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At least 505 records · Page 28Linked to original sources
PubMed2001

Long-term average spectrum (LTAS) analysis of sex- and gender-related differences in children's voices.

Long-term average spectrum (LTAS) analysis offers representative information on voice timbre providing spectral information averaged over time. It is particularly useful when persistent spectral features are under investigation. The aim of this study was to compare perceived sex of children to the LTAS analysis of their audio signals. A total of 320 children, aged between 3 and 12 years, were recorded singing a song. In an earlier analysis, the recorded voices were evaluated with respect to perceived and actual sex by experienced listeners. From this group, a subgroup of 59 children (30 boys and 29 girls) was selected. The mean LTAS revealed a peak at 5 kHz for children perceived with confidence as boys, and a flat spectrum at 5 kHz for children perceived confidently as girls (whether male or female in actuality).

Child↗
PubMed1987

Bradycardia associated with hiatal hernia and gastroesophageal reflux relieved by surgery.

A man known to have familial dysautonomia presented with a cardiac arrhythmia due to development of hiatal hernia and gastroesophageal reflux. Preoperative symptoms and assessment are described including use of power spectrum analysis of heart rate fluctuations which was consistent with enhanced parasympathetic stimulation. After surgical repair of hiatal hernia and fundoplication, bradycardia resolved, gastroesophageal reflux symptoms subsided, and the power spectrum analysis of heart rate confirmed decreased parasympathetic influence. Power spectrum analysis proved to be a useful adjunct in confirming preoperative autonomic imbalance and assessing the postoperative result. It is concluded that in individuals with disorders such as familial dysautonomia that are associated with autonomic dysfunction, cardiac arrhythmias may be a sign of esophageal pathology. Thus, cardiac evaluations should be accompanied by investigation of gastroesophageal structure and function and appropriate treatment may prevent a catastrophic arrhythmia.

Adult↗
PubMed1993

Noninvasive hemodynamic assessment of the internal mammary artery in myocardial revascularization.

Using transthoracic B-mode imaging and Doppler spectrum analysis it was found that the luminal diameter of the internal mammary artery and its hemodynamics were not significantly different among 15 preoperative patients (64 +/- 10 years) who underwent myocardial revascularization using the left internal mammary artery and young and older control groups (25 +/- 3 years and 61 +/- 9 years, respectively). These data indicate that older age does not significantly adversely influence the degree of intimal thickening and compliance in the internal mammary artery. Doppler spectrum analysis of the internal mammary artery in the patients who were operated on revealed conversion from a triphasic systolic waveform preoperatively to a unidirectional combined systolic/diastolic waveform at 1 week and 2 and 6 months postoperatively, characterized by a significant increase in the diastolic blood flow velocity and a significant decrease in the systolic blood flow velocity and the pulsatility and resistance indices. This study indicates that transthoracic B-mode imaging and Doppler spectrum analysis are promising noninvasive techniques in the preoperative assessment of internal mammary artery morphology and physiology. In addition, Doppler spectrum analysis can also be used in the long-term serial assessment of the internal mammary artery conduit after myocardial revascularization.

Adult↗
PubMed1993

"Holoprosencephaly-polydactyly" (pseudotrisomy 13) syndrome: expansion of the phenotypic spectrum.

Analysis of familial cases of the so called "holoprosencephaly-polydactyly" ("pseudotrisomy 13") syndrome shows that neither holoprosencephaly, nor polydactyly are obligatory manifestations of this condition. This review of previous case reports shows that each of these anomalies is only found in approximately 60% of affected sibs, and therefore these sentinel abnormalities are not required for diagnosis. We propose a widening of the phenotypic spectrum of this syndrome and consideration of the use of an eponomic name, such as the Cohen-Gorlin syndrome, or clear recognition that the sentinel findings of holoprosencephaly and polydactyly are not essential for diagnosis. We propose the following diagnostic criteria for the syndrome. The diagnostic criteria for sporadic cases would include a normal karyotype and either (1) a combination of holoprosencephaly and post-axial polydactyly with or without other characteristics, or (2) a combination of holoprosencephaly with other characteristics but without polydactyly, or (3) a combination of postaxial polydactyly, brain defects (microcephaly, hydrocephaly, agenesis of corpus callosum) and other characteristics. The diagnostic criteria for the familial cases would be the same, except that, as long as the other sibs have no abnormalities contradicting the diagnosis, a normal karyotype would be required in only one affected sib.

