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PubMed1992

Spectral analysis of short-term blood pressure and heart rate variability in uremic patients.

Short-term fluctuations in blood pressure (BP) and heart rate (HR) were quantified to assess autonomic nervous system (ANS) dysfunction in six dialysis patients, compared to six control subjects of similar age. Indirect finger BP was measured by a Finapres device. Analog-to-digital conversion of the BP was used to determine systolic BP (SBP), diastolic BP (DBP) and HR every second. The equidistant sampling allowed a direct spectral analysis using a fast Fourier transform algorithm. Uremic patients exhibited reduced BP and HR short-term variabilities, with a dramatic reduction in the amplitude of the 0.1 Hz component (Mayer waves) of SBP and DBP spectra. Dialysis did not produce any consistent immediate improvement in the amplitude of the Mayer waves. Our study thus indicates impaired cardiovascular ANS function in uremic patients.

Adult↗
PubMed1988

Spectral analysis of ventilation in elderly subjects awake and asleep.

We studied the periodicities of ventilation in elderly subjects using digital comb filtering. Two groups of subjects were studied, those with and without sleep apnea. Measurements were made in wakefulness, stage 1-2 sleep, and where possible in stage 3-4 sleep. For each of the digital filters we calculated the average power of the oscillatory output. To compare subject groups we first specifically determined the average power in the filter with the maximum output. The mean of this measurement was greater in elderly subjects with apnea compared with those without apnea, both during wakefulness and stage 1-2 sleep. In both groups of subjects the cycle time of the major ventilatory oscillations was on the order of 40-60 s. There was no difference in this cycle time between the two groups of subjects in wakefulness or stage 1-2 sleep. Thus, whereas similar oscillatory processes occur in subjects with and without apnea, it is the magnitude of the oscillation that differs between the two groups. These conclusions are supported by analysis of the output of individual filters of the digital comb filter. In both groups, stage 1-2 sleep produced significantly increased oscillations in ventilation. Both in wakefulness and stage 1-2 sleep, significantly greater periodicities occurred in the apneic compared with the nonapneic group. In the few subjects who had sufficient data in stage 3-4 sleep for spectral analysis, ventilatory oscillations were virtually absent in this state. Our data suggest that subjects who develop apnea during sleep have an increased propensity for periodic breathing even while awake.

Aged↗
PubMed1999

Nonlinear, fractal, and spectral analysis of the EEG of lizard, Gallotia galloti.

Electroencephalogram (EEG) from dorsal cortex of lizard Gallotia galloti was analyzed at different temperatures to test the presence of fractal or nonlinear structure during open (OE) and closed eyes (CE), with the aim of comparing these results with those reported for human slow-wave sleep (SWS). Two nonlinear parameters characterizing EEG complexity [correlation dimension (D2)] and predictability [largest Lyapunov exponent (lambda(1))] were calculated, and EEG spectrum and fractal exponent beta were determined via coarse graining spectral analysis. At 25 degrees C, evidence of nonlinear structure was obtained by the surrogate data test, with EEG phase space structure suggesting the presence of deterministic chaos (D2 approximately 6, lambda(1) approximately 1. 5). Both nonlinear parameters were greater in OE than in CE and for the right hemisphere in both situations. At 35 degrees C the evidence of nonlinearity was not conclusive and differences between states disappeared, whereas interhemispheric differences remained for lambda(1). Harmonic power always increased with temperature within the band 8-30 Hz, but only with OE within the band 0.3-7.5 Hz. Qualitative similarities found between lizard and human SWS EEG support the hypothesis that reptilian waking could evolve into mammalian SWS.

Animals↗
PubMed1982

Spectral analysis of the electroencephalographic response in experimental concussion in the rat.

