects: spectral analysis of heart rate, blood pressure, and respiration.

We used spectral analysis of heart rate (HR), blood pressure (BP), and respiration to examine the effects of lactate on cholinergic and adrenergic influences on HR and BP variability, a technique found to be very useful in cardiovascular research. We specifically used high frequency (0.2-0.5 Hz) and midfrequency (0.07-0.15 Hz) powers to study cholinergic and adrenergic activity in nine normal control subjects before and after lactate and placebo infusions. Our results demonstrate a marked decrease in cholinergic activity and a significant increase in sympathovagal ratios of HR modulation after lactate infusions. This altered sympathovagal balance may contribute to the panicogenic effects of lactate in panic disorder patients.

Adult↗

PubMed1997

Autonomic response to change of posture among normal and mild-hypertensive adults: investigation by time-dependent spectral analysis.

In this study, we applied the time-dependent spectral analysis approach (SDA) to investigate the autonomic changes occurring during a transition from supine to standing position (CP), in normal and unmedicated mild hypertensive subjects. The SDA method enables an accurate follow-up of the instantaneous changes in autonomic activity, even during the unsteady phase of the transition, where sudden changes in heart rate (HR) and arterial blood pressure (ABP) are observed. We were able to quantify the vagal withdrawal (reflected in the high frequency component of the time-dependent spectrum of HR fluctuations) in the immediate response to CP and the more slowly following sympathetic increase (reflected in the low frequency component of ABP). This general pattern was observed in both groups. In addition, our results identified an altered sympathetic response to CP in mild-hypertensives, as compared to normal adults. Their basal sympathetic activity is enhanced (higher mean HR and increased low frequency fluctuations in ABP) and their response to CP is reduced, as reflected only in the LF content of ABP fluctuations, relative to normals. No difference was observed in HR fluctuations, showing that there is no parasympathetically mediated alteration of the baroreflex control of HR in mild-hypertension.

Adult↗

PubMedDate not supplied

[The use of spectral analysis in studying the E.E.G. under enflurane (author's transl)].

Spectral study of E.E.G. activity under enflurane anaesthesia shows a mild and early increase in global power distributed over the whole spectrum up to 20 c/sec, initially without dominant activity. Slow activity at 4-6 c/sec occurs later and gradually becomes slower, although without providing what could be called a specific pattern. These results have been compared with the same spectral analysis approach in anoxia in the normal subject and in epileptic subjects. Our experience so far does not allow the identification of the discharges observed the enflurane as epileptic discharge.

Adolescent↗

PubMed1978

[Alpha activity in a group of schizophrenics: spectral analysis and comparison with a control group (author's transl)].

Spectral analysis of tracings from four leads; C3-P3, P3-O1, C4-P4, and P4-O2, were used to compare the results of fiftyseven electroencephalograms from 10 schizophrenics, and 14 normal subjects used as controls. The results show that the mean frequencies of the alpha waves are identical in schizophrenics and controls. Patients with hebephrenia show the lowest variations in alpha wave frequency but with the highest voltage, whereas paranoid schizophrenics have tracings with the lowest amplitude and the greatest variation in frequency. There is also better left intrahemispheric correlation of relative alpha intensities in those patients with the lowest variation in right alpha intensity in relation to controls. The preliminary results suggest that there is a reduction in functional asymmetry of the hemispheres in the electroencephalograms from schizophrenics, when looking at the alpha activity.

Adult↗

PubMed1998

Spectral analysis of heart rate, arterial pressure, and muscle sympathetic nerve activity in normal humans.

We investigated the frequency components of fluctuations in heart rate, arterial pressure, respiration, and muscle sympathetic nerve activity (MSNA) in 11 healthy women using an autoregressive model and examined the relation among variables using Akaike's relative power contribution analysis with multivariate autoregressive model fitting. Power spectral analysis of MSNA revealed two peaks, with low-frequency (LF) and high-frequency (HF) components. The LF component of MSNA was a major determinant of the LF component of arterial pressure and R-R interval variability (0.70 +/- 0.07 and 0.18 +/- 0.05, respectively). The effect of the LF component of MSNA on arterial pressure showed no change in response to propranolol but was diminished (0.35 +/- 0.08) by phentolamine (P < 0.02). The effect of the LF component of MSNA on R-R interval was not altered by pharmacological sympathetic nerve blockade. The HF component of MSNA did not influence other variables but was influenced by R-R interval, arterial pressure, and respiration. These findings indicate that the LF component of MSNA reflects autonomic oscillations, whereas the HF component is passive and influenced by other cardiovascular variables.