Abnormalities, Multiple↗
PubMed2003

A new computerized analysis to precisely evaluate heart rate variability during the nonstress test.

The study was conducted to assess whether the power spectrum analysis of fetal heart rate (FHR) data obtained with a cardiotocograph provides more than visual judgment of nonstress test (NST) tracing to predict fetal well-being. A total of 71 FHR data were obtained from 44 healthy pregnant women with normally grown fetuses and 11 pregnant women with pregnancy-induced hypertension. Power spectrum analysis was performed for the 8192 points of the instantaneous heart rates derived from these FHR data. Abnormal perinatal outcome was defined when at least one of the followings were present at birth: Cesarean delivery for nonreassuring FHR pattern and umbilical artery cord PH < or = 7.15, delivery at < or = 32 weeks for fetal compromise, neonatal seizures within the first 72 hours of life, respiratory distress at 36 weeks or more, 5-minute Apgar score < 7 and stillbirth. The total power of the 8192 points without considering gestational weeks was 256.3 +/- 65.6 normalized units (NU) . Hz in the fetuses with good outcomes (n = 47), while that of the abnormal fetuses (n = 8) was 148.5 +/- 54.6 NU . Hz. There is a significant difference between the two values (p < 0.00001). When the abnormal value of the total power of the 8192 points was defined as < 200 NU . Hz, the sensitivity on the prediction of fetal outcome using this method was 81.8%, significantly higher than that of the nonstress test tracing (p < 0.05). The power spectrum analysis of the large amount of FHR data obtained with a cardiotocograph permits a better assessment of the fetal well-being and may be suitable for the screening test because of no additional manpower to the current NST.

Adult↗
PubMed2006

Tadalafil and modifications in peak systolic velocity (Doppler spectrum dynamic analysis) in the cavernosal arteries of patients with type 2 diabetes after continuous tadalafil treatment.

AIM: In this study peak systolic velocity (PSV) was measured by penile duplex Doppler spectrum dynamic analysis in diabetic patients with erectile dysfunction (ED) administered continuous treatment with tadalafil for 3 months in a weekly regimen (Monday-Wednesday-Friday). Responses to the Structured Interview on Erectile Dysfunction (SIEDY) questionnaire and hormonal blood levels (LH, testosterone, prolactin) were studied before and after treatment. METHODS: The study sample was 20 diabetic patients (mean age 60 years; range 55-65) with organic vascular arterial ED at enrollment into the study. All patients were eligible for receiving tadalafil. Patients were randomly assigned to 2 different treatment groups according to a computer-generated list. The first random set of numbers was assigned to group A, the second to group B. Group A (n=10) received tadalafil 20 mg per os on demand for 3 months (Cialis, Lilly ICOS; London, UK). Group B (n=10) received tadalafil 20 mg per os on weekly fixed days (Monday-Wednesday-Friday) for 3 months. All patients underwent duplex penile sonographic dynamic evaluation after intracavernosal injection of alprostadil 20 microg (Caverject, Pharmacia SpA; Milan, Italy); SIEDY questionnaire responses and changes in blood hormonal levels (LH, testosterone, prolactin) before and after treatment were compared. RESULTS: Increased PSV at 10 min and 20 min after alprostadil administration was found in 30% of Group A patients and in 60% of Group B patients. In 40% of Group B patients, the increase in PSV was so significant as to justify reclassification to a less severe diagnostic category (Benson classification) in vascular profile. No changes in hormonal levels after treatment were found in either group. Analysis of the questionnaires showed a more marked reduction in the global total scores in Group B, with a greater frequency and a clearer improvement in global scores. CONCLUSIONS: This study on a group of 20 patients with organic vascular arterial ED disclosed at least 2 basic aspects: 1) a higher percentage of Group B patients (fixed-day treatment regimen) showed a greater improvement in PSV than the controls; 40% of these patients were reclassified according to the Benson classification; 2) within the context of a clinical study, monitoring and supportive care to increase the frequency and quality of sexual intercourse led to a resumption of and a greater interest in sexual activity. This finding cannot be explained by changes in hormonal levels; instead, there appeared a sort of effect placebo that the continuous therapy, like conventional treatment for other health reasons, had on the patient.

