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At least 613 records · Page 34Linked to original sources
PubMedDate not supplied

Power spectral analysis of heart rate variability in psychiatry.

Power spectrum analysis of heart rate variability (PSA of HRV) is a promising method, which can be used as an index of cardiac autonomic balance. PSA of HRV is a noninvasive technique, based on ECG sampling of RR interval variation, thus providing a dynamic assessment of sympathetic and parasympathetic tone, reflecting the interactions between the two. It has been shown to have potential value in various laboratory and clinical conditions. It is influenced by many factors such as age, sex, position, breathing, smoking, hour of the day and medications. Different methods of data processing by various authors have often elicited conflicting results. Standard values are not yet available to be used or compared in different settings. From the interest it has raised, it may be expected that this method will be in widespread use in clinical practice in the future, providing a useful tool, both for diagnostic and prognostic purposes, as well as serving as a further aid towards monitoring therapeutic interventions. This review highlights techniques of dynamic assessment of HRV and studies of its clinical applications in psychiatry in particular. It raises the potentially important prognostic implications of protracted autonomic dysfunction in psychiatric patient populations, especially for cardiovascular morbidity and mortality.

Analysis of Variance↗
PubMed1979

[Technical and methodological aspects concerning the application of Fourier's analysis to phonocardiography (author's transl)].

The frequency spectrum analysis (Fourier's analysis) has recently been applied to phonocardiography. Using this mathematical approach instead of the current empirical analysis, it is possible to obtain -- on a less subjective basis -- more precise pathophysiological and diagnostic information from the acoustic cardiac phenomena. On the other hand, this refinement of the method of analysis stresses the need for better technical and methodological solutions, in order to reach the standardization of both the transduction and the recording of the acoustic signal at higher level of sensibility, fidelity and reproducibility. With this in mind, and on the basis of their experience, the Authors suggest the adoption of devices with specific technical characteristics, and propose a suitable method of application of Fourier's analysis to the phonocardiogram.

Fourier Analysis↗
PubMed2002

Quantitative analysis of tryptophan analogue incorporation in recombinant proteins.

Three different methods to quantitate tryptophan (Trp) analogue incorporation into recombinant proteins are described: first, spectroscopic analysis based on a linear combination of the absorption spectra of the aromatic residues in the denatured Trp-containing or analogue-substituted protein; second, chromatographic separation of analogue-substituted and Trp-containing proteins by HPLC; and third, mass spectrum analysis of the mixture of analogue-substituted and Trp-containing proteins. An accurate estimate of analogue incorporation in single-Trp proteins can be obtained directly by either analysis of the absorption spectrum or HPLC chromatography. While analysis of the absorption spectrum or HPLC chromatogram can provide an assessment of the average level of analogue incorporation for proteins that contain two or more Trp residues, mass spectroscopy analysis of peptides generated by protease digestion and separated by HPLC provides a general method for a complete quantitative description of the distribution of analogue incorporation. The more complex analysis by mass spectroscopy becomes important for multi-Trp proteins because the distribution of analogue versus Trp-containing polypeptide chains may not be the same as that predicted on the basis of average level of analogue incorporation.

Chromatography, High Pressure Liquid↗
PubMed2000

Effects of breathing control on cardiocirculatory modulation in Caucasian lowlanders and Himalayan Sherpas.

This study was performed to investigate the influence of breathing control on the autonomic cardiac regulation at high altitude in adapted and non-adapted awake subjects. We recorded electrocardiogram and pulse oximetry in 14 short-term acclimatized lowlanders and 14 Himalayan Sherpas during resting conditions at an altitude of 5,050 m. Spectrum analysis was performed on synchronized 15 min periods of R-R intervals and the oxygen saturation of arterial blood (SaO2). Despite mean SaO2 being similar in lowlanders and Himalayan Sherpas [78.5 (SD 7.0)% compared to 79.4 (SD5.8)%, respectively], fluctuations in SaO2 were significantly increased in lowlanders compared to Sherpas, thus indicating an unstable regulation of respiration control in lowlanders. Regression analysis demonstrated a significant relationship between spectrum power of SaO2 and the relative power of R-R intervals in the frequency band between 0.01 and 0.08 Hz in lowlanders, but not in Sherpas. Our results demonstrate differences in respiratory and autonomic cardiac control between non-adapted lowlanders and Himalayan high-altitude residents and indicate that unstable breathing control during chronic hypobaric hypoxia is significantly correlated with the autonomic cardiocirculatory regulation.

