Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spectral Analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed1993

[Autonomic nervous function of vertiginous patients--assessment by spectral analysis of heart rate variability].

Autonomic nervous function in 68 vertiginous patients and 33 controls was studied using power spectral analysis of heart rate variability. First, a system was developed which computes the power spectral density (PSD) of beat-to-beat heart intervals using a continuous non-invasive finger blood pressure recording obtained with the FINAPRESS device. A fast-Fourier transform algorithm was used to compute the PSD. In frequencies up to 0.5 Hz, the PSD of heart rate variability contains three major components: a low frequency (P1), a middle frequency (P2) and a high frequency (P3). Each component was normalized by dividing the absolute values by total power (T), and then used as an index of each component. Second, the effects of passive tilt, respiratory frequency and specific pharmacological sympathetic or parasympathetic blockade on the indices of these components were evaluated in the control group. The following results were obtained. 1. During passive tilt, the normalized power of P2 was increased, whereas that of P3 was decreased. 2. The peak frequency of P3 was consistent with the frequency of respiration. 3. Sympathetic blockade decreased the normalized power of P2, whereas parasympathetic blockade decreased the normalized power of P3. From these results, I concluded that the normalized power of P2 and P3 are quantitative markers of sympathetic and vagal nervous activities, respectively. Third, the results of spectral analysis in patients were compared with those in controls. The following characteristics of autonomic nervous function in vertiginous patients were noted. 1. The normalized power of P3 in patients was lower than that in controls, suggesting that parasympathetic nervous activity at rest was suppressed in patients. 2. The increase of normalized power of P2 with passive tilt was suppressed in patients, suggesting suppression of sympathetic response to passive tilt. 3. In patients with Meniere's disease, during the active period of vertigo attacks, the normalized power of P2, which is an index of sympathetic activity, was higher than that in the intervals between vertigo attacks. Fourth, with caloric stimulation in the control group, an increase of the normalized power of P2 was observed during or after the stimulation, which suggests that vestibular stimulation increases sympathetic activity. I therefore suggest the following: 1. Decreased parasympathetic activity and suppression of sympathetic response were present in the vertiginous patients. 2. Sympathetic activity was increased by vertigo attacks in the patients with Meniere's disease.

Adult↗
PubMed1986

Cotside EEG monitoring using computerised spectral analysis.

The application and interpretation of computerised spectral analysis of the neonatal electroencephalogram (EEG) using the Neuroscience Berg Fourier Analyser (BFA) is described. Recordings are immediately available at the cotside. Electrophysiological changes can be recognised by individuals with no previous experience in EEG technology. The compact nature of the analysis allows long periods of recording to be viewed within minutes. In addition to the unequivocal demonstration of both clinical and subclinical seizures, the BFA is useful in the evaluation of interseizure activity--that is, disturbance of sleep patterns, electrical output, and hemisphere asymmetry.

Brain↗
PubMed1984

Schizophrenia and spectral analysis of the visual evoked potential.

Power spectral analysis was performed on the visual evoked potentials (VEPs) recorded in response to flashes of different intensity in both unmedicated schizophrenic and normal subjects. At occipital locations (O1, O2), schizophrenics showed less power than normals in the 10-14 Hz frequency range. In the 18-22 Hz range, schizophrenics showed under-activation in the left hemisphere and over-activation in the right. At temporal locations (T3, T4), schizophrenics showed abnormal (left greater than right) hemisphere patterns of activation in 10-14 Hz and 18-22 Hz ranges. There were no group differences in relationships between power and intensity changes at vertex (Cz). The results suggest abnormal cortical-subcortical interactions during analysis of visual information in schizophrenia.

Adult↗
PubMedDate not supplied

[Spectral analysis of the cardiac rhythm of fishes].

