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PubMed2001

Mechanisms of female urinary continence under stress: frequency spectrum analysis.

Intravesical and urethral pressure signals during cough and Valsalva maneuvers for 15 continent women were analyzed with frequency spectrum analysis. Clear modulation of the urethral pressure changes by the intravesical pressure rise during stress maneuvers was demonstrated in the frequency bands of 14 and 7 Hz for cough and Valsalva, respectively. The linearity between the urethral and intravesical pressure signals was strong for cough, but relatively weaker for Valsalva. The observed linearity lead to the formulation of a modified continence equation to mathematically quantify stress leak point pressure (sLPP): sLPP=MUCP/(1-alpha1)+RBP. This algebraic equation demonstrated that sLPP depends on pressure transmission, resting bladder pressure, and maximum urethral closure pressure. The equation was validated with excellent theoretical predictions for the 15 continent subjects (R(2)=0.98 and 0.97 for cough and Valsalva leak point pressure, respectively) and good but somewhat weaker predictions for 46 stress incontinent women (R(2)=0.79 and 0.48, respectively). It has been shown that pressure transmission plays the most important role in female continence function, while it may be attributable to passive structural origin as evidenced by the minimal time delay between the two pressure signals, in the order of a few milliseconds. It can be concluded that coughing seems to have a more mechanical, rather than neuromuscular basis for its signal dynamics. This study suggests that a complete assessment of female stress continence function requires comprehensive urodynamic information in terms of pressure transmission, maximum urethral closure pressure, and resting bladder pressure.

Adult↗
PubMed1996

Power spectrum analysis of EMG at different voluntary efforts in normal subjects.

BACKGROUND: In the previous studies, the results from power spectrum frequency changes at different sustained forces have been quite conflicting. This was the result of enormous changing in firing rate and motor units recruited; these were deciding factors of electromyographic power spectrum. The aim of this study was to investigate the characteristics of rate coding and electromyograph (EMG) interference pattern in two EMG-computer sets. METHODS: Thirty-nine healthy subjects were included in our study. Each was in a relaxed sitting position with forearm, wrist, and metacarpophalangeal joints fixed by straps. Two surface electrodes were attached to the muscle belly of extensor digitorum communis. EMG signals were processed at 10%, 25%, 50% and 100% of maximal voluntary contraction (MVC) using visual feedback from a dynamometer. RESULTS: The amplitude in dB remained constant at different isometric forces. The rate-coding parameters showed non-significant decrease as the percentage of MVC increased, ashereas the time-domain parameters revealed significant increase with stepwise increase in force. CONCLUSIONS: EMG power spectrum analysis provides an easy, painless way of assessing global recruitment/rate descriptions of motor units.

Adult↗
PubMed1983

Duplex ultrasound scanning of the carotid arteries with velocity spectrum analysis.

Duplex ultrasound examination of the carotid arteries using high-resolution realtime imaging and pulsed Doppler flow measurements with velocity spectrum analysis was performed on a series of 50 consecutive patients (100 vessels), and findings were compared with findings of conventional carotid arteriography. The criteria for an abnormal duplex examination included: a velocity ratio of 1.5 or more (ratio of the maximum internal carotid artery [ICA] flow velocity to the maximum common carotid artery flow velocity); turbulence, as indicated by an ICA velocity spectral width of 40 cm per second or more; visible plaque that produced an ICA stenosis of 50% or more; a maximum ICA velocity of 100 cm per second or more; and inability to detect ICA flow. A flow-limiting stenosis was defined arteriographically as a 50% or greater stenosis of the diameter of the arterial lumen. The velocity ratio was the best single duplex criterion, with an overall accuracy of 88%. The sensitivity or specificity of the duplex examination was as high as 97%, depending on the number of duplex criteria that were abnormal.

Arteriosclerosis↗
PubMedDate not supplied

Range-gated pulsed Doppler power frequency spectrum analysis for the diagnosis of carotid arterial occlusive disease.