Aged↗
PubMed2002

Role of advanced 2 and 3-dimensional ultrasound for detecting prostate cancer.

PURPOSE: We explored the clinical usefulness of spectrum analysis and neural networks for classifying prostate tissue and identifying prostate cancer in patients undergoing transrectal ultrasound for diagnostic or therapeutic reasons. MATERIALS AND METHODS: Data on a cohort of 215 patients who underwent transrectal ultrasound guided prostate biopsies at Memorial-Sloan Kettering Cancer Center, New York, New York were included in this study. Radio frequency data necessary for 2 and 3-dimensional (D) computer reconstruction of the prostate were digitally recorded at transrectal ultrasound and prostate biopsy. The data were spectrally processed and 2-D tissue typing images were generated based on a pre-trained neural network classification. We used manually masked 2-D tissue images as building blocks for generating 3-D tissue images and the images were tissue type color coded using custom software. Radio frequency data on the study cohort were analyzed for cancer probability using the data set pre-trained by neural network methods and compared with conventional B-mode imaging. ROC curves were generated for the 2 methods using biopsy results as the gold standard. RESULTS: The mean area under the ROC curve plus or minus SEM for detecting prostate cancer for the conventional B-mode and neural network methods was 0.66 +/- 0.03 and 0.80 +/- 0.05, respectively. Sensitivity and specificity for detecting prostate cancer by the neural network method were significantly increased compared with conventional B-mode imaging. In addition, the 2 and 3-D prostate images provided excellent visual identification of areas with a higher likelihood of cancer. CONCLUSIONS: Spectrum analysis could significantly improve the detection and evaluation of prostate cancer. Routine real-time application of spectrum analysis may significantly decrease the number of false-negative biopsies and improve the detection of prostate cancer at transrectal ultrasound guided prostate biopsy. It may also provide improved identification of prostate cancer foci during therapeutic intervention, such as brachytherapy, external beam radiotherapy or cryotherapy. In addition, 2 and 3-D images with prostate cancer foci specifically identified can help surgical planning and may in the distant future be an additional reliable noninvasive method of selecting patients for prostate biopsy.

Area Under Curve↗
PubMedDate not supplied

Fatigue of the knee extensor muscles following eccentric exercise.

The purposes of this study were to determine the time course of muscle fatigue in the knee extensor muscles following an eccentric exercise protocol, and to determine if the position of the subjects during assessment affected the measurement of muscle fatigue. Twenty-four female subjects were assigned to three groups. All subjects completed baseline measure (pre-exercise test) of a power spectrum analysis of the vastus medialis, rectus femoris and vastus lateralis muscles. Following an exercise protocol of 300 eccentric repetitions of the knee extensors, power spectrum analysis was repeated at two, four, 20, 24, 48 and 72 hours for group one, at 0 hour (immediately following the exercise) and two hours for group two, and at 0 hour for group three. Groups one and two were tested in sitting, while group three was tested supine. The slope of the median frequency of the vastus lateralis muscle changed significantly over time (p < 0.001) for group one, but there were no significant changes in the slope of the median frequency of the vastus medialis muscle, while the rectus femoris muscle showed an increase in the slope of the median frequency when the subjects were in the sitting position. Further testing, in supine (group three), indicated that the position of the hip joint influenced the power spectrum analysis of the rectus femoris muscle but not the vasti muscles. In addition, fatigue occurred immediately post-exercise with recovery within 24 hours.