Spectral analysis of the rhythmograms in the cod Gadus morhua callarias, plaice Pleuronectes platessa, herring Clupea harengus membras and trout Salmo gairdneri revealed complex wave structure of their cardiac rhythm. In all the species investigated, slow (0.01-0.06 Hz), intermediate (0.06-0.25 Hz) and fast (0.25-0.5 Hz) waves were recorded. It is suggested that the wave structure of cardiac rhythm reflects rather complicated relationships between functional systems regulating cardiac activity.

Animals↗
PubMed2001

Spectral analysis of visual potentials evoked by pattern-reversal checkerboard in juvenile patients with headache.

Changes in visual evoked potentials, mainly affecting the amplitude of the major positive wave, are referred to by many authors and are related to the pathophysiological basis of primary headache. We performed both transient pattern-reversal visual evoked potentials and spectral analysis by means of fast Fourier transform of 8-Hz steady-state pattern-reversal visual evoked potentials in 34 children affected with migraine (14 with aura, 20 without aura), and compared them with 14 patients with tension-type headache and 10 healthy subjects. The amplitude of the response to the transient stimulation (P100) was higher and the latency shorter in the patients with headache compared with the controls, but the difference was not statistically significant. The absolute power of the first harmonic (1F) obtained by the spectral analysis of the steady-state stimulation was increased in all the patients with headache compared with the controls, and the increase was significant in patients with migraine. These data seem to confirm the hypothesis of abnormal processing of visual input in migraineurs and could be interpreted as neurophysiological support for the theory that different headache types are related conditions. Furthermore, the spectral analysis of steady-state pattern-reversal visual evoked potentials could be proposed as a test to diagnose migraine.

Child↗
PubMed1999

Spectral analysis of graft flow for anastomotic error detection in off-pump CABG.

OBJECTIVE: Flow probes have been introduced as a non-invasive means of anastomotic quality assessment in off-pump coronary artery bypass graft (CABG). Flow waveform morphology cannot reliably be assessed visually unless severe anastomotic stenosis is present ( > 90%). We applied spectral analysis techniques to determine whether the frequency content of graft flow can improve the surgeon's ability to detect anastomotic errors. METHODS: Forty-six mammary to left anterior descending artery (LAD) anastomoses were created in mongrel dogs during off-pump CABG surgery. Graft flow was measured using transit-time flow probes with the LAD closed, and the mammary graft patent and with varying degrees of stenosis. The degree of anastomotic stenosis was created by an artificial stitch and verified by random postoperative angiography. Spectral analysis of the graft flow waveforms was performed. Differences in the magnitude and phase components of the graft flow for the first five harmonics were determined for the varying anastomosis test conditions. Differences were determined using analysis of variance and least square means techniques. RESULTS: The magnitude of the fundamental (zeroth) harmonic was statistically different in the internal mammary artery (IMA) with 0-25% stenosis compared to IMA with 50-75% stenosis (P < 0.01 ). Further, the magnitude of the first, second, and fourth harmonics were statistically different in IMA with 0-25% compared to IMA with 75% (P < 0.01). The phase of the first harmonic was statistically different in IMA with 25% stenosis than IMA with 50% stenosis (P < 0.01 ). No differences in interaction between the LAD and IMA for all ranges of stenosis were detected (P > 0.50). CONCLUSION: Spectral analysis of graft flow waveforms may be beneficial in detecting lesser degrees of anastomotic stenosis (i.e. < 90%) compared to traditional visual assessment of mean graft flow and/or graft flow waveform morphology.

Anastomosis, Surgical↗
PubMed1998

Spectral analysis of heart rate variability in patients with irritable bowel syndrome.