Acclimatization↗
PubMed1990

Enhanced vasomotion of cerebral arterioles in spontaneously hypertensive rats.

Intrinsic rhythmic changes in the diameter of pial cerebral arterioles (30-70 microns) in anesthetized normotensive and hypertensive rats were assessed in vivo to determine if any significant differences exist between the two strains. All diameter measurements were analyzed using a traditional graphic analysis technique and a new frequency spectrum analysis technique known as the Prony Spectral Line Estimator. Graphic analysis of the data revealed that spontaneously hypertensive rats (SHR) possess a significantly greater fundamental frequency (5.57 +/- 0.28 cycles/min) of vasomotion compared to the control Wistar-Kyoto normotensive rats (WKY) (1.95 +/- 0.37 cycles/min). Furthermore, the SHR cerebral arterioles exhibited a significantly greater amplitude of vasomotion (10.07 +/- 0.70 microns) when compared to the WKY cerebral arterioles of the same diameter (8.10 +/- 0.70 microns). Diameter measurements processed with the Prony technique revealed that the fundamental frequency of vasomotion in SHR cerebral arterioles (6.14 +/- 0.39 cycles/min) was also significantly greater than that of the WKY cerebral arterioles (2.99 +/- 0.42 cycles/min). The mean amplitudes of vasomotion in the SHR and WKY strains obtained by the Prony analysis were found not to be statistically significant in contrast to the graphic analysis of the vasomotion amplitude of the arterioles. In addition, the Prony system was able to consistently uncover a very low frequency of vasomotion in both strains of rats that was typically less than 1 cycle/min and was not significantly different between the two strains. The amplitude of this slow frequency was also not significantly different between the two strains. The amplitude of the slow frequency of vasomotion (less than 1 cycle/min) was not different from the amplitude of the higher frequency (2-6 cycles/min) vasomotion by Prony or graphic analysis. These data suggest that a fundamental intrinsic defect exists in the spontaneously hypertensive rat that may contribute to the pathogenesis of hypertension in these animals.

Animals↗
PubMed1988

Computer discrimination of atrial fibrillation and regular atrial rhythms from intra-atrial electrograms.

Reliable detection of atrial fibrillation from intra-atrial data is an important requirement for automatic implantable anti-tachycardia devices. Simultaneous filtered and unfiltered intra-atrial electrograms were recorded from patients in regular rhythms (12 sinus rhythms and six regular atrial tachycardias) and atrial fibrillation (nine rhythms). Each rhythm was broken down into consecutive 4-second data segments for analysis by atrial rate calculation, power spectrum analysis and amplitude probability density function generation. Significant differences were found between regular rhythms and atrial fibrillation for atrial rate, for the percentage of the total power in the 4-9 hertz band and for amplitude probability density close to the isoelectric region. There was no overlap for any of these three parameters. For each method of analysis, algorithms were generated to discriminate individual data segments from regular rhythms and atrial fibrillation with high sensitivity and specificity. Comparable results were found when sinus rhythm was excluded from the analysis. Characteristics of intra-atrial recordings during atrial fibrillation were remarkably similar to previously published reports of intra-ventricular recordings during ventricular fibrillation. Each of the three methods of analysis may provide an algorithm for accurate detection of atrial fibrillation by anti-tachycardia devices.

Algorithms↗
PubMed2005

Application of classical and model-based spectral methods to describe the state of alertness in EEG.