Adult↗
PubMedDate not supplied

Evaluation of the vagal-sympathetic interaction in diabetics with autonomic neuropathy through power spectrum density analysis of the heart rate. A critical revision of the natural history of diabetic autonomic neuropathy is possible.

In this paper we apply spectral analysis methods to heart rate variability to assess the autonomic nervous system activity in normal subjects and in patients affected by different degrees of diabetic autonomic neuropathy. The current opinion, based on different clinical tests, is that parasympathetic impairment occurs earlier in autonomic dysfunctions. However, the use of power spectrum density analysis based on a single parameter (heart rate) suggests a simultaneous involvement of parasympathetic and sympathetic pathways leading to the conclusion that perhaps the natural history of diabetic autonomic neuropathy should be substantially rewritten.

Autonomic Nervous System Diseases↗
PubMed1984

[Echotomography and spectral analysis of the Doppler signal in the assessment of carotid lesions].

Real-time echography and C.W. Doppler examination with spectrum analysis are the two methods most widely used for the study of the circulation. Echography allows the detection and the localization of the atheromatous defects whereas Doppler examination provides information on the blood flow. With the help of the frequency analysis of the Doppler signal it is possible to study much more accurately the local haemodynamic conditions. Spectrum analysis is one of the possible display mode for the Doppler signal. It provides in comparison with the zero crossing mode, much more haemodynamic parameters on the blood flow, such as velocity spectrum, density of red cells on each velocity... In this study, we tried to demonstrate that a relationship exists between the amplitude of the spectrum disturbances, recorded just after a stenosis and the degree of this stenosis. For that we propose a classification of the spectrum disturbances in five grades, each of them being related to an interval of possible values for the stenosis degree (grade I----stenosis less than 40% in area, grade II----40-60% stenosis, grade III----60-75% stenosis (extended defects) grade IV----70-90% (extended defects) and 60-90% short stenosis. Grade V: stenosis greater than 90%. The results provided by this classification were compared to those obtained by measurements of the stenosis degree on the piece of endarterectomy (72 cases). The results were in agreement in 94% of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriosclerosis↗
PubMed1991

Why do we compute the spectra?

Mechanisms underlying biological phenomena are often understood on the basis of equivalent electric circuits. An effective way of probing a biological system is to measure a signal which is a reflection of the phenomena and to analyze it according to the conventional recipe, for instance, the spectrum analysis. In this paper the meaning of spectrum analysis of a biological signal is briefly discussed in connection with linear system identification. Wiener analysis of a non-linear system is also mentioned.

Electric Conductivity↗
PubMed1997

Chaotic dynamics of sea clutter.

The notion that a deterministic nonlinear dynamical system (with relatively few degrees of freedom) can display aperiodic behavior has a strong bearing on sea clutter characterization: random-looking sea clutter may be the outcome of a chaotic process. This new approach envisages deterministic rules for the underlying sea clutter dynamics, in contrast to the stochastic approach where sea clutter is viewed as a random process with a large number of degrees of freedom. In this paper, we demonstrate, convincingly for the first time, the chaotic dynamics of sea clutter. We say so on the basis of results obtained using radar data collected from a series of extensive and thorough experiments, which have been carried out with ground-truthed sea clutter data sets at three different sites. The study includes correlation dimension analysis (based on the maximum likelihood principle) and Lyapunov spectrum analysis. The Lyapunov (Kaplan-Yorke) dimension, which is a byproduct of Lyapunov spectrum analysis, shows that it is indeed a good estimator of the correlation dimension. The Lyapunov spectrum also reveals that sea clutter is produced by a coupled system of nonlinear differential equations of order five or six. (c) 1997 American Institute of Physics.