The phenomenon of concussion was studied in 32 non-anesthetized Sprague-Dawley male rats, previously implanted with chronic epidural electrodes for bipolar recording of the electroencephalogram (EEG). EEG records were taken continuously preceding during and following concussion, which was produced by a lead-tipped dart, shot from a spring-loaded pistol. The mass and velocity of the striking instrument were measured, so that its momentum and kinetic energy could be calculated. Spectral analysis of the EEG was performed by means of computer, using Fast Fourier Transform. In stage 1-2 of concussion, the power spectra of alpha, beta, and theta frequency bands were decreased by 25%, 37% and 10%, respectively. The delta spectrum alone was increased by 15%. Stage 3-4 of concussion was characterized by more profound depression of the power spectra of alpha, beta, theta and delta frequency bands (56%, 49%, 34% and 31%, respectively). EEG depression occurred immediately, reached a peak at 5 min and recovered at an average of 2 h in the concussed rats. In 5 rats, which did not recover completely, post-mortem examination revealed cerebral contusion or intracranial hematomas. These rats were not included in the analysis of 'concussion'. The EEG changes suggest the involvement of the cerebral cortex in the traumatic unconsciousness of concussion and are similar to those of spreading depression, as noted by previous investigators.

Animals↗
PubMed2003

Cross-spectral analysis of cardiovascular parameters whilst supine may identify subjects with poor orthostatic tolerance.

An easy and low-cost method for identification of subjects prone to orthostatic vasovagal syncope would be of clinical benefit. An orthostatic test with 60 degrees head-up tilt and progressive lower-body negative pressure was performed on 79 patients with histories of unexplained syncope and 26 control subjects. The test was stopped at the onset of presyncope and time to presyncope was taken as a measure of orthostatic tolerance. Spectral and cross-spectral analysis was performed on the supine time series of the R-R interval (ECG) and systolic pressure (Finapres) recorded before the beginning of the test. According to reference values, 38 patients and 11 controls were classified as having poor orthostatic tolerance (PPT and CPT respectively), whereas 41 patients and 15 controls displayed normal orthostatic tolerance (PNT and CNT respectively). The central frequency of the low-frequency (LF approximately equal to 0.1 Hz.) oscillations in PNT and CNT was significantly higher than that in PPT and CPT. In addition, it was significantly linearly correlated with the time of presyncope. Using our test of orthostatic tolerance as a comparison, the LF central frequency allows the classification of subjects with poor or normal tolerance with 80% sensitivity and 82% specificity. These results suggest that the LF central frequency in the supine position may provide a useful index in the diagnosis of orthostatic intolerance.

Adolescent↗
PubMed1998

Colour Doppler-guided spectral analysis of gall-bladder wall flow.

For the purpose of the present study to diagnose gall-bladder cancers, which cannot be detected or are only partly visible by conventional ultrasonography (US), we attempted differential diagnoses of 69 patients with gall-bladder diseases (12 with gall-bladder cancer, five with acute cholecystitis, 11 with chronic cholecystitis, 27 with cholesterol polyp and 14 with adenomyomatosis) using the evaluation of gall-bladder wall blood flow (GWBF). GWBF was evaluated by colour Doppler-guided spectral analysis (CDSA). Thirty-three healthy volunteers were selected as controls at random. Two parameters of GWBF, namely flow velocity and resistive index (RI), were compared between patients with gall-bladder diseases and healthy volunteers. GWBF could be ultrasonically evaluated in 92 (90%) of 102 subjects. All 12 patients with gall-bladder cancer had a significantly rapid blood flow value compared with other patients and healthy volunteers. There was no significant difference in RI among patients and healthy volunteers. When cut-off level of the flow velocity was set at 30 cm/s, gall-bladder cancer could be diagnosed by flow velocity with 100% sensitivity (12/12) and 96% specificity (50/52). Using the same cut-off level of the flow velocity, 17 patients were analysed prospectively. In four asymptomatic gall-bladder cancers and two acute cholecystitis cases with some symptoms, the flow velocity was over 30 cm/s. In two of four patients with gall-bladder cancer, only a part of the tumour was visualized on conventional abdominal US. In conclusion, CDSA was more useful for diagnosing gall-bladder lesions than the conventional abdominal US due to estimation of arterial flow velocity in the gall-bladder wall.