Carotid arterial disease was investigated with a Duplex Scanner using Power Frequency Spectrum Analysis. Sixty-one carotid systems were evaluated noninvasively and angiographically, while 20 controls were examined and assumed to be normal. Peak frequency and 50% frequency bandwidth, a quantitative index of spectral broadening, were correlated with the percentage of stenosis. Peak frequency predicted the presence or absence of hemodynamically significant stenoses (greater than or equal to 50% diameter reduction) with 90.8% accuracy, while 50% frequency bandwidth correctly identified similar lesions with 93.2% accuracy (p = NS). Also, with the latter results, carotid systems were grouped into less than 25%, 25% to 49%, and greater than or equal to 50% stenosis categories with an 86.4% accuracy. Similar statistical evaluation was attempted for peak frequency results. It was not possible to separate hemodynamically insignificant lesions (less than 50% diameter reduction) into distinct groups because of the overlap of results among those arteries with less than 50% stenosis. Finally, all eight occluded internal carotid arteries were identified with combined Doppler/imaging analysis. However, with imaging alone, only 5 of 8 (63%) occluded arteries were correctly identified.

Carotid Artery Diseases↗
PubMed1990

[Effect on electroacupuncture on experimental epilepsy--power spectrum analysis of EEG].

The present study was undertaken to investigate the effect of electroacupuncture (EA) on electroconvulsive shock (ECS) and penicillin-induced convulsions in rats, using power spectrum analysis technique. Under quiet state, delta and theta bands were found to be predominant in the power spectrum of spontaneous EEG's with the peak of the main power in the delta band. During ECS and penicillin-induced convulsions, the power percentage of the delta band decreased, while those of alpha and beta bands increased. The bands with the peak of the main power shifted to the right, and the total power was distinctly enhanced. No marked change in background EEG activity was observed during EA stimulation. In the case of EA plus ECS or penicillin-induced convulsions, the power percentage of the delta band increased, while those of alpha and beta bands decreased. The peak of the main power returned to the delta band with a decreased total power. The compressed power spectrum array showed distinct suppression of convulsions by EA audio-visually. These results suggest that EA enables the EEG to synchronize and enhances the inhibitory process of the brain, thereby plays its anticonvulsant role.

Animals↗
PubMed1982

Detection of subcritical stenoses by Doppler spectrum analysis.

Little information is available regarding the sensitivity of carotid Doppler signal spectral analysis in documenting flow disturbances caused by subcritical stenotic lesions. We have studied the effects on spectra of stenoses ranging from 10% to 80% diameter reduction using the infrarenal aorta of the dog. Spectral analysis was able to reliably detect stenoses as small as 20% by comparison of the peak systolic frequency at the site of stenosis with that proximal to it; a peak frequency ratio of about 1.5 was typical for this degree of stenosis. This ratio continued to increase in the nearly linear fashion with increasing stenosis, reaching approximately 2.1 for a 50% stenosis. For greater degree of stenosis, turbulent flow patterns and significant spectral broadening were noted a gradual decrease in the peak frequency ratio. Spectra of Doppler signals recorded at sites 1 cm or more distal to the stenosis site were not significantly different from proximal spectra until the stenosis exceeded a 45% diameter reduction and the peak frequency ratio 1.3. At these distal sites this ratio increased with increasing stenosis to a maximum of 1.64 for a 65% stenosis, beyond which the flow was characterized by severe turbulence and a decreasing ratio. Doppler signal spectrum analysis appears to be a potentially quantitative noninvasive technique that has the sensitivity necessary to detect subcritical carotid arterial stenoses and be applicable to the clinical setting.

Animals↗
PubMed1991

Assessment of aortoiliac obstructive disease by Doppler spectrum analysis of blood flow velocities in the common femoral artery at rest and during reactive hyperemia.

