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PubMed1989

[Power spectral analysis of heart rate and peripheral blood flow variations during total spinal anesthesia].

We evaluated the effect of total spinal anesthesia (TSA) on the heart rate and peripheral blood flow variations to evaluate if TSA could influence these parameters as indicators of autonomic nervous function (ANF). Four patients with intractable pain were treated by TSA by administration of local anesthetics (lidocaine or mepivacaine) into the C7-Th1 vertebral interspace. Power spectrum of heart rate before TSA showed three peaks; low (LO-FR, 0.04-0.095 Hz), mid (MID-FR, 0.095-0.15Hz) and high frequency areas (HI-FR, 0.15-0.3Hz). Spectral peaks of LO-FR and MID-FR disappeared during TSA (P less than 0.001). HI-FR area decreased to 3.3% of the control level (P less than 0.001). Mean peripheral blood flow was changed to 59.9% of the control level (not significant). However, peripheral blood flow variations of LO-FR decreased to 11.3% of the control level (P less than 0.001) after TSA. Furthermore, the vagal discharge disappeared promptly after TSA in dog. These results suggest that TSA depresses the vagal activity as well as the sympathetic activity innervating the cardiovascular system and therefore, heart rate and peripheral blood flow variations are totally eliminated. Thus, we conclude that heart rate and peripheral blood flow variations can serve as valid markers of ANF activity.

Anesthesia, Spinal↗
PubMed2000

Effects of one-lung ventilation on cardiac autonomic nervous activity as evaluated by power spectral analysis of heart rate variability.

The purpose of this prospective study was to evaluate the effects of one-lung ventilation on the activity of the cardiac autonomic nervous system. Ten adult patients who underwent thoracotomy were endotracheally intubated with a double-lumen tube under general anesthesia using isoflurane. After induction of anesthesia, a continuous, 256-sec electrocardiogram (ECG) was obtained during bilateral lung ventilation (control) followed by recordings during one-lung ventilation of each side. Using the R-R interval tachograms obtained for the 256-sec ECGs, low frequency (LF: 0.04-0.15 Hz) and high frequency (HF: 0.15-0.40 Hz) bands of the spectral density of the heart rate variability and the HF/LF ratio were analyzed using the fast Fourier transform algorithm. Log(HF), which indicates parasympathetic activity, increased during one-lung ventilation on each side, but did not differ between ventilated sides. Log(LF), which represents sympathetic and parasympathetic activity, increased similarly to log(HF) on both sides. Log(HF/LF), the balance of the sympathetic and parasympathetic activity, did not change during one-lung ventilation. We suggest that one-lung ventilation alone does not substantially affect the cardiac autonomic nervous system.

Adult↗
PubMed1990

Spectral analysis of heart rate variability during constant and pseudorandom exercise.

The purpose of this study was to investigate the limitation for applying a linear model to the cardiorespiratory control system. Four subjects performed the two types of exercise bouts, constant (CONST) and pseudorandom (PRBS) exercise, on an electrically braked cycle ergometer at three different work rates. The target work rate of CONST were set to 80, 100, 120% of the individual anaerobic threshold (AT). In PRBS, the work rates were varied between +/- 10% of the individual AT around the respective target work rates of CONST. Although the spectral density of beat-to-beat heart rate fluctuations showed the conventional patterns for most cases, there was no obvious difference between CONST and PRBS. These results indicated that the variation of +/- 10% of AT did not affect the heart rate variation as the output response, suggesting a dilemma inevitable to apply a linear model based on the transfer function.

Adult↗
PubMed1990

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs. Part 1. Modelling the heart/thorax acoustic system.

A system model based on the simultaneous recording and analysis of the intracardiac and thoracic phonocardiograms to estimate the time-varying properties of the heart/thorax acoustic system of the dog is described. The presence of instrumental noise in the recording of intracardiac phonocardiograms is characterised, and it is demonstrated that its effect on the estimate of the transfer and coherence functions of the system can be quantified and corrected. Application of the model to study the spectral characteristics and the acoustic transmission properties of the mitral component M1 of the first heart sound and of the aortic component A2 of the second heart sound in the dog shows that the heart/thorax acoustic system acts like a bandpass filter having a higher attenuation for A2 than for M1. Between 20 and 100 Hz, the mean attenuation of M1 is 30 dB while that of A2 is 46 dB. Above 100 Hz, the attenuation slope is -12 dB per octave for M1 and -6 dB per octave for A2.

Animals↗
PubMed2005

Electroencephalogram monitoring during anesthesia with propofol and alfentanil: the impact of second order spectral analysis.