Journal Article↗
PubMed2004

Functional changes in autonomic nervous system and baroreceptor reflex induced by 14 days of 6 degrees head-down bed rest.

We studied the effects of 14 days of 6 degrees head-down bed rest (HDBR) in 16 healthy male subjects to examine the functional changes in the autonomic nervous system and cardiac baroreceptor reflex response with an emphasis on dynamic changes during HDBR. Beat-by-beat RR intervals (RRIs) and systolic arterial pressures (SAPs) were measured non-invasively from simultaneous, continuous recordings of ECG and arterial pressure waves in supine resting postures. A power spectrum analysis by the fast Fourier transform was applied to a data set composed of interpolated 512 RRIs and 512 SAPs (256 s in duration). Three indices of cardiac baroreceptor reflex sensitivity (BRS) were obtained by applying a sequence technique and a cross-spectrum analysis technique to the spontaneous RRIs and SAPs. The high-frequency band power of RRI variability (HF(RRI)) decreased significantly in the latter part of HDBR and persisted until the initial stage of the post-HDBR period (POST). The low-frequency band power of SAP variability decreased significantly only during the mid-part of HDBR. The BRS(sequence) obtained by the sequence technique showed a significant increase temporarily on the initial day of HDBR. The BRS(sequence) and the estimate of BRS obtained by the cross-spectrum analysis handling the high-frequency band were both significantly decreased on the initial day of POST. Each of the BRS estimates correlated negatively with heart rate and positively with HF(RRI) during HDBR and POST. These results suggest the following: (1) cardiac spontaneous baroreceptor reflex sensitivity might be transiently increased at the initial stage of HDBR, (2) the reduction in vagal modulation on the sinus node occurs from the latter part of HDBR to the initial stage of POST, (3) sympathetic vasomotor control is probably slightly inhibited during the mid-part of HDBR, and (4) the enhancement in cardiac sympathetic modulation and the impairment in cardiac spontaneous baroreceptor reflex sensitivity may occur in the initial stage of POST.

Adaptation, Physiological↗
PubMed1998

Sympathetic nervous system representation in time and frequency domain indices of heart rate variability.

This study evaluated the contributions of sympathetic and parasympathetic modulation to heart rate variability during situations in which vagal and sympathetic tone predominated. In a placebo-controlled, randomized, double blind blockade study, six young healthy male individuals received propranolol (0.2 mg x kg(-1)), atropine (0.04 mg x kg(-1)), propranolol plus atropine, or placebo infusions over 4 days. Time-domain indices were calculated during 40 min of rest and 20 min of exercise at 70% of maximal exercise intensity. Spectrum analysis, using fast Fourier transformation, was also performed at rest and during the exercise. The time-domain indices standard deviation of R-R intervals, mean of the standard deviations of all R-R intervals for all 5-min segments, percentage of number of pairs of adjacent R-R intervals differing by more than 50 ms, and square root of the mean of the sum of squares of differences between adjacent R-R intervals were reduced after atropine and propranolol plus atropine. Propranolol alone caused no appreciable change in any of the time-domain indices. At rest, all spectrum components were similar after placebo and propranolol infusions, but following parasympathetic and double autonomic blockade there was a reduction in all components of the spectrum analysis, except for the low:high ratio. During exercise, partial and double blockade did not change significantly any of the spectrum components. Thus, time and frequency-domain indices of heart rate variability were able to detect vagal activity, but could not detect sympathetic activity. During exercise, spectrum analysis is not capable of evaluating autonomic modulation of heart rate.

Adult↗
PubMed1994

Cardiovascular autonomic modulation in essential hypertension. Effect of tilting.