Aortoiliac obstructive disease was assessed by Doppler spectrum analysis of blood flow velocities in the common femoral artery measured both at rest and during reactive hyperemia. The intraarterial femoral artery pressure measured at rest and during reactive hyperemia served as the "gold standard" for the definition of a hemodynamically significant aortoiliac stenosis. Our results, obtained from 93 patients (136 limbs), showed that differences between Doppler spectra obtained from limbs with a hemodynamically significant aortoiliac stenosis and those from limbs without were more pronounced during reactive hyperemia than at rest. The best assessment of aortoiliac obstructive disease could be obtained with a combination of parameters derived from Doppler spectra measured at rest and during reactive hyperemia. With these parameters, obtained by multivariate analysis, 85% of the limbs were diagnosed correctly compared with the gold standard. If angiographic data were added to the gold standard, even 91% of the limbs were diagnosed correctly. We conclude that analysis of Doppler spectra-obtained noninvasively from the common femoral artery at rest and during reactive hyperemia provides an accurate hemodynamic assessment of the aortoiliac segment.

Aortic Diseases↗
PubMed2001

Effects of slow repetitive transcranial magnetic stimulation on heart rate variability according to power spectrum analysis.

We examined whether repetitive transcranial magnetic stimulation (rTMS) at a low rate could influence autonomic function, specially heart rate variability (HRV) by power spectrum analysis. We studied 16 healthy male volunteers as a stimulation group and 16 others as a sham group. The stimulation group received magnetic stimulations from a circular coil over Cz at a frequency of 0.2 Hz and an intensity presenting 90% of the motor threshold. Experiments in both groups included four daily sessions; at each, a train of 70 stimuli was delivered over 350 s. HRV of low-frequency power (LF) in a standing position and high-frequency power (HF) in a supine position were measured before and after each session. After stimulation, HF and LF powers were significantly increased. After sham stimulation, the power of HF but not that of LF significantly increased. Neither actual nor sham stimulation produced a long-term effect detectable on day 5. The finding of transiently increased LF power following actual but not sham stimulation suggests that rTMS may activate the sympathetic nervous system.

Adult↗
PubMed1993

Non-conventional ultrasonography (power spectrum analysis) in the management of retinoblastoma.

The differential diagnosis among the diseases that may simulate retinoblastoma is supported by several techniques; however, none of them can give an undeniable answer. In the authors' opinion the tissue characterization by power spectrum analysis of the radiofrequency ultrasound data may play an important role in the backscattered signal spectrum while being sensitive to the spectral shift trend. In order to evaluate the patterns of regression of quiescence of retinoblastoma foci after conservative treatment the authors try to create a model of tissue characterization that provides information not available in conventional A & B scan ultrasonography about cell type, vascularization and necrosis.

Choroid Neoplasms↗
PubMed2000

[Power spectrum analysis of heart rate variability to orthostatic challenge in cases of Binswanger's encephalopathy].

The autonomic nerve activity was evaluated in cases of Binswanger's encephalopathy by power spectrum analysis of heart rate variability during supine rest and standing upright, in order to elucidate the role of autonomic nervous system function in the pathophysiology of Binswanger's encephalopathy. There was no difference in the ratio of low frequency (LF) power to high frequency (HF) power (L/H ratio), which reflects cardiac sympathetic nerve activity in each position among Binswanger's encephalopathy, control and lacunar stroke. Binswanger's encephalopathy had significantly lower HF power, which reflects cardiac parasympathetic nerve activity, than control and lacunar stroke in a supine rest, and HF power did not respond to standing. Moreover, there was no difference in HF power between mild cases and severe cases of Binswanger's encephalopathy, and L/H ratio decreased in severe cases during standing. These results suggest that cardiac parasympathetic nervous system function is impaired in the early stage of Binswanger's encephalopathy, then cardiac sympathetic nervous system dysfunction occurs with advancing the disease stage.

Aged↗
PubMed1996

Doppler spectrum analysis in the differential diagnosis of renal transplant dysfunction.