Electrophysiological recordings are considered a reliable method of assessing a person's alertness. Sleep medicine is asked to offer objective methods to measure daytime alertness, tiredness and sleepiness. In this study, EEG signals recorded from 30 subjects were processed by PC-computer using classical and model-based methods. The classical method (fast Fourier transform) and three model-based methods (Burg autoregresse, moving average, least-squares modified Yule-Walker autoregressive moving average methods) were selected for processing EEG signals to discriminate the alertness level of subject. Power spectra of EEG signals were obtained by using these spectrum analysis techniques. These EEG spectra were then used to compare the applied methods in terms of their frequency resolution and the effects in determination of vigilance state of subject. It is found that, FFT and MA methods have low spectral resolution, these two methods are not appropriate for the analysis of the a wake-sleep correlation. Burg AR and least-squares modified Yule-Walker ARMA methods' performance characteristics have been found extremely valuable for the determination of vigilance state of a healthy subject, because of their clear spectra.

Adolescent↗
PubMed2003

Application of classical and model-based spectral methods to ophthalmic arterial Doppler signals with uveitis disease.

In this study, Doppler signals recorded from ophthalmic artery of 75 subjects were processed by PC-computer using classical and model-based methods. The classical method (fast Fourier transform) and three model-based methods (Burg autoregressive, moving average, least-squares modified Yule-Walker autoregressive moving average methods) were selected for processing ophthalmic arterial Doppler signals with uveitis disease. Doppler power spectra of ophthalmic arterial Doppler signals were obtained by using these spectrum analysis techniques. The variations in the shape of the Doppler spectra as a function of time were presented in the form of sonograms in order to obtain medical information. These Doppler spectra and sonograms were then used to compare the applied methods in terms of their frequency resolution and the effects in determination of uveitis disease.

Adolescent↗
PubMed1998

Are there subgroups within the autistic spectrum? A cluster analysis of a group of children with autistic spectrum disorders.

Comprehensive data on the developmental history and current behaviours of a large sample of high-functioning individuals with diagnoses of autism, Asperger's syndrome, or other related disorder were collected via parent interviews. This provided the basis for a taxonomic analysis to search for subgroups. Most participants also completed theory of mind tasks. Three clusters or subgroups were obtained; these differed on theory of mind performance and on verbal abilities. Although subgroups were identified which bore some relationship to clinical differentiation of autistic, Asperger syndrome, and Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS) cases, the nature of the differences between them appeared strongly related to ability variables. Examination of the kinds of behaviours that differentiated the groups suggested that a spectrum of autistic disorders on which children differ primarily in term of degrees of social and cognitive impairments could explain the findings.

Adolescent↗
PubMed1996

Carbonate in struvite stone detected in Raman spectra compared with infrared spectra and X-ray diffraction.

BACKGROUND: In regard to identify the compositions of urinary stones, the infrared spectra is a contemporary routine method. However, it is difficult to detect the absorption of carbonate in struvite stone by infrared spectra, because NH4 absorption of magnesium ammonium phosphate overlaps CO3 absorption of carbonate at 1420-1435 cm-1. With the purpose of demonstrating the existence of carbonate in struvite stones, the analysis of these stones by means of Raman spectra has been tried. METHODS: Forty urinary stones, the chemical compositions of which were previously determined by infrared spectroscopy, were submitted to Raman spectrum analysis, and subsequently to analysis by x-ray diffraction. RESULTS: Thirty of 40 urinary stones were found to be composed of struvite and of mixed struvite-calcium oxalate by infrared analysis. Twelve of these stones were shown to have Raman spectra of magnesium ammonium phosphate, and the other stones to have spectra of apatite. By x-ray diffraction magnesium ammonium phosphate crystals were detected in 25 of these struvite stones and hydroxyl-apatite in another 3, and 2 cases were undeterminable. For other components, such as calcium oxalate, uric acid and cystine, the analytical results of infrared spectra coincided with those of Raman spectra and x-ray diffraction. Carbonate was detected in only a part of one struvite stone by Raman spectra. CONCLUSIONS: Above-mentioned results may indicate that carbonate is only a minor component of urinary stones. Therefore, most of 1420-1435 cm-1 bands on the infrared spectra of struvite stones do not indicate CO3 absorption of carbonate, but NH(4) absorption of magnesium ammonium phosphate.