BACKGROUND: Autonomic dysfunction, both adrenergic and cholinergic, has been associated with the irritable bowel syndrome (IBS). The accuracy of the methods in use, however, has been limited by the need for active co-operation by the patients, with consequent difficulties in standardization. The aim of this study was to investigate the function of the autonomic nervous system in patients with IBS by using spectral analysis of the heart rate variability, an accurate method depending very little on patient cooperation. METHODS: Eighteen patients with IBS were compared with 36 sex- and age-matched controls. Spectral analysis of heart rate variability was performed to quantify sympathetic and parasympathetic nerve activity. RESULTS: The patients with IBS had significantly higher sympathetic activity than controls (P = 0.005). There was no significant (P = 0.308) increase in parasympathetic activity. There were no significant differences in heart rate or blood pressure between the patients and controls. CONCLUSION: Spectral analysis of heart rate variability has been used to assess the function of the autonomic nervous system in patients with IBS. IBS patients have significantly increased symphathetic activity, whereas parasympathetic activity does not differ from that of controls.

Adult↗
PubMed2001

Color doppler ultrasonography and spectral analysis of venous flow in diagnosis of varicocele.

OBJECTIVE: The standardization of diagnostic criteria for varicocele has not yet been established. This causes difficulty in evaluating both the incidence and clinical studies. Our aim was to establish diagnostic criteria for varicocele in Doppler procedures. METHODS: The characteristics of blood flow in the internal spermatic vein were investigated with color Doppler ultrasonography (CDU) and venous flow spectral analysis in 100 infertile men without clinical varicocele (group I), 100 infertile men with clinical left varicocele (group II), and 50 fertile men without clinical varicocele served as controls (group III). RESULTS: Three types of flow pattern were found in the spectral analysis of venous flow. If the venous flow was directed to the heart and did not change direction with an intra-abdominal pressure increase, it was classified as type I; venous flow directed to the heart, but changing direction with an intra-abdominal pressure increase, was classified as type II, and blood flow directed to the testicles and augmenting with an intra-abdominal pressure increase, was classified as type III. In group I, flow patterns were 39, 56 and 5% on the left side and 55, 42 and 3% on the right side for types I, II and III, respectively. In group II, flow patterns were 0, 35 and 65% on the left side and 61, 38 and 1% on the right side for type I, II and III patterns, respectively. In group III, the figures were 44, 54 and 2% for the left and 54, 46 and 0% for the right. Type II and III flow patterns were seen more frequently than type I in patients with clinical left varicocele (p<0.001). Whereas type I and II flow patterns were more common than type III in subjects without clinical varicocele (p<0.05). A type II flow pattern during normal breathing was seen at a lower rate in the control group than in the other groups (p<0.05). CONCLUSION: Spectral analysis of Doppler waves should be used in combination with CDU for the diagnosis of varicocele. Varicocele should not only be diagnosed with a type II flow pattern which occurs during valsalva. For the diagnosis of varicocele, the main criterion must be a type III pattern flow, as well as a type II pattern during normal breathing.

Adult↗
PubMed2005

Spectral analysis of feeding and lying behavior of cattle kept under different feedlot conditions.

This study used spectral analysis in 2 separate experiments to examine feeding and lying behavior of Bos taurus steers under 2 housing treatments: a feedlot yard stocked at 12.0 m2 per head with a dry, firm pen surface (NDF) and a "high density" (HDF) feedlot yard stocked at 6.0 m2 per head with a wet and muddy feedlot pen surface. The study conducted 1 experiment in Autumn, another in Spring. The study measured and analyzed ambient temperatures, relative humidity, and barometric pressure half-hourly onsite, using time series cross-correlations to determine whether steer behavior was associated with them. Both NDF and HDF groups showed similar lying and eating duration. HDF steers exhibited patterns of lying and feeding different from those of NDF steers. Spring observations found a number of correlations with temperature, relative humidity, and barometric pressure. Health and production data showed no differences between treatments. The results indicate that cattle made successful, short-term changes to changed feedlot environmental conditions. However, confirming these findings requires further replication. Spectral analysis was shown to be sensitive enough to detect behavioral differences between treatments and thus has potential animal welfare assessment tool.

Animal Husbandry↗
PubMed2000

Spectral analysis of left ventricular area variability as a tool to improve the understanding of cardiac autonomic control.