To better understand the role played by the autonomic nervous system in essential hypertension, we used autoregressive power spectrum analysis to study the noncasual oscillations in RR interval, blood pressure, and skin blood flow in 40 subjects with mild to moderate hypertension and in 25 age-matched control subjects at low frequency (index of sympathetic activity to the heart and the peripheral circulation) and high frequency, respiratory related (index of vagal tone to the heart). RR interval, respiration, noninvasive systolic blood pressure, and skin arteriolar blood flow were simultaneously and continuously recorded with subjects in the supine position and immediately after tilting. The low-frequency component was not significantly different in the two groups either at the cardiac level (control versus hypertensive subjects: 39.1 +/- 4.3 versus 39.9 +/- 3.7 normalized units [NU]) or at the vascular level (1.52 +/- 0.17 versus 1.69 +/- 0.13 ln mm Hg2). After head-up tilting, the RR interval fluctuations were less in hypertensive subjects (low-frequency components from 39.9 +/- 3.7 to 48.4 +/- 4.1 NU, P < .05; high-frequency components from 53.9 +/- 3.7 to 44 +/- 4 NU, P < .05) than in control subjects (low-frequency components from 39.1 +/- 4.3 to 64.4 +/- 4.9 NU, P < .001; high-frequency components from 56.0 +/- 4.5 to 31.2 +/- 4.6 NU, P < .001); the low-frequency components in systolic blood pressure increased similarly in hypertensive subjects (to 2.43 +/- 0.17 ln mm Hg2, P < .0001) and in control subjects (to 2.44 +/- 0.21 ln mm Hg2, P < .01), but the low-frequency components in skin blood flow increased only in control subjects (from 5.34 +/- 0.45 to 6.55 +/- 0.53 mm Hg2, P < .01), not in hypertensive subjects (from 5.55 +/- 0.34 to 5.60 +/- 0.35 ln mm Hg2). In hypertensive subjects with left ventricular hypertrophy, the low-frequency components in systolic blood pressure did not increase after tilting (from 1.75 +/- 0.33 to 2.05 +/- 0.41 ln mm Hg2). Baroreflex sensitivity, as assessed by spectrum analysis, was significantly lower in hypertensive than in control subjects (5.17 +/- 0.49 versus 13.18 +/- 2.44 ms/mm Hg, P < .001. Power spectrum analysis did not reveal an increased sympathetic activity or reactivity either at the cardiac or at the vascular level. The decreased baroreceptor sensitivity in hypertensive subjects could explain the reduced change in sympathovagal balance in the tilt position at the cardiac level. In hypertensive subjects without left ventricular hypertrophy, cardiopulmonary reflex deactivation induced by tilting and/or amplification of sympathetic nervous tone by arteriolar structural change could have preserved the sympathetic activation at the vascular level.

Adolescent↗
PubMed1997

Tobacco smoke influence on heart rate, body temperature, and locomotor activity daily rhythms as assessed by radiotelemetry in rats.

Using radiotelemetry, this study aimed to evaluate the influence of tobacco smoke on heart rate (H), body temperature (T) and locomotor activity (A) daily rhythms in rats. The tobacco smoke intoxication was produced with a smoking apparatus. H, T, and A data were captured by radiotelemetry. The study was divided into three periods: a 1-week control period (P1), a 1-week stress period (P2), in order to evaluate the stress induced by the animals' restraint in the smoking apparatus, and a 1-week daily tobacco smoke intoxication period (P3). For P1, P2, and P3, a power spectrum analysis was applied in order to determine the dominant period of rhythmicity. Then, characteristics of the rhythms were determined by cosinor analysis. Statistical comparisons were done by ANOVA. Power spectrum analysis showed that neither stress nor tobacco suppressed the daily rhythmicity. Cosinor revealed some modifications: H amplitude was decreased during P2 and P3 with a greater reduction during P3, while T and A amplitudes were decreased during P2 and P3 without difference between P2 and P3. T acrophase was delayed during P2, while A acrophase was delayed during P2 and P3 without any difference between P2 and P3. These perturbations may reflect the effects of stress and tobacco on the suprachiasmatic nucleus by a dopaminergic mechanism.

Analysis of Variance↗