Bispectral analysis of the electroencephalogram (EEG) has been used for monitoring anesthesia. The estimation of bicoherence allows us to determine whether a given time series represents a linear random process in cases where the bicoherence is trivial, i.e., a mere constant independent of frequency. In this study, we investigated the proportion of EEG epochs with nontrivial bicoherence during surgical anesthesia with propofol and alfentanil as an indicator for the degree of nonlinearity in the EEG. We reanalyzed 90 h of EEG recorded from 20 patients undergoing abdominal surgery using the Hinich procedure, which provides a statistical test for the following hypothesis: the EEG is a linear random process. In approximately 90% of all artifact-free, stationary EEG epochs, the bicoherence was found to be zero or a mere constant. Under these conditions, the EEG can be considered as a linear random process. Our findings suggest that the spectral information in the frequency domain delivered by the EEG monitoring during anesthesia is largely contained in the power spectrum of the signal. This calls into question the benefit of EEG bispectral analysis for monitoring anesthesia effect.

Adult↗
PubMed1994

[The spectral analysis of the P wave in patients with paroxysmal atrial fibrillation].

INTRODUCTION AND OBJECTIVE: The aim of this study is to establish if patients with paroxysmal atrial fibrillation have an abnormal spectrum of the P wave. PATIENTS AND METHODS: Thirty-five patients with previous documented atrial fibrillation were compared with a control group of 29 patients. A signal-averaged ECG was performed using an ART-1200-EPX system, and a segment covering the last 75 ms of the P wave and the next 25 mg was analyzed in each of three orthogonal leads (X, Y, Z) and in a combined one (C). The area under the spectral curve between 20 and 50 Hz was divided by the area between 0 and 20 Hz (x 100 = AR50). RESULTS: Patients with paroxysmal atrial fibrillation had greater AR50 on leads Y (78.3 +/- 42.9 vs 54.4 +/- 14.8; p < 0.01) and C (82.2 +/- 52.1 vs 58.4 +/- 14.6, p < 0.05) when compared with the control group. In the subset of patients without structural heart disease AR50 in lead X was greater. The criterion "AR50 > 55 in lead Y" identified paroxysmal atrial fibrillation with a sensitivity of 77.1% and a specificity of 85%. CONCLUSIONS: This method may be useful to detect patients at risk for paroxysmal atrial fibrillation.

Aged↗
PubMed2003

Organotypic raft cultures as an effective in vitro tool for understanding Raman spectral analysis of tissue.

There is a growing body of evidence showing that optical spectroscopy has the potential to be a useful in vivo diagnostic tool. Yet, so far there is no definitive cellular and biochemical understanding for the differences seen in the spectra from different tissue categories and disease states. In this study, we examine the use of organotypic raft cultures as an in vitro model of in vivo tissue conditions in an attempt to overcome some of the limitations of previously used methods. Organotypic raft cultures resembling normal and dysplastic epithelial cervical tissue were constructed and grown at an air-liquid interface for 2 weeks. Raman spectra of normal as well as dysplastic raft cultures were measured and compared with in vivo spectra from the corresponding tissue type. Histologic comparisons ensured that the raft cultures had similar structure and morphology to the corresponding intact tissue types. Raman spectra were also acquired from different layers of tissue. Spectral comparisons show that the Raman spectra of the raft cultures are similar to the spectra acquired from the cervix in vivo for both normal and dysplastic tissues. These results show that organotypic raft cultures are an effective and useful tool for the cellular and biochemical analysis of tissue spectroscopy.

Cell Line↗
PubMed2002

[Application of AOTF in spectral analysis. 1. Hardware and software designs for the self-constructed visible AOTF spectrophotometer].

A self-constructed visible spectrophotometer using an acousto-optic tunable filter(AOTF) as a dispersing element is described. Two different AOTFs (one from The Institute for Silicate (Shanghai, China) and the other from Brimrose(USA)) are tested. The software written with visual C++ and operated on a Window98 platform is an applied program with dual database and multi-windows. Four independent windows, namely scanning, quantitative, calibration and result are incorporated. The Fourier self-deconvolution algorithm is also incorporated to improve the spectral resolution. The wavelengths are calibrated using the polynomial curve fitting method. The spectra and calibration curves of soluble aniline blue and phenol red are presented to show the feasibility of the constructed spectrophotometer.

Acoustics↗
PubMed1998

Spectral analysis and catalytic activities of the microsomal mixed-function oxidase system of the sea anemone (phylum: Cnidaria).