Spectral analysis of the fluctuations in heart rate (HR) or blood pressure (BP) has been extensively used as a tool for the noninvasive assessment of autonomic control of the heart. The recently developed echocardiographic acoustic quantification allows noninvasive continuous measurement of the left ventricular cross-sectional area (LVA) signal. In this study, we investigated whether the LVA signal, and more specifically its fluctuations, can be reliably subjected to spectral analysis, and whether the results of such analysis may improve the understanding of the cardiovascular control mechanisms. Our results show that the general pattern of power spectra of LVA fluctuations, as well as their reproducibility, is similar to the power spectra of HR and BP fluctuations. Analysis of LVA signals obtained in normal subjects at rest as well as under vagal blockade and under held respiration, and in patients with known autonomic dysfunction, showed significant differences between groups and states. The effects of age, related to the reduction in parasympathetic activity, were not evident in the spectral content of the LVA and BP signals. The high frequency LVA fluctuations are mainly of mechanical origin, since they were eliminated by breath-holding. We observed an increase in the high frequency LVA fluctuations under vagal blockade, indicating that under normal (control) conditions, these high frequency fluctuations are attenuated by parasympathetic activity. The enhancement in high frequency fluctuations in LVA observed in diabetic patients can thus be attributed to reduced parasympathetic activity. The analysis of LVA variability may be used as a tool for basic research and, possibly, as a quantitative clinical measure for specific disease states.

Adolescent↗
PubMed2001

Spectral analysis of epicardial 60-lead electrograms in dogs with 4-week-old myocardial infarction.

There were few studies on the spectral analysis of multiple-lead epicardial electrograms in chronic myocardial infarction. Spectral analysis of multi-lead epicardial electrograms was performed in 6 sham-operated dogs (N group) and 8 dogs with 4-week-old myocardial infarction (MI group). Four weeks after the ligation of left anterior descending coronary artery, fast Fourier transform was performed on 60-lead epicardial electrograms, and then inverse transform was performed on 5 frequency ranges from 0 to 250 Hz. From the QRS onset to QRS offset, the time integration of unsigned value of reconstructed waveform was calculated and displayed as AQRS maps. On 0-25 Hz AQRS map, there was no significant difference between the 2 groups. In the frequency ranges of 25-250 Hz, MI group had significantly smaller AQRS values than N group solely in the infarct zone. It was shown that high frequency potentials (25-250 Hz) within QRS complex were reduced in the infarct zone.

Animals↗
PubMed1996

Autonomic nervous function in essential hypertension in the elderly. Evaluation by power spectral analysis of heart rate variability.

Autonomic nervous function in elderly essential hypertensive patients was investigated by power spectral analysis of heart rate variability. Fifty-seven essential hypertensive patients participated in this study. They were divided into two groups: the middle-aged group (age < or = 59 years, n = 30) and the elderly group (age > or = 60 years, n = 27). All examinations were performed during hospitalization. Power spectral analysis of R-R interval was performed from Holter electrocardiogram every 10 min by the maximum entropy method to obtain the low frequency band (LFB; 0.04 to 0.15 Hz), which is an index of both sympathetic and parasympathetic nervous activity. Twenty-four-hour blood pressure measurement was performed by the cuffoscillometric method to evaluate the nocturnal decrease in blood pressure. Nondipper patients were defined as those whose nocturnal decrease in systolic blood pressure was < 10% of daytime blood pressure. Both LFB and HFB were significantly lower in elderly hypertensive patients than in middle-aged patients (P < .001 and P < .05, respectively). Elderly nondipper patients had further reduced power spectral densities throughout the day. Both LFB and HFB showed a negative correlation with age. However, the age-related decline of power densities was more prominent in dipper patients and was not statistically significant in nondipper patients. These findings indicate that the nondipper phenomenon is superimposed on age-related attenuation of autonomic nervous function in essential hypertension.

Aged↗
PubMed1997

Alteration of cardiac function in patients with temporal lobe epilepsy: different roles of EEG-ECG monitoring and spectral analysis of RR variability.