Cyclosporin A (CyA) nephrotoxicity and rejection of a renal allograft each demands a specific therapy. This study was designed to establish the capability of Doppler spectrum analysis to diagnose either one of these causes during renal dysfunction. Between October 1989 and October 1991 we performed echo-Doppler examinations in 209 renal transplant recipients on a routine basis during the first three months after transplantation. Echo-Doppler examinations during periods of renal dysfunction were analyzed. A total of 93 periods of renal dysfunction, retrospectively due to rejection (n = 40) or CyA toxicity (n = 53), occurred in 70 patients during the study period. A control group consisted of 82 patients with normal functioning grafts. When compared to the control group, the Doppler features (in segmental arteries) of the rejection group showed significant lower frequency shifts [Fmax (Hz) 1637 +/- 423 vs. 1436 +/- 465; p < 0.05; Fdia (Hz) 582 +/- 180 vs. 458 +/- 225; p < 0.05], a shorter deceleration time of the Doppler spectrum [Tdown (ms) 340 +/- 100 vs. 276 +/- 102; p < 0.05], and a higher Resistance Index (RI 0.64 +/- 0.08 vs. 0.68 +/- 0.13; p < 0.05). Doppler spectra during CyA toxicity showed only a significantly longer acceleration time [Tmax (ms) 123 +/- 36 vs. 139 +/- 40; p < 0.05]. The capability of differentiation between the two causes was assessed with ROC analysis of single Doppler features, stepwise regression and canonic discriminant analysis on a set of Doppler features and with manual selection of several features with extreme values. ROC analysis yielded maximum sensitivity and specificity for the diagnosis of rejection using Tdown (sensitivity 65%; specificity 68%). Stepwise regression and canonic discriminant analysis of a set of features rendered a sensitivity and specificity of 73% and 64%, respectively. Explorative selection of extreme Doppler feature values showed that 18 of the 40 grafts with rejection had values that were only seen in 2 cases with CyA toxicity (positive predictive value 90%; sensitivity 45%; specificity 96%). In half of these cases Doppler features preceded the clinical diagnosis of rejection by a median of 4 d. In conclusion, Doppler spectra are influenced by rejection and CyA toxicity in specific ways. The Doppler features, however do not enable definite differentiation between rejection and CyA toxicity in all cases. Some changes in Doppler spectra are only seen in cases of rejection and thus enable positive identification of grafts with rejection, often earlier than clinical signs indicate rejection. A normal Doppler spectrum does not exclude rejection as the cause of renal dysfunction.

Blood Flow Velocity↗
PubMed1997

Autonomic function in narcolepsy: power spectrum analysis of heart rate variability.

Ten narcoleptic patients that had never been treated previously and ten healthy volunteers of comparable age underwent 48-h polygraphic recording to assess the effects of wakefulness and sleep on beat-to-beat heart rate variability by means of power spectrum analysis. The study revealed decreased power in the low frequencies (LF) during sleep (whereby an increase of the power in this band is associated with sympathetic activation) compared with wakefulness, with minimal values during stage 3-4 non-REM sleep and higher levels during REM sleep, both in patients and controls. Significantly reduced power in high frequencies (HF; mainly expression of parasympathetic control) and a significantly increased LF/HF ratio during wakefulness before sleep in narcoleptics compared with controls were found. Our study excludes a primary disturbance of cardiac autonomic nervous system in narcoleptics but suggests an altered circadian autonomic function in these patients.

Adult↗
PubMed1986

Continuous-wave versus range-gated pulsed Doppler power frequency spectrum analysis in the detection of carotid arterial occlusive disease.

Two types of ultrasonic Doppler velocity metering devices currently used in the detection of extracranial carotid artery disease, the continuous-wave (CW) and the range-gated pulsed (RP) Doppler systems, were compared in the present study. Power frequency spectrum analysis (PFSA) was performed on 130 carotid arterial bifurcations with a CW Doppler and 81 carotid arteries with an RP Doppler system. All results were compared with angiographic findings. The frequency bandwidth at 50% peak power (f50%), a quantitative index for defining spectral broadening, detected stenoses equal to or greater than 50% diameter reduction with 93% sensitivity, 92% specificity, and 92% accuracy with the CW system. With the RP Doppler, the same degree of stenosis was identified with 94% sensitivity, 93% specificity, and 93% accuracy. Compared with angiographic classification into 0-24%, 25-49%, and 50-99% diameter reduction categories, CW Doppler PFSA and an 85% overall accuracy, and the RP Doppler overall accuracy was 86%. CW Doppler also correctly identified 15 of 16 internal carotid artery (ICA) occlusions; 8 of 8 ICA occlusions were correctly identified with the RP Doppler. Thus, both techniques detected carotid artery disease with comparable results. For research and ease of operation, an RP Doppler system with a variable sampling volume appears to be most desirable. However, a standard CW system is superior if utility and cost-effectiveness are of prime importance.