Cnidarians are primarily marine organisms with a wide and diverse habitat worldwide. Previous studies from our laboratory demonstrated the presence of proteins in the molecular mass range of 50-60 KDa that were recognized by several antibodies raised against fish cytochromes P450 of the CYP 1, 2, and 3 families in microsomes prepared from the columnar regions of 5 species of sea anemones (Heffernan et al. Mar Environ Res 1996;42:353-357). Pursuant to those studies we report herein results of spectral analyses, NAD(P)H-oxidoreductase and ethoxyresorufin O-dealkylase (EROD) of sea anemone microsomal fractions. The predominant feature in the difference spectrum of dithionite (DTN)-reduced, CO-liganded anemone microsomes was a peak with lambda max of approximately 418 nm, which slowly increased for about 20 min and decreased after about 40 min. A relatively lower amplitude 450 nm peak was attained within 5 min of CO addition and was stable for up to 90 min. The 450 nm peak did not increase concomitant to the decrease in the 418 nm peak suggesting that the latter is not denatured P450. A significantly larger 450 nm peak was attained in CO-difference spectra when DTN was added prior to CO. NADPH-dependent cytochrome c (P450) reductase of the sea anemones was 1.8-3.9 nmol/min/mg protein, which is at the lower end of the range observed in invertebrates. NADH-cytochrome c reductase was 9-25 nmol/min/mg protein, while the NADH-ferricyanide (b5) reductase ranged from 73-232 nmol/min/mg protein. When microsomal EROD activity was measured under conditions in which the reaction was linear with respect to protein concentration, a decrease in fluorescence was typically observed for the initial 15 min of the time course and then increased linearly for up to 90 min; initial velocities were determined from the increasing linear region. NADPH was the preferred cofactor for EROD activity and the NAD(P)H-EROD activity was higher in Anthopleura elegantissima than Anthopleura xanthogrammica. The Bunodosoma cavernata NADPH-EROD activity was barely noted at the detection limit of the assay and NADH-EROD activity was not detected. These results are consistent with a functional P450-dependent MFO system in cnidarians, with characteristics both similar to and unique from other marine invertebrates.

Animals↗
PubMed2002

Effects of the anticholinesterase edrophonium on spectral analysis of heart rate and blood pressure variability in humans.

Edrophonium, an anticholinesterase, exerts a biphasic effect on cardiovascular autonomic drive in humans (lower doses enhance; higher doses reduce). Twenty-five anesthetized, mechanically respired (10 breaths. min(-1), constant tidal volume) patients were given either saline (n = 10) or edrophonium (0.01-1.0 mg. kg(-1), n = 15) following surgery. ECG, radial arterial pressure, and respiratory rate were sampled at 250 Hz to obtain time series for consecutive R-R intervals (RRIs), and systolic (SBP) and diastolic blood pressure (DBP). A Wigner distribution was used for time frequency mapping of spectral powers at high (HFP, 0.15-0.5 Hz) and low (LFP, 0.0-0.05 Hz) frequency. Edrophonium produced a dose-dependent decrease in heart rate [baseline 66.8 +/- 1.9 (S.E.M.) beats per minute; maximum decrease to 55.8 +/- 1.4 beats per minute with 1.0 mg. kg(-1), P < 0.01]. HFP of the RRI increased at low doses (0.2-0.4 mg. kg(-1); maximum increase to 111.0 +/- 58.2% baseline; P < 0.01) but decreased (-49.5 +/- 35.5% baseline; P < 0.01) at higher (1.0 mg. kg(-1)) doses. Edrophonium had no effect on SBP and DBP. HFP of SBP decreased with increasing doses (maximal decrease to -26.2 +/- 7.5% baseline, P < 0.01, 1.0 mg. kg(-1)). LFP of SBP was also decreased (-46.3 +/- 10.9% baseline, P < 0.01, 1.0 mg. kg(-1)). Edrophonium may enhance (lower dose) or reduce (higher dose) cardiovascular autonomic drive in humans, as evidenced by the significant changes it evokes in HFP of the RRI (parasympathetic drive), and in the HFP and LFP of SBP (sympathetic drive). These observations may account for the modest autonomic side effects of edrophonium when this drug is used clinically.

Adult↗
PubMed1987

[Waveform caused by raised intracranial pressure--application of spectral analysis in the study of waveform].