Adolescent↗

PubMed1986

Atropine unmasks bed-rest effect: a spectral analysis of cardiac interbeat intervals.

Bed-rest deconditioning is suspected to reduce cardiac reserve, possibly by impairing autonomic function. Heart rate response in normal subjects reveals considerable variability, reflected by a relatively broadband interbeat interval power spectrum. A reduction in this autonomically modulated variability would be predicted to cause a narrowing of the spectrum. We retrospectively analyzed data from 10 aerobically conditioned men (age range 35-49 yr) who had undergone orthostatic tolerance testing with lower body negative pressure pre-bed rest and after 7-10 days of bed rest, while on placebo and after intravenous atropine. Spectra were derived by Fourier analysis of 128 interbeat interval data sets. Spectral power was estimated by computing the root-mean-square (rms) values (mean +/- SD) for the band encompassing the 2nd to 64th harmonics from subjects with a sufficient number of beats: placebo rms is 93 +/- 33 ms for pre-bed rest and 84 +/- 38 ms for bed rest (NS, n = 6); atropine rms is 63 +/- 24 ms for pre-bed rest and 40 +/- 23 ms for bed rest (P less than 0.01; n = 7). These data suggest that atropine "unmasks" a deconditioning effect of bed rest in athletic men, evidenced by a reduction in interbeat interval spectral power not apparent with placebo. Spectral analysis offers a useful means of quantitating the effects of bed-rest deconditioning and autonomic perturbations on cardiac dynamics.

Adult↗

PubMed2003

[Spectral analysis of systolic blood pressure in atrial fibrillation].

OBJECTIVES: Power spectral analysis was used to analyze fluctuations of systolic blood pressure and heart rate. METHODS: Non-invasive finger plethysmography and electrocardiography were performed in 20 patients with chronic atrial fibrillation and in 10 age-matched healthy subjects with normal sinus rhythm. The impulse train was stored on a personal computer and the power spectrum of R-R interval and systolic blood pressure were obtained by Fourier analysis (0.01-0.03 Hz). The power spectrum (log power vs log frequency) characteristically revealed a linear regression as 1/f beta. RESULTS: The R-R interval spectrum during atrial fibrillation showed a white noise-like flat spectrum when plotted as log power against log frequency, whereas the systolic blood pressure spectrum during atrial fibrillation showed a 1/f noise-like negative slope linear pattern. The spectrum exponent of systolic blood pressure in patients with atrial fibrillation was significantly lower than that in subjects with normal sinus rhythm (2.3 +/- 0.1 vs 1.3 +/- 0.1, p < 0.0001). CONCLUSIONS: Systolic blood pressure fluctuation in patients with atrial fibrillation has a fractal component and is more complex than that of healthy subjects with normal sinus rhythm.

Atrial Fibrillation↗

PubMedDate not supplied

[Assessment of anesthesia adequacy with spectral analysis of the heart sinus rhythm].

The information density of spectral analysis of the variability of sinus rhythm to be used in diagnosing the neurovegetative activity in operation trauma was studied in 32 patients in the course of anesthesia and operation. It is suggested on the basis of the found the method can in monitoring the anesthesia adequacy.

Anesthesia↗

PubMed1991

[Energy index of heart rate spectral analysis for the assessment of autonomic nerve activities].

Heart rate spectral analysis was performed in 17 male healthy volunteers by changing their positions (supine or standing) and respiratory rates (8, 10, 12, 15 and 20 bpm). Furthermore, analysis was made by a multiple regression method on parameters such as R-R interval, tidal volume, respiratory time and positions of the subjects which may contribute to the peak power values of high frequency components (HFC, synchronous with respiratory patterns and of low frequency components (LFC, about 0.1Hz). HFC power was found to be significantly dependent on R-R interval and respiratory time, but not on tidal volume or position. Following equation was obtained. HFCP = 11.3 X RTX (RR-0.246) HFCP: HFC power value (msec) RT: respiratory time (sec) RR: R-R interval (sec) Therefore, HFCP or area under the curve (AUC) of HFC is not appropriate for the assessment of autonomic nerve activities, especially when respiratory rate or heart rate is changing. The intensity of physical wave is in proportion to (amplitude X frequency). Consequently, in a case where frequency is changeable, (amplitude X frequency) is a good index of the oscillatory energy. Therefore, sigma (power X frequency) is proposed as a suitable index for a certain component of power-spectrum. Parasympathetic activity should be assessed by the following index induced from the previously mentioned equation. RR adjusted HFEI (high frequency energy index) = sigma (power X frequency)/(RR-0.246) (0.15Hz less than frequency less than 0.4Hz). Similarly, low frequency components which reflect the sympathetic activity should be assessed by the following equation. LFEI (low frequency energy index) = sigma (power X frequency) (0.05Hz less than frequency less than 0.15Hz). The assessment of autonomic nerve activities becomes more appropriate by using these indices especially when heart rate and respiratory rate are changing.