Blood Flow Velocity↗
PubMed2002

Isotopomer spectral analysis of intermediates of cholesterol synthesis in human subjects and hepatic cells.

Steroid intermediates of the cholesterol synthesis pathway are characterized by rapid turnover rates relative to cholesterol due to their small pool size. Because the small pools will label rapidly, these intermediates may provide valuable information about the incorporation of isotopes in de novo synthesis of cholesterol and related compounds. The labeling of cholesterol synthesis intermediates from [1-(13)C]acetate was investigated in human subjects and in liver cell models by means of isotopomer spectral analysis (ISA). In human subjects, infusing [1-(13)C]acetate into the duodenum for 12 h demonstrated that approximately 50% of the plasma lathosterol pool was derived from de novo synthesis during this interval. The lipogenic acetyl-CoA precursor pool enrichment reached a constant value within 3 h of the start of the infusion. In vitro studies indicated that liver cell models decrease de novo lathosterol synthesis when cholesterol synthesis is inhibited by statins or cholesterol-containing serum. We propose a new calculation to increase the accuracy and precision of cholesterol synthesis estimates in vivo combining the ISA of lathosterol and cholesterol.

Acetates↗
PubMed1995

[A transient sinus arrest after right stellate ganglion block--assessment of autonomic function by heart rate spectral analysis].

We experienced a case of sinus arrest probably induced by right stellate ganglion block (SGB). A healthy medical student volunteered in our study of the cardiac autonomic nervous system and received the SGB. After the Holter ECG had been attached, the SGB was performed with mepivacaine 8 ml. Horner's sign was observed after about 3 minutes. A transient (15 s) sinus arrest occurred suddenly after about 6 minutes of the tilt test probably due to a vasovagal reflex, and the subject lost consciousness. From spectral analysis of the Holter ECG recording, the right SGB may be closely involved in the induction of the sinus arrest. Our present case suggests that sinus arrest may occur if a patient stands up after right SGB.

Adult↗
PubMedDate not supplied

111-Indium platelet imaging, Doppler spectral analysis and angiography compared in patients with transient cerebral ischaemia.

We have evaluated carotid gamma imaging using 111Indium-labelled platelets in the diagnosis of carotid artery disease and measured the accumulation of labelled platelets on endarterectomy specimens. Autologous 111In labelled platelets were injected in 25 patients with TIA. Gamma images were then taken daily and independently interpreted by two observers. Carotid endarterectomy was performed in 11 patients allowing measurement of the radioactivity on the operative specimen. These results were compared to the findings on angiography and Doppler spectral analysis. All endarterectomy specimens accumulated platelets with the most active equivalent to platelets from 1.8 ml blood. Atheromatous ulcers were more active than stenoses with mean (+/- SEM) activities of 1.12 +/- 0.37 and 0.38 +/- 0.10 respectively. These radioactivity levels were at the threshold of gamma camera resolution in a theoretical model. Both observers agreed that 22 of the 50 carotid bifurcations showed platelet accumulation on gamma imaging. Of the 12 atheromatous ulcers demonstrated by angiography 11 were visualized, but only five of ten stenoses greater than 80% were detected. As Doppler identified all stenoses only one angiographically diseased carotid was not detected by combining ultrasound with platelet scanning. Atherosclerotic arteries accumulate 111In platelets and the more thrombogenic ulcerated plaques are identified more frequently than stenoses. Long-term follow-up is required to establish the clinical relevance of platelet deposition.

Angiography↗
PubMed1996

The Use of Spectral Analysis of Limiting Dilution for Investigating the Immune Response.

In this study we present a method for characterizing a spectrum of cells engaged in the humoral response by two parameters: the frequency and potential activity of antigen specific precursor cells. Spleen cells from mice immunized with ovalbumin were placed in microcultures in a limiting dilution assay. The values derived from positive cultures in an activity/cell number plot were compatible with Poisson distributions for distinct families of precursor cells displaying either positive or negative (suppressor-like) activities. Proposed limiting dilution spectral analysis combines the potentialities of the standard limiting dilution analysis with those provided by histograms of distribution according to the activity of positive cultures. This method opens new opportunities in detecting and characterizing distinct groups of limiting precursor cells.