Calcium Oxalate↗
PubMedDate not supplied

Influence of contralateral obstructions on Doppler-frequency spectral analysis of ipsilateral stenoses of the carotid arteries.

Contralateral obstructions have been suggested to be responsible for inaccuracy in Doppler sonographic diagnosis and estimation of severity of internal carotid artery stenoses. Therefore correlations of the systolic peak frequency of the internal carotid artery (Doppler-Frequency-Spectrum-Analysis) and severity of stenoses found by angiography have been compared in subgroups with (n = 36) and without (n = 48) additional contralateral obstructions. The linear regressions in both subgroups were found to be very similar (Y = 0.0098X - 12.4 and Y = 0.0099X - 14.0), the coefficients of correlation identical (r = 0.83). In 26 patients, the systolic peak frequency of the internal carotid artery did not demonstrate a significant change due to operation of the contralateral vascular lesion; thus indicating that contralateral obstructions do not influence CW-Doppler sonographic findings of an ipsilateral vessel wall lesion concerning diagnostic accuracy and non-invasive estimation of the severity of stenoses.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Elastic scattering spectroscopy for intraoperative determination of sentinel lymph node status in the breast.

The ability to provide the best treatment for breast cancer depends on establishing whether or not the cancer has spread to the lymph nodes under the arm. Conventional assessment requires tissue removal, preparation, and expert microscopic interpretation. In this study, elastic scattering spectroscopy (ESS) is used to interrogate excised nodes with pulsed broadband illumination and collection of the backscattered light. Multiple spectra are taken from 139 excised nodes (53 containing cancer) in 68 patients, and spectral analysis is performed using a combination of principal component analysis and linear discriminant analysis to correlate the spectra with conventional histology. The data are divided into training and test sets. In test sets containing spectra from only normal nodes and nodes with complete replacement by cancer, ESS detects the spectra from cancerous nodes with 84% sensitivity and 91% specificity (per-spectrum analysis). In test sets that included normal nodes and nodes with partial as well as complete replacement by cancer, ESS detects the nodes with cancer with an average sensitivity of 75% and specificity of 89% (per-node analysis). These results are comparable to those from conventional touch imprint cytology and frozen section histology, but do not require an expert pathologist for interpretation. With automation of the technique, results could be made available almost instantaneously. ESS is a promising technique for the rapid, accurate, and straightforward detection of metastases in excised sentinel lymph nodes.

Algorithms↗
PubMed2003

Comparison of eigenvector methods with classical and model-based methods in analysis of internal carotid arterial Doppler signals.

Doppler ultrasound is known as a reliable technique, which demonstrates the flow characteristics and resistance of arteries in various vascular disease. In this study, internal carotid arterial Doppler signals recorded from 105 subjects were processed by PC-computer using classical, model-based, and eigenvector methods. The classical method (fast Fourier transform), two model-based methods (Burg autoregressive, least-squares modified Yule-Walker autoregressive moving average methods), and three eigenvector methods (Pisarenko, multiple signal classification, and Minimum-Norm methods) were selected for processing internal carotid arterial Doppler signals. Doppler power spectra of internal carotid arterial Doppler signals were obtained using these spectrum analysis techniques. The variations in the shape of the Doppler power spectra were examined in order to obtain medical information. These power spectra were then used to compare the applied methods in terms of their frequency resolution and the effects in determination of stenosis and occlusion in internal carotid arteries.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Cross-power spectral density analysis of pursuit tracking. Evaluation of central and peripheral pathology.

Twenty-one normal subjects were evaluated for pursuit tracking performance at frequencies of .2, .4, .8, 1.2 and 1.6 Hz. Measures of phase (lead or lag of target), gain (amplitude of response) and spectral purity (distortion of smooth tracking) were obtained by a cross-power spectrum analysis of the stimulus input and the eye movement output. It was determined that normal subjects could quite adequately track a target moving at .4 Hz. After establishing this parameter for normals, 43 patients with central and peripheral pathology related to the vestibulo-oculomotor system were tested at this frequency. Data revealed that not only central lesions but also peripheral labyrinthine impairment could cause a marked decrement in pursuit tracking ability. Also, marked changes in tracking were evident following both central and peripheral surgical procedures.