Adult↗

PubMed1989

[Spectral analysis of the heart rhythm of elderly patients with hypertension].

Spectral analysis of the cardiac rhythm was employed to investigate the vegetative regulation of the cardiac function in patients of elderly age suffering of hypertensive disease without and association with chronic circulatory insufficiency. The necessity is substantiated of differential use of hypotensive agents depending on the individual peculiar aspects of vegetative regulation of the cardiac activity.

Adult↗

PubMed2001

On multivariate spectral analysis of fMRI time series.

Most of functional magnetic resonance imaging (fMRI) time series analysis is based on single voxel data evaluation using parametric statistical tests. The result of such an analysis is a statistical parametric map. Voxels with a high significance value in the parametric test are interpreted as activation regions stimulated by the experimental task. However, for the investigation of functional connectivities it would be interesting to get some detailed information about the temporal dynamics of the blood oxygen level-dependent (BOLD) signal. For investigating that behavior, a method for fMRI data analysis has been developed that is based on Wiener theory of spectral analysis for multivariate time series. Spectral parameters such as coherence measure and phase lead can be estimated. The resulting maps give detailed information on brain regions that belong to a network structure and also show the temporal behavior of the BOLD response function. This paper describes the method and presents a visual fMRI experiment as an example to demonstrate the results.

Adult↗

PubMed1995

[Arrhythmias, autonomic function and spectral analysis of heart rate variation in patients with stable chronic pulmonary disease].

Autonomic function, the frequencies of arrhythmias, and outcome were studied in patients with stable chronic pulmonary disease (n = 67. Old tuberculosis, n = 35. Chronic pulmonary emphysema, n = 32) and in age-matched healthy elderly. The frequencies of arrhythmias were computed and spectral analysis was done with data obtained from 24-hour Holter ECG monitoring. The minimum heart rates of the patients were high. The minimum heart rate fell at night in the controls, but not in the patients. The patients had more PVCs than the controls, however sudden death due to arrhythmias did not occur. The LF/HF ratios obtained by spectral analysis of heart rate were lower in the patients than in the controls. There were no significant differences in age, respiratory rate, arterial blood gases, pulmonary-function tests, arrhythmias, or in the hourly distribution of the minimum heart rate between patients who died within 3 years and those who lived for more than 5 years. However, the LF/HF ratio in those who died was significantly lower than in the other groups. These results suggest that functional disturbance of the autonomic nervous system is related to outcome in patients with stable chronic pulmonary disease.

Aged↗

PubMed2004

Spectral analysis of internal carotid arterial Doppler signals using FFT, AR, MA, and ARMA methods.

In this study, Doppler signals recorded from internal carotid artery of 45 subjects were processed by PC-computer using classical (fast Fourier transform) and model-based (autoregressive, moving average, autoregressive moving average (ARMA) methods) methods. Power spectral density estimates of internal carotid arterial Doppler signals were obtained using these spectral analysis methods. The variations in the shape of the Doppler power spectra as a function of time were presented in the form of sonograms in order to determine the degree of internal carotid artery stenosis. These Doppler power spectra and sonograms were then used to compare the applied methods in terms of their frequency resolution and the impact on determining stenosis in internal carotid arteries. Based on the results, performance characteristics of the autoregressive and ARMA methods were found extremely valuable for spectral analysis of internal carotid arterial Doppler signals obtained from healthy subjects and unhealthy subjects having artery stenosis.

Adolescent↗

PubMed1981

[Histopathologic representation of a tumoral EEG focus by spectral analysis].

This work is intended for those: (1) wishing to use spectral analysis for clinical purposes and who have ony limited computer facility possibilities at their disposal; (2) who are looking for a simple and, above all, easily and immediately interpretable graphic representation of the spectral data developed by a cerebral focal lesion, which can be interpreted even by an inexperienced clinician. Finally this paper emphasized the value of a particularly interesting clinical sign from quantitative analysis, namely the EEG supervision of cerebral tumours, either evolving or recovering.

Astrocytoma↗