Journal Article↗
PubMed2002

Visual and spectral analysis of sleep EEG in acute hemispheric stroke.

BACKGROUND: Reports on the effects of focal hemispheric damage on sleep EEG are rare and contradictory. PATIENTS AND METHODS: Twenty patients (mean age +/- SD 53 +/- 14 years) with a first acute hemispheric stroke and no sleep apnea were studied. Stroke severity [National Institute of Health Stroke Scale (NIHSS)], volume (diffusion-weighted brain MRI), and short-term outcome (Rankin score) were assessed. Within the first 8 days after stroke onset, 1-3 sleep EEG recordings per patient were performed. Sleep scoring and spectral analysis were based on the central derivation of the healthy hemisphere. Data were compared with those of 10 age-matched and gender-matched hospitalized controls with no brain damage and no sleep apnea. RESULTS: Stroke patients had higher amounts of wakefulness after sleep onset (112 +/- 53 min vs. 60 +/- 38 min, p < 0.05) and a lower sleep efficiency (76 +/- 10% vs. 86 +/- 8%, p < 0.05) than controls. Time spent in slow-wave sleep (SWS) and rapid eye movement (REM) sleep and total sleep time were lower in stroke patients, but differences were not significant. A positive correlation was found between the amount of SWS and stroke volume (r = 0.79). The slow-wave activity (SWA) ratio NREM sleep/wakefulness was lower in patients than in controls (p < 0.05), and correlated with NIHSS (r = -0.47). CONCLUSION: Acute hemispheric stroke is accompanied by alterations of sleep EEG over the healthy hemisphere that correlate with stroke volume and outcome. The increased SWA during wakefulness and SWS over the healthy hemisphere contralaterally to large strokes may reflect neuronal hypometabolism induced transhemispherically (diaschisis).

Electroencephalography↗
PubMed1995

[Spatial distribution of high-frequency components in the terminal QRS complex in patients with ventricular tachycardia and previous myocardial infarction--comparison of late potential map and spectral analysis].

It is clinically important to predict the ventricular tachycardia (VT) for the prognosis in patients with previous myocardial infarction. Low-amplitude high-frequency components observed at the end of QRS complex, termed "late potentials" are associated with VT. The use of signal-averaged body surface mapping technique enabled us to study spatial distributions of high-frequency components in the QRS terminal portion. In this paper, we investigated body surface distributions of high-frequency components in the terminal QRS complex, compared with late potential map and spectral analysis. Signal-averaged body surface mapping will provide new electrical information regarding understanding of the high-frequency components in the QRS complex.

Body Surface Potential Mapping↗
PubMed1987

Spectral analysis of twin time series designs.

The genetic analysis of physiological time series has to accommodate the presence of autocorrelation. This can be accomplished by means of orthogonal transformation of the series, thus enabling the use of standard genetic analysis techniques for the sequence of uncorrelated transforms. In view of the oscillatory character which typifies various physiological time series, it is customary to invoke spectral techniques for the analysis of these series. It can be shown that spectral analysis is an orthogonal transformation that asymptotically resembles principal component analysis. Consequently, standard genetic analysis methods for the uncorrelated spectral transforms may be used. This approach will be illustrated with simulated and real (heart rate) data for univariate twin time series. Furthermore, it will be indicated that the proposed analysis can be readily generalized to multivariate time series.

Electrocardiography↗
PubMed2000

Cyclic alternating pattern and spectral analysis of heart rate variability during normal sleep.

