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PubMed1986

The muscle activity spectrum: spectral analysis of muscle force as an estimator of overall motor unit activity.

Starting from the observation that the part above 6 Hz of the power spectrum of force tremor during isometric contractions can be related to the unfused twitches of motor units firing asynchronously, an attempt was made to study the usefulness of force tremor spectral analysis as a global descriptor of motoneurone pool activity. To compensate for the mechanical low-pass filter characteristic of skeletal muscle which leads to increased damping of mechanical ripples at higher frequencies, a numerical compensation rule was derived from data obtained by electrical microstimulation of small ensembles of motor units (MUs). Hidden line plots of consecutive partially overlapping spectra allowed visualization of changes in spectral composition during ongoing muscle activity. The resulting muscle activity spectra (MAS) showed broad peaks according to the range of onset firing rates in normal subjects. These tended to shift to higher frequencies with increasing force. Under conditions with increased synchronization of the MUs these broad peaks were replaced by sharp peaks corresponding to the burst repetition rate. Patients with different motor dysfunctions were selected to illustrate how alterations of MU activity are reflected in the MAS. Decreased or increased firing rates were observed as well as abnormal states of synchronization. It is concluded that the MAS provides useful information about some aspects of the discharge characteristics of ensembles of MUs and therefore represents a method to monitor some qualitative 'image' of the MU activities within a muscle.

Adolescent↗
PubMed1987

Pulsed Doppler frequency and carotid stenosis.

Two hundred and forty-two internal carotid arteries (ICA) were evaluated by independently interpreted arteriography and pulsed Doppler spectrum analysis using ultrasonic arteriography to evaluate the ability of peak systolic frequency (PSF) to predict the degree of internal carotid stenosis. Mean PSF in the 129 (53.3%) high grade ICA stenoses of greater than 50% diameter reduction was 6.55 +/- 0.14 (SEM) khz, while mean PSF in the 113 (46.7%) low grade (less than 50% diameter reduction) stenoses was 3.38 +/- 0.12 (SEM) kHz (P less than 0.0001). Receiver-operator characteristic (ROC) analysis revealed that PSFs of 4.5 kHz (sensitivity 87%, specificity 88%) and 5.0 kHz (sensitivity 83%, specificity 93%) were best for identifying a 50% diameter stenosis. Positive predictive value of 5.0 kHz was 93% (107/115) and negative predictive value was 82.7% (105/127). Linear regression analysis of PSF in kHz versus percentage diameter reduction yielded the equation: % stenosis = 10.7 (PSF) - 4.1 (r = 0.76). A nonlinear equation was also derived: % stenosis = 61.9 - 33.5 (PSF) + 8.7 (PSF)2 - 0.5 (PSF)3 (r = 0.77). Based on this analysis peak systolic frequency criteria measured by pulsed Doppler spectrum analysis appear to be useful for distinguishing high grade from low grade stenoses. Both the linear and nonlinear equations further suggest that PSF can more precisely quantitate the degree of ICA luminal narrowing.

Carotid Artery Diseases↗
PubMed2003

Disorders of the larynx.

The upper respiratory tract is a frequent cause of exercise intolerance in horses, particularly in racing horses. There are a myriad of laryngeal abnormalities that may restrict airflow at the rima glottidis. Careful endoscopic examination is a crucial part of the examination of any racing horse suffering from poor performance. There has recently been interest in spectrum analysis of respiratory sounds. It has been determined that laryngeal hemiplegia and dorsal displacement of the soft palate have unique sound patterns. Therefore, spectrum analysis of respiratory sounds may prove to be useful in the diagnosis of laryngeal disorders in horses. Accurate diagnosis and appropriate surgical intervention are necessary to provide the horse the best chance of returning to its full athletic potential.

Animals↗
PubMed1999

Pitfalls in the analysis of electrogastrographic recordings.

Electrogastrography (EGG) is a noninvasive method to study gastric myoelectrical activity in humans. Because frequency characteristics are the most reliable parameters and visual analysis of the EGG recordings is notoriously difficult, automated frequency analysis, especially running spectrum analysis, is often used. However, EGG frequency spectra can be misinterpreted easily. Movement artifacts and noise from various sources can result in abnormal frequency spectra with significant power in the low-frequency and high-frequency range, or even make the EGG completely uninterpretable. Signals that differ from a sinusoid waveform have harmonics in the high-frequency range of the spectrum and may be interpreted as abnormal. Visual inspection of raw signals and frequency spectra remains essential in the analysis of EGG signals. The value of computerized analysis should not be overrated. EGG is an important research tool, but a clinical role still needs to be established.