PURPOSE: Because several reports have described the relation between epilepsy and cardiac arrhythmias and suggest that changes in autonomic neural control of the heart could be involved in the pathogenesis of sudden unexplained death in patients with epilepsy, the aim of this study was to evaluate cardiac function in patients with temporal lobe epilepsy. METHODS: Sixty-five patients with epilepsy were evaluated by simultaneous ambulatory 24-h EEG-ECG monitoring, and in 30 of these, power spectral analysis of relative-risk (RR) variability also was carried out, both in the supine position and in a passive tilt position at 60 degrees. The power spectrum of RR variability, the two major spectral components detectable at low frequency (LF) and at high frequency (HF), respectively, and the LF/HF ratio were calculated. RESULTS: By EEG-ECG monitoring, we recorded six partial seizures, and in four cases, discharges were associated with sinus tachycardia. However, interictally the occurrence of ventricular and supraventricular arrhythmias was not different from that in normal subjects. The spectral analysis of RR variability, on the other hand, demonstrated in patients with epilepsy a significant decrease in the total RR variability and in both of its components (LF and HF) in the supine position, and of the LF/HF ratio in orthostatic position. CONCLUSIONS: These findings suggest that the spectral analysis of RR variability may detect disorders of autonomic cardiac control in patients with epilepsy, even in the absence of abnormal findings during ECG monitoring. This alteration, which is more severe in cases with right EEG focus, could play a role in the pathogenesis of cardiac arrhythmias.

Arrhythmias, Cardiac↗
PubMed2005

Untangling long branches: identifying conflicting phylogenetic signals using spectral analysis, neighbor-net, and consensus networks.

Long-branch attraction is a well-known source of systematic error that can mislead phylogenetic methods; it is frequently invoked post hoc, upon recovering a different tree from the one expected based on prior evidence. We demonstrate that methods that do not force the data onto a single tree, such as spectral analysis, Neighbor-Net, and consensus networks, can be used to detect conflicting signals within the data, including those caused by long-branch attraction. We illustrate this approach using a set of taxa from three unambiguously monophyletic families within the Pelecaniformes: the darters, the cormorants and shags, and the gannets and boobies. These three families are universally acknowledged as forming a monophyletic group, but the relationship between the families remains contentious. Using sequence data from three mitochondrial genes (12S, ATPase 6, and ATPase 8) we demonstrate that the relationship between these three families is difficult to resolve because they are separated by a short internal branch and there are conflicting signals due to long-branch attraction, which are confounded with nonhomogeneous sequence evolution across the different genes. Spectral analysis, Neighbor-Net, and consensus networks reveal conflicting signals regarding the placement of one of the darters, with support found for darter monophyly, but also support for a conflicting grouping with the outgroup, pelicans. Furthermore, parsimony and maximum-likelihood analyses produced different trees, with one of the two most parsimonious trees not supporting the monophyly of the darters. Monte Carlo simulations, however, were not sensitive enough to reveal long-branch attraction unless the branches are longer than those actually observed. These results indicate that spectral analysis, Neighbor-Net, and consensus networks offer a powerful approach to detecting and understanding the source of conflicting signals within phylogenetic data.

Animals↗
PubMed1996

Color Doppler ultrasound and spectral analysis of tumor vessels in the differential diagnosis of solid breast masses.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the usefulness of color Doppler and spectral analysis of specific tumor vessels in the differentiation of benign from malignant breast masses. METHODS: Forty-eight patients with solid breast masses were evaluated with color Doppler ultrasound prospectively. When tumor vessels were visualized, spectral analysis was performed and peak systolic and end diastolic Doppler frequency shifts were recorded. Histology was obtained in all but two cases. RESULTS: In 28 out of 29 malignant lesions tumor vessels were visualized. Thirteen of 19 benign lesions showed no demonstrable flow. The peak systolic Doppler frequency shifts recorded over the vessels of the malignant breast masses were significantly higher than those of the benign breast masses (P < 0.01). CONCLUSIONS: In our preliminary series, spectral Doppler analysis of tumor vessels shows promise in differentiating benign from malignant breast masses.