The natural arousal rhythm of non-rapid eye movement (NREM) sleep is known as the cyclic alternating pattern (CAP), which consists of arousal-related phasic events (Phase A) that periodically interrupt the tonic theta/delta activities of NREM sleep (Phase B). The complementary condition, i.e. non-CAP (NCAP), consists of a rhythmic electroencephalogram background with few, randomly distributed arousal-related phasic events. Recently, some relation between CAP and autonomic function has been preliminarily reported during sleep in young adults by means of spectral analysis of heart rate variability (HRV). The present study was aimed at analysing the effects of CAP on HRV in a group of normal children and adolescents. Six normal children and adolescents (age range 10.0-17.5 y) were included in this study. All-night polygraphic recordings were performed after adaptation to the sleep laboratory. Six 5-min epochs were selected from sleep Stage 2 and six from Stages 3 and 4 (slow-wave sleep), both in CAP and NCAP conditions. From such epochs, a series of parameters describing HRV was then calculated, in both time and frequency domains, on the electrocardiographic R-R intervals. Statistical comparison between CAP and NCAP epochs revealed a significant difference for most of the frequency domain parameters (increase of the low-frequency band, increase of the low-frequency/high-frequency ratio and decrease in the high-frequency band during CAP) both in Stage 2 and in slow-wave sleep. Our results demonstrate that the physiological fluctuations of arousal during sleep described as CAP are accompanied by subtle, but significant, changes in balance between the sympathetic and vagal components of the autonomic system.

Adolescent↗
PubMed1995

Molecular heterogeneity of PAF in normal human mixed saliva: quantitative mass spectral analysis after direct derivatization of PAF with pentafluorobenzoic anhydride.

Platelet-activating factor (PAF), a family of phospholipid autacoids with potent pro-inflammatory activities, is present in saliva. The current study has quantitated various species of PAF isolated from normal human mixed saliva. Choline-containing, sn-2 acetylated phospholipids with sn-1 ether- or ester-linked fatty alcohol/acid moieties (alkyl-PAF or acyl-PAF, respectively) were evaluated after direct derivatization with pentafluorobenzoic (PFB) anhydride. Individual species of PFB-derivatized PAF were separated by gas chromatography prior to mass spectral analysis; quantitative estimates of six different species of PAF in saliva were made by comparison to corresponding authentic, synthetic PAF standards. In each saliva sample, all six species of PAF were readily detected by this facile procedure. The predominant PAF was 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine or 16:0-alkyl-PAF (0.75 +/- 0.09 pmol/ml saliva; mean +/- S.E.; n = 5) which represented only 30.4 +/- 1.5% of the total PAF. Substantial amounts of 18:1- and 18:0-alkyl-PAF and 16:0-acyl-PAF were also identified (0.52 +/- 0.07, 0.35 +/- 0.06, and 0.35 +/- 0.02 pmol/ml saliva, respectively). In summary, mass spectrometric analysis of PAF after direct derivatization with PFB anhydride has revealed that at least six different species of PAF are present in normal human mixed saliva. This structural diversity may represent an important aspect of homeostasis in the healthy oral cavity.

Anhydrides↗
PubMed1999

Cardiac autonomic adjustments to normal human pregnancy: insight from spectral analysis of R-R interval and systolic arterial pressure variability.

OBJECTIVE: To assess the adaptation in autonomic control mechanisms that accompanies the marked haemodynamic changes, such as increases in cardiac size and output, that occur in the course of normal human pregnancy. DESIGN: We studied 14 healthy pregnant women (aged 30+/-1 years) before the 6th week (early stage) and within weeks 32-34 (late stage) of pregnancy, while they were at rest or in a state of active orthostatism (standing), which enhances sympathetic activity. METHODS: We used echocardiography to assess cardiac volumes and mass, and spectral analysis of the R-R interval and systolic arterial pressure variability to obtain indices of autonomic regulation of the circulation. This non-invasive methodology, recently validated with direct recordings of muscle sympathetic nerve activity, furnishes quantitative markers of sympathetic modulation of the sino-atrial node (low frequency component, LF in normalized units, nu), vagal modulation (high frequency component, HF in normalized units, nu) and the overall arterial pressure-heart rate baroreflex gain (alpha index). RESULTS: Late pregnancy was characterized by an increase in cardiac size and volumes and by a reduction of R-R interval, R-R interval variance and the alpha index, together with an increase in the LF/HF ratio (from 1.4+/-0.4 to 5.6+/-1.9). Changes in markers of autonomic modulation of the sino-atrial node normally induced by the standing position were blunted. CONCLUSIONS: The late stage of normal human pregnancy appears to be characterized by alterations in the autonomic control of the circulation and by attenuated responsiveness to active standing, possibly as a consequence of the accompanying increase in cardiac size.