Animals↗
PubMed1999

Chaotic dynamics in circulation with Tohoku University vibrating flow pump.

For the development of a totally implantable ventricular assist system (VAS), we have been developing the vibrating flow pump (VFP), which can generate oscillated blood flow with a relative high frequency (10-50 Hz) for a totally implantable system. In this study, the effects of left ventricular assistance with this unique oscillated blood flow were analyzed by the use of nonlinear mathematics for evaluation as the whole circulatory regulatory system, not as the decomposed parts of the system. Left heart bypasses using the VFP from the left atrium to the descending aorta were performed in chronic animal experiments using healthy adult goats. The ECG, arterial blood pressure, VFP pump flow, and the flow of the descending aorta were recorded in the data recorder during awake conditions and analyzed in a personal computer system through an A-D convertor. By the use of nonlinear mathematics, time series data were embedded into the phase space, the Lyapunov numerical method, fractal dimension analysis, and power spectrum analysis were performed to evaluate nonlinear dynamics. During left ventricular assistance with the VFP, Mayer wave fluctuations were decreased in the power spectrum, the fractal dimension of the hemodynamics was significantly decreased, and peripheral vascular resistance was significantly decreased. These results suggest that nonlinear dynamics, which mediate the cardiovascular dynamics, may be affected during left ventricular (LV) bypass with oscillated flow. The decreased power of the Mayer wave in the spectrum caused the limit cycle attractor of the hemodynamics and decreased peripheral resistance. Decreased sympathetic discharges may be the origin of the decreased Mayer wave and fractal dimension. These nonlinear dynamic analyses may be useful to design optimal VAS control.

Analog-Digital Conversion↗
PubMed1997

Nonlinear mathematical analysis of the hemodynamic parameters during left ventricular assistance with oscillated blood flow.

For the development of a totally implantable ventricular assist system (VAS), we have been developing the vibrating flow pump (VFP), which can generate oscillated blood flow with a relatively high frequency (10-50 Hz) for a totally implantable system. In this study, effects of left ventricular assistance with this unique oscillated blood flow were analyzed by nonlinear mathematics for evaluation as the entire circulatory regulatory system, not as a separate part of the system. Left heart bypasses using VFPs from the left atriums to the descending aortas were performed in chronic animal experiments using healthy adult goats. Electrocardiogram (ECG), arterial blood pressure, VFP pump flow, and flow of the descending aorta data taken while the goats were awake were recorded in the data recorder and analyzed in the personal computer system through the AD convertor. Using nonlinear mathematics, time series data were embedded into the phase space, and the Lyapunov numerical method, fractal dimension analysis, and power spectrum analysis were performed to evaluate the nonlinear dynamics. During left ventricular assistance with the VFP, Mayer wave fluctuations were decreased in the power spectrum, the fractal dimension of the hemodynamics was significantly decreased, and peripheral vascular resistance was significantly decreased. These results suggest that nonlinear dynamics, which mediate the cardiovascular dynamics, may be affected during LV bypass with oscillated flow. Decreased power of the Mayer wave in the spectrum caused the limit cycle attractor of the hemodynamics and decreased the peripheral resistance. Decreased sympathetic discharges may be the origin of the decreased Mayer wave and fractal dimension. These nonlinear dynamical analyses may be useful to design the optimal VAS control.

Animals↗
PubMed2002

[The influence of respiratory insufficiency on autonomic nervous system function in infants].