Adolescent↗
PubMed1986

Thyrotropin--an episodically secreted hormone.

A recently developed highly sensitive immunoradiometric thyrotropin (TSH) assay capable to distinguish between euthyroid and hyperthyroid TSH-levels was used to evaluate the secretion-pattern of TSH in 10 healthy male subjects by taking blood via an indwelling venous catheter at 10 min intervals over 24 h. Visual analysis revealed a pulsatile pattern of hormone release with an average of 10.3 peaks/24 h. Evaluation by computer assisted programs such as the Santen-program (8.9 peaks/24 h, amplitude 0.60 mU TSH/l), the 'Pulsar'-program (6 peaks/24 h, amplitude 0.61 mU TSH/l) or power-spectrum analysis (11.9 peaks/24 h) showed similar results. These data suggest a pulsatile mechanism of TSH secretion similar to other pituitary hormones.

Adult↗
PubMed2004

Time-series pattern changes related to movement rate in synchronized human tapping.

We investigated the effect of movement rate on the time-series properties of human synchronization errors by applying power spectrum analysis and detrended fluctuation analysis (DFA). Participants were required to execute a finger-tapping task with their right index finger in synchrony with periodic sounds under seven conditions of movement rates ranging from 1 to 4 Hz and separated by 0.5 Hz. At slow movement rates (1 and 1.5 Hz), the power spectrum of the synchronization errors flattened in the low-frequency portion, resulting in short-range correlation. At fast movement rates (from 2 to 4 Hz), on the other hand, the time series of the timing errors exhibited a 1/fbeta-type long-range correlation. These results indicate that the movement rate has an effect on the temporal coordination pattern in the human timing control mechanism. We inferred that this change in the coordination pattern reflects the transition between different states in human synchronization movements with an external signal.

Adult↗
PubMed1984

The radiolabeled microsphere technique in gut blood flow measurement--current practice.

Measurement of blood flow to the gut has become an integral part of the physiologic study of the gastrointestinal tract. While many methods have been utilized in measuring tissue blood flow, the one most often practiced today is dependent on injection of radioactively labeled microspheres. The theoretical basis of the microsphere technique is analogous to that of the indicator-dilution method. A bolus of microspheres suspended in a suitable vehicle is injected into the left atrium or left ventricle where they mix uniformly with the oxygenated blood. They are then distributed via aortic blood flow to the capillary beds within each organ in proportion to the volume of microsphere-containing blood. Technical aspects of tissue processing, gamma energy detection, and gamma spectrum analysis are reviewed. Sources of experimental error and techniques for their reduction are also discussed.

Animals↗
PubMed1999

Recording the evoked canine detrusor electromyogram.

With increasing interest in detrusor disorders and possible detrusor myopathies, a method for recording the detrusor electromyogram (detrusor-EMG) would probably greatly assist the diagnosis of various bladder dysfunctions. Therefore, we investigated the electromyographic activity of the detrusor during sacral root stimulation and during spontaneous bladder contractions in six anesthetized dogs. In all experiments, a high correlation of detrusor-EMG recordings with bladder contraction was observed. Analysis in the time domain and power spectrum analysis revealed the most clear correlation of detrusor-EMG with intravesical pressure rise in a frequency band above 3 Hz. The spike duration was 100 to 250 ms with an amplitude of 100 to 500 microV. Low-frequency activity below 1 Hz was mainly presumed to be artifacts due to fluid movement under the electrode. Our trials indicate that smooth muscle EMG recordings from the detrusor smooth musculature are possible. The exact physiological relevance of the signal in the sub-Hertz domain (<1 Hz) is still uncertain. The presented animal model allows the pathophysiologic investigation of various pathologies of bladder dysfunction and detrusor myopathies. Neurourol. Urodynam. 18:687-695, 1999.

Animals↗