Adult↗
PubMed1998

[Alterations in postural control: the use of spectral analysis in stability measurement].

UNLABELLED: Static posturography studies the frequency at which the center of gravity in the human body oscillates. There is no universal agreement as to the importance of this index or whether it is specific in identifying alterations in the postural control systems (vestibular, proprioceptive and visual). Nevertheless, some hypotheses appear generally accepted: a) visual information dominates; b) proprioception affects anterior-posterior oscillation; c) relatively low frequency body oscillation is affected by vestibular input while higher frequency oscillations are controlled by proprioceptive information. In order to check these hypotheses, four groups of patients underwent spectral analysis of bodily oscillations recorded with static posturography. The four groups of patients were similar in terms of age and broken down as follows: Group A-peripheral diabetic neuropathy (10 cases); Group B-diabetic neuropathy-free patients (10 cases); Group C-pure peripheral vestibulopathy (10 cases); Group D-normal subjects (20 cases). Analysis was performed dividing the frequency spectrum (FFT) into three groups: gr. I) 0.01-0.7 Hz; gr. II) 0.7-1 Hz; gr. III) > 1 Hz. Analysis of the spectra for Group A showed a significant increase in high frequency bodily oscillation (gr. III) with the eyes open in the anterior-posterior direction (M = 8.6 +/- 5.5; p < 0.05) and in the lateral direction (M = 4.0 +/- 2.0; p < 0.05); an increase was also found in both directions with the eyes closed (M = OCX II: 7.4 +/- 1.5; p < 0.05) (M = OCX III: 5.6 +/- 1.6; p < 0.01) (M = OCY II: 16.8 +/- 5.0; p < 0.05) (M = OCY II: 9.2 +/- 4.4; p < 0.05). In Group B the increase was limited to high frequency anterior-posterior oscillations (gr. III) at open eyes (M = 3.6 +/- 1.6; p < 0.05) and at closed eyes (M = 4.4 +/- 1.5; p < 0.05). In Group C there was an increase in high frequency lateral oscillations (gr. III) at open eyes (M = 4.2 +/- 0.5; p < 0.01) and panfrequency oscillations at closed eyes (M = OCX I: 47.7 +/- 5.6; p < 0.01) (M = OCX II: 23.2 +/- 4.9; p < 0.01) (M = OCX III: 7.2 +/- 2.3; p < 0.05). CONCLUSIONS: The diabetic proprioceptive deficit appears to lead to multiplanar destabilization at the medium-to-high frequency range. The labyrinthine deficit, on the other hand, appears to cause lateral destabilization at all frequencies. The method of analysis used appears to provide useful parameters with which to evaluate static posture since they can specifically identify alterations in orthostatic bodily control of various origins.

Adult↗
PubMed1989

Importance of spectral analysis indices for assessment of the grade of stenosis of the arteria carotis interna.

The authors evaluated the indices of Doppler power frequency spectrum analysis in 106 patients with suspected extracranial carotid occlusive disease. Blackshear, Norrving and Knox indices appeared to be most sensitive for identification of the grade of stenosis of the arteria carotis interna. Sensitivity of ultrasound examination was correlated with angiography. The highest sensitivity (90%), specificity (100%), and overal accuracy (97%) were recorded in the group of hemodynamic significances disturbances of ACI, i.e. high stenoses with occlusions. Calculation of indices of spectral analysis has been performed routinely in all non-invasive ultrasound examinations of carotid arteries by means of Echoflow method.

Carotid Artery Thrombosis↗