The aim of the study was to examine the influence of the respiratory insufficiency in infants treated conservatively or with the use of mechanical lung ventilation, on cardiovascular activity of the autonomic nervous system and interdependence of the sympathic and parasympathic system in infants. The cardiovascular autonomic nervous system functions were estimated by the power spectrum analysis of the heart rate variability (PS/HRV) using MEDEA HRV system. HRV spectrum analysis was limited to low (LF: 0.05-0.2 Hz) and high (HF: 0.2-0.6 Hz) frequency components, which were indicators of the sinoatrial node modulation by sympathic (LF) or parasympathic (HF) nervous system. LF/HF ratio presents the independence of the sympathic and parasympathic nervous system activity, and the total power spectrum of the HRV is the whole vegetative system activity index. The medical research was carried out in 44 infants. They included 29 infants with respiratory insufficiency conservatively treated in intensive care unit and 15 healthy control subjects. All infants with respiratory insufficiency were examined twice: during respiratory insufficiency and after recovery (40-64 days from first examination). Healthy infants were examined only once. According to the HRV parameters analysis it was proved that in infants respiratory insufficiency has significant influence on the increased cardiovascular activity of the parasympathic system, and increased cardiovascular activity of the autonomic nervous system. Respiratory insufficiency significantly changes relationship between cardiovascular activity of the sympathic and parasympathic nervous system. Regression of respiratory insufficiency symptoms causes the normalisation of both sympathic and parasympathic activity.

Autonomic Nervous System↗
PubMed1993

Computer simulations in comparison with in vivo measurements of nifedipine-induced changes in renal allograft hemodynamics.

Analysis of Doppler spectrum waveforms is increasingly used in the differential diagnosis of human renal allograft dysfunction. The physiologic interpretation of changes in Doppler spectra obtained from renal allografts, however, remains a major problem. Computer simulation models of the renal circulation may provide insight into the physiologic mechanisms responsible for changes in Doppler spectrum characteristics. The results of measurements of renal allograft hemodynamics with both determinations of PAH clearance and Doppler spectrum analysis in 11 kidney allograft recipients were explained physiologically using a computer simulation model of kidney allograft hemodynamics. Using PAH clearance and blood pressure measurements a significant decrease in RVR was found (from 0.32 +/- 0.17 to 0.20 +/- 0.07 mm Hg x min/ml, P < 0.05) after administration of the vasodilatory drug nifedipine. The Doppler spectrum waveform obtained from interlobar renal arteries showed a decrease in the RI (from 0.60 +/- 0.04 to 0.56 +/- 0.06; P < 0.05) and Tmax (from 133 +/- 32 to 98 +/- 32 ms; P < 0.05). The user-designed simulation model of renal hemodynamics showed comparable changes of the waveform when, in the model, the analogs of blood pressure, impedance of the artery, and the impedance of the peripheral vascular bed were altered proportionally.

Administration, Oral↗
PubMed1976

Power spectrum of the respiratory system.

Spectrum analysis is proposed as a method for analyzing biologic time series data that arise in the study of respiration. A mechanical model of the respiratory system is used to provide a theoretical basis for the interpretation of the air flow spectrum in terms of a physically defined energy concept. We show that under certain conditions the flow variance is proportional to the mechanical work of breathing, and indicate how this new parameter is related to conventional measures of respiratory function. An example is presented to describe the computational procedure and to illustrate the graphical aspects of cross-spectrum analysis.

Adult↗
PubMed2000

Electromyographic evidence of subclinical myopathy in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is due to a number of mutations of contractile protein genes such as beta-cardiac myosin, myosin binding protein-C, and troponin-T. Unlike troponin-T, beta-myosin is a constituent of slow skeletal muscle and its mutations generally have a better prognosis. In order to investigate the usefulness of electromyography in detecting skeletal muscle involvement in HCM, 46 patients were examined using both conventional electromyography (EMG) and quantitative electromyography (QEMG) methods. The QEMG involved motor unit potential (MUP) analysis, turns/amplitude (TAA) analysis, and power spectrum analysis of the interference pattern. Using conventional EMG, myopathic findings were demonstrated in 13 patients (28%). Receiver operating characteristic (ROC) analysis of the results of a discriminant function extracted using QEMG values, identified correctly 10 out of 11 normal controls and all 9 myopathic control patients, and displayed a 15% presence of myopathy (7 patients) among the cardiomyopathy group. The duration of MUPs was the most sensitive among the quantitative parameters in differentiating normal from myopathic subjects. Since skeletal muscle involvement may be due to distinct gene mutations, normal and myopathic EMG findings may reflect HCM subpopulations with a different genetic substrate.

Adolescent↗
PubMed1993

Ligand-induced conformation change in folate-binding protein.