Arterial Occlusive Diseases↗
PubMed1981

Myocardial infarction diminishes both low and high frequency QRS potentials: power spectrum analysis of lead II.

Previous studies based primarily on counts of QRS notches and slurs have suggested that myocardial infarction (MI) increases high frequency QRS components. However, this technique does not quantitatively measure total high frequency voltage. To further study this problem, a microprocessor ECG system was employed capable of averaging multiple QRS complexes to reduce noise. Power spectrum analysis of the QRS using a Fast Fourier Transform was then performed in lead II in ten normal subjects and ten patients with prior inferior MI. The infarct group showed a decrease in QRS potentials over a broad frequency range (7.81-304.7 Hz). Therefore, contrary to previous estimates, MI may attenuate high as well as low frequency QRS potentials as part of a general decrease in electromotive force.

Adult↗
PubMed1989

Power spectrum analysis of myometrial electromyogram and intrauterine pressure changes in the pregnant rhesus monkey in late gestation.

Various methods have been used to quantify myometrial activity in the pregnant rhesus monkey during the last third of gestation. A precise definition of activity must retain the characteristics of epoch duration, amplitude, and the repetitive frequencies of active epochs. We used Fast Fourier Transform and power spectrum analysis to determine whether the patterns of myometrial contractility consist predominantly of contractions or contractures. This analysis allows quantification of activity represented by each of these patterns of activity. We applied these methods to myometrial electromyogram and intrauterine pressure recordings in pregnant rhesus monkeys to characterize the changes in myometrial activity that occur after surgery, after intravenous indomethacin administration, and when food is withdrawn for 48 hours. We conclude that changes in the frequency pattern of myometrial activity provide important information in relation to labor and delivery contractions.

Animals↗
PubMed1991

[Spectrum analysis of heart rate. A method of studying the role of the autonomic nervous system in the regulation of blood circulation].

Spectral analysis of heart rate variability has recently been shown to be a reliable noninvasive test for quantitative assessment of cardiovascular automatic regulatory responses. In 12 ambulant normotensive healthy young males (mean age 23 +/- 1 years) after a period of 10 min. for stabilisation, a continuous ecg recording (lead CM-5) for 8 min. was obtained in the supine and standing position, with a controlled respiration rate 15/min. Power spectrum of 512 point time series (R-R intervals) in both positions was calculated using a fast Fourier transform-based window periodogram method. Based upon results from the literature the power spectrum analysis was performed on two components: low frequency LF (0.05-0.15 Hz) and high frequency HF (0.15-0.50 Hz). Mean R-R interval decreased on standing position from 0.79 +/- 0.10 s to 0.59 +/- 0.11 s (p less than 0.001). The ratio HF/LF in supine was 0.63 +/- 0.70 and on standing position 2.54 +/- 0.73 (p less than 0.001). The relative LF component of the total HR power spectrum increased from 22.8% +/- 12.1% to 42.9 +/- 14.4% (p less than 0.001) after changing the position from supine to standing, and the relative HF component decreased from 56.3 +/- 22.4% to 25.5 +/- 16.2 (p less than 0.001). The total power was significantly lower when standing in comparison to supine position (681 +/- 519 s2, 1188 +/- 963 s2 respectively, p less than 0.05). Our results suggest that heart rate fluctuations in supine position in normal men are mainly vagally determined (HF power spectrum component).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