Changes in spectrum of the intracranial pressure (ICP) pulse wave were studied while ICP was raised by the epidural balloon inflation. ICP and systemic blood pressure were estimated in the lateral ventricle and thoracic aorta, respectively. Transmission of pulsation from arterial pressure to ICP was estimated by the amplitude transfer function (TFa). Waveform of ICP pulse was also evaluated by distortion factor to represent how ICP pulse is different form a pure sine wave. The spectra of ICP and arterial pressure showed basically the same pattern; they consisted of fundamental wave (FW) and three harmonic waves (HW 2, HW 3, HW 4). Amplitude and values of TFa of each spectral component were increased as ICP was raised and revealed significant correlation. FW and HW 2 components showed break points when ICP was raised up to 35 mmHg, thereafter increments of amplitude and TFa became more remarkable in the range of higher ICP. TFa and amplitude of each spectral component of ICP pulse revealed significant correlation. These findings proved that changes of ICP pulse were the results of changed efficiency of pulse transmission from arterial pressure to CSF. It was already reported that the cerebrovascular tonus had decisive influences on the transmission of pulsation from arterial pressure to ICP because lowered vascular tonus would diminish the damping effect by arterial wall and facilitate the transmission of arterial pressure pulse to ICP. The break point of amplitude and TFa were considered to indicate that tonus of cerebral artery was remarkably lowered and the autoregulation of cerebral blood flow was exhausted.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Protonation dynamics of the alpha-toxin ion channel from spectral analysis of pH-dependent current fluctuations.

To probe protonation dynamics inside the fully open alpha-toxin ion channel, we measured the pH-dependent fluctuations in its current. In the presence of 1 M NaCl dissolved in H2O and positive applied potentials (from the side of protein addition), the low frequency noise exhibited a single well defined peak between pH 4.5 and 7.5. A simple model in which the current is assumed to change by equal amounts upon the reversible protonation of each of N identical ionizable residues inside the channel describes the data well. These results, and the frequency dependence of the spectral density at higher frequencies, allow us to evaluate the effective pK = 5.5, as well as the rate constants for the reversible protonation reactions: kon = 8 x 10(9) M-1 s-1 and koff = 2.5 x 10(4) s-1. The estimate of kon is only slightly less than the diffusion-limited values measured by others for protonation reactions for free carboxyl or imidazole residues. Substitution of H2O by D2O caused a 3.8-fold decrease in the dissociation rate constant and shifted the pK to 6.0. The decrease in the ionization rate constants caused by H2O/D2O substitution permitted the reliable measurement of the characteristic relaxation time over a wide range of D+ concentrations and voltages. The dependence of the relaxation time on D+ concentration strongly supports the first order reaction model. The voltage dependence of the low frequency spectral density suggests that the protonation dynamics are virtually insensitive to the applied potential while the rate-limiting barriers for NaCl transport are voltage dependent. The number of ionizable residues deduced from experiments in H2O (N = 4.2) and D2O (N = 4.1) is in good agreement.

Binding Sites↗
PubMed2001

Neonatal magnetoencephalography and spectral analysis.

PURPOSE: We performed a prospective study of neonatal brain function on 44 respective term neonates who were delivered normally, without any clinical signs of brain damage. Thirty were associated with a normal pregnancy and labor with normal values of Apgar scores, umbilical cord pH and birth weight, while 14 neonates were the result of pre-eclamptic pregnancy. METHODS-RESULTS: Biomagnetic measurements were performed by means of a Superconducting Quantum Interference Device (SQUID) in an electrically shielded room of low magnetic noise. Biomagnetic signals (waveforms) recorded from neonatal brains in the frequency range of 2-7 Hz were expressed in terms of magnetic power spectral amplitudes. These were low (mean value 163.2, SD 22.57) in almost all neonates from the "normal pregnancy" group, while they were high (mean value 211.6, SD 37.74) in most neonates from the "pre-eclamptic" group. The difference between the two groups was statistically significant (Student's t-test, p < 0.005). CONCLUSION: A statistically significant difference in spectral amplitudes of neonatal brain activity was observed between normal term neonates and the pre-eclamptic neonates. Biomagnetic measurements of neonatal brain activity could provide clinical practice with a promising procedure for assessing brain function.

Adolescent↗
PubMed1989

Ultrasonography versus amniotic fluid spectral analysis: are they sensitive enough to predict neonatal complications associated with isoimmunization?

The modern management of pregnancy complicated by erythroblastosis fetalis is based on serial amniocenteses followed by either intrauterine transfusions or early delivery of affected infants, depending on the gestational age. A retrospective study was undertaken involving 92 isoimmunized pregnancies in which ultrasonography and amniotic fluid analyses were used to assess the relative predictive values for neonatal complications. Our data demonstrated that ultrasonography and optical density analyses were comparable in the evaluation of the isoimmunized pregnancy. The combined information from both these modalities did not increase the predictive value over that observed with either one alone. Both instruments were found to have high negative predictive values. However, neither method, used singly or in combination, was highly predictive of neonatal complications. In light of the low positive predictive values, caution should be exercised in using the results