C.d. and fluorescence spectroscopy have been used to investigate the effect of ligand binding on the structure and stability of folate-binding protein (FBP) from cow's whey. The c.d. spectrum of unligated FBP predicts the following secondary structure: 22% helix, 25% antiparallel beta-strand, 5% parallel beta-strand, 17% turn and 31% random-coil structure. Folate binding to FBP results in significant changes in the c.d. spectrum. Analysis of the spectrum shows a 10% decrease in antiparallel beta-strand as a result of ligand binding. Folate binding also leads to strong quenching of FBP tryptophan fluorescence. The magnitude of the quench is proportional to ligand binding. The guanidinium chloride-induced unfolding of FBP is shown to be a multistate process. Detection by c.d. and fluorescence spectroscopy lead to non-identical transitions. Modelling studies are consistent with the existence of a stable folding intermediate. Ligand binding to FBP increases the apparent folding stability of the molecule. Simultaneous detection by c.d. and fluorescence indicate that the apparent increased folding stability is derived from ligand-induced aggregation of FBP.

Animals↗
PubMed1984

[The effect of fatigue on the biopotential of muscle fiber cells].

Muscular fatigue is a biological situation which is very difficult to quantify. The Authors studied through a computer analysis the power spectrum of electromyogram, recorded from abductor digiti minimi muscle during maximal and minimal contraction effort before and after fatigue and after muscle prolonged relaxation in 8 normal subjects. No significant spectrum differences were found between maximal and minimal effort in each trial, and between the spectra obtained before fatigue and after muscle prolonged relaxation. On the contrary significant differences were found between the spectra obtained after fatigue and the other conditions. The power spectrum analysis appears, also, to be a reliable neurophysiological parameter for the study of biological aspects of muscular fatigue.

Adult↗
PubMed1989

Spectral composition of synchronized discharge of phrenic nerve activity in the rabbit and effects of pulmonary afferents.

In anaesthetized rabbits synchronization of efferent phrenic nerve discharge activity (PNA) was investigated by spectrum analysis. During hypercapnia (6-8% end-tidal CO2) in almost all animals the spectrum analysis of PNA during inspiration revealed a bimodal distribution. A broad peak was present at 45.9 +/- 7.7 Hz (MFO peak) whereas a usually well-defined peak with smaller band width was located at 100.3 +/- 17.1 Hz (HFO peak). Increase of hypercapnia promoted the peak amplitude of HFO but had no consistent effect on the amplitude of MFO. Synchronization in the HFO band gradually increased with the progress of inspiration but declined during the last third of inspiration. HFO could be demonstrated to be also present in postinspiratory activity. The amplitude of MFO slowly increased during inspiration becoming strongest at the end of inspiration. The effect of afferent inputs from pulmonary stretch receptors on synchronization of PNA was found to be very weak. Neither withholding inflation during inspiration nor bilateral vagotomy produced substantial changes of MFO and HFO. Tracheal occlusions, however, during inspiration resulted in a slight increase of the power of MFO and HFO, which mainly was due to an overall increase of power. Augmented breaths resulted in a strong shift of the HFO peak to higher frequencies which was accompanied by a dramatic increase of the peak amplitude and a decrease of the peak band width. The presumptive role of the different types of phrenic motoneurons conveying HFO is addressed.

Animals↗
PubMed2005

SH radical: the key intermediate in sulfur transformation during thermal processing of coal.

To uncouple the complex behavior of sulfur transformation during thermal processing of coal and to elucidate the main mechanism, typical organic and inorganic sulfur compounds impregnated on or mixed with a low-ash char are studied through temperature-programmed decomposition coupled with online mass spectrum analysis (TPDMS) and followed by temperature-programmed oxidation coupled also with online mass spectrum analysis (TPOMS) in a temperature range of up to 800 degrees C. It is evident that the cleavages of Cal-S and Car-S bonds, where the subscripts al and ar stand for aliphatic and aromatic carbon, respectively, in the organic compounds result in the formation of SH radicals, which then undergo secondary reactions with the char to form various sulfur compounds such as H2S, SO2, COS, and elemental sulfur, as well as sulfur structures in the char. H2 has the ability to stabilize the -* SH radicals and weaken the interactions between the -* SH radicals and the char. For the sulfur compounds, which do not generate the *SH radical, the only sulfur products detected are those formed directly from the decomposition of the starting sulfur compounds, H2S from FeS2 in H2 or SO2 from Fe2(SO4)3 in He, for example, and no sulfur structure is formed in the char. Minerals have significant effects on the bond cleavage temperature and the reactions of the *SH radicals with the char. It is clear that the *SH radical is a key species interacting with the char to form secondary sulfur compounds, while H2S and SO2 play no role in the sulfur transformation to the carbon structure.