Biopsy, Needle↗
PubMed1991

Spectral analysis of heart rate in diabetic autonomic neuropathy. A comparison with standard tests of autonomic function.

Power spectral analysis of the heart rate was compared with standard tests of autonomic function performed on 15 insulin-dependent diabetic patients with symptoms of autonomic dysfunction. The high-frequency power, low-frequency power, and total power of the heart rate power spectrum measured in the supine position--possible measures of parasympathetic nervous system function--were significant predictors of the expiratory-inspiratory ratio, the beat-to-beat heart rate difference on deep respiration, the standard deviation of the resting heart rate, the 30:15 ratio, and the Valsalva ratio. The change in low-frequency power on moving from the supine to upright position, a possible measure of sympathetic nervous system function, was a modest predictor of the systolic and diastolic blood pressure fall in response to postural change, but a poor predictor of the blood pressure response to isometric exercise and a cold stimulus. This study supports the role of heart rate power spectral analysis as a clinical test of autonomic function in patients with known or suspected autonomic failure.

Adult↗
PubMed2006

An adaptive strategy for selecting representative calibration samples in the continuous wavelet domain for near-infrared spectral analysis.

Sample selection is often used to improve the cost-effectiveness of near-infrared (NIR) spectral analysis. When raw NIR spectra are used, however, it is not easy to select appropriate samples, because of background interference and noise. In this paper, a novel adaptive strategy based on selection of representative NIR spectra in the continuous wavelet transform (CWT) domain is described. After pretreatment with the CWT, an extension of the Kennard-Stone (EKS) algorithm was used to adaptively select the most representative NIR spectra, which were then submitted to expensive chemical measurement and multivariate calibration. With the samples selected, a PLS model was finally built for prediction. It is of great interest to find that selection of representative samples in the CWT domain, rather than raw spectra, not only effectively eliminates background interference and noise but also further reduces the number of samples required for a good calibration, resulting in a high-quality regression model that is similar to the model obtained by use of all the samples. The results indicate that the proposed method can effectively enhance the cost-effectiveness of NIR spectral analysis. The strategy proposed here can also be applied to different analytical data for multivariate calibration.

Journal Article↗
PubMed1995

Spectral analysis of stress-induced change in blood pressure and heart rate in normotensive subjects.

Changes in spectral analysis of the variability in systolic blood pressure (SBP) and heart rate (HR) were investigated in 12 normotensive volunteers during a well-standardized stress test. BP was measured indirectly from the finger by a noninvasive device (Finapres). The stress test was a computerized version of the Stroop color word conflict test (CWT). The influences of acute (single dose) beta 1-selective blockade by bisoprolol or angiotensin-converting enzyme (ACE) inhibition by lisinopril were analyzed by a double-blind placebo-controlled trial. During the placebo phase, the efficiency of the stress test was confirmed by a significant increase in SBP (25 +/- 11%), HR (36 +/- 23%), and plasma concentrations of epinephrine (Epi, 54 +/- 37%) and norepinephrine (NE, 27 +/- 35%). Stress induced a significant increase in the amplitude of SBP and HR oscillations in the medium-frequency band (MF, 70- to 140-mHz range), which corresponds to the Mayer waves (27 +/- 32 and 42 +/- 43%, respectively for SBP-MF and HR-MF). The stress-induced increase in NE correlated significantly with the increase in HR (r = 0.68, p < 0.05). The stress-induced increase in SBP-MF correlated significantly with the increase in Epi (r = 0.69, p < 0.05) and in HR-MF (r = 0.69, p < 0.05). A significant decrease in SBP-MF at rest was observed with a single oral (p.o.) dose of bisoprolol, but not of lisinopril. As a noninvasive method, spectral analysis of the variability in SBP and HR may be of benefit in stress-induced modifications of the autonomic nervous system.

Adult↗