Carbon↗
PubMed1995

Power spectral analysis of heart period variability in hypertensive patients with left ventricular hypertrophy.

This study aimed to characterize sympathovagal balance by heart period power spectrum analysis in hypertensive patients with echocardiographic evidence of left ventricular hypertrophy. Twenty ambulatory patients (11 men and 9 women), aged 50 +/- 10 years, with established essential hypertension and echocardiographic left ventricular hypertrophy, performed 24-h blood pressure monitoring and electrocardiogram Holter recording on 2 consecutive days. Twenty age- and sex-matched normal subjects comprised the control group. Power spectrum analysis, performed using the fast Fourier transform algorithm, demonstrated lower values of low and high frequency power in hypertensives than in controls, while ultralow and very low frequency power were similar in the two groups. Very low frequency, low frequency, and high frequency power increased during the night in both groups, showing a similar circadian pattern. We found a direct correlation between daytime systolic (r = 0.51; P < .05) and diastolic (r = 0.52; P < .05) blood pressure and left ventricular mass index. Moreover, negative correlations were found between left ventricular mass index and low frequency (r = -0.47; P < .05) and high frequency power (r = -0.47; P < .05). There was a direct correlation between nighttime decrease in systolic blood pressure and nighttime increase in high frequency power (r = 0.45; P < .05). As 24-h low frequency and high frequency power, obtained using the Fourier transform algorithm, both reflect the parasympathetic modulation of heart rate, our results demonstrate that hypertensive patients with left ventricular hypertrophy are characterized by a sympathovagal imbalance with a reduction of vagal tone that is more evident with increasing severity of hypertension.

Blood Pressure↗
PubMed1985

A new method for analyzing high-resolution spectra from whole-body counter in-vivo measurements.

A new method has been developed at the Pacific Northwest Laboratory to analyze pulse-height energy spectra from whole-body counter in-vivo examinations that use high-resolution Ge detectors. A simple data transformation and smoothing function is used to calculate background and identify photopeaks for isotopic analysis. This technique is beneficial for routine in-vivo measurement programs because it avoids dependence upon complex spectrum deconvolution, stripping, or other least-squares fitting techniques that complicate the assessment of measurement reliability. An in-vivo measurement spectrum is analyzed by first applying the variance stabilizing transformation to the data in each channel, which results in a variable with unit variance. A background spectrum is then determined by smoothing the transformed data. Finally, peaks are identified whenever the difference between the background spectrum and the transformed measurement spectrum exceeds 2.57 standard deviations. This method of spectrum analysis is especially suited to whole-body counting because background spectra are calculated as an integral part of the analysis procedure. This new technique has been applied successfully to routine in-vivo measurements of Pu, Am, and U. The computations for this new pulse height-energy spectrum analysis procedure are easily programmed on a desk-top or analyzer-based computer. The simplicity of the computational technique is also attractive because of the ease with which results can be verified.

Humans↗
PubMed1996

Characteristics of renal sympathetic nerve activity in sodium-retaining disorders.

Characteristics of renal sympathetic nerve activity in conscious rats with established congestive heart failure, cirrhosis, or nephrotic syndrome were analyzed using three methods: mean integrated voltage over time, power spectrum analysis, and sympathetic peak detection analysis. Compared with control rats, all three disease models had increased mean integrated voltage. On power spectrum analysis, all three disease models had increased relative power at the heart rate frequency, indicating that it was related to renal sympathetic nerve discharge coupled to the cardiac cycle. Congestive heart failure and nephrotic syndrome rats showed increased relative power in the low-frequency range, whereas cirrhotic and nephrotic syndrome rats showed decreased relative power in the high-frequency range. On sympathetic peak detection analysis, the frequency of sympathetic peaks was greater in the three disease models compared with the control rats. In cirrhotic rats, the distribution of sympathetic peak heights was shifted toward an increased number of peaks of lesser height. It is concluded that basal renal sympathetic nerve activity is chronically increased in these disease models. This is manifest as increased power coupled to the cardiac cycle, which may reflect the disease-specific defects in arterial and cardiac baroreflex control. In cirrhosis, there is possible selective activation of a subgroup of renal sympathetic nerve fibers.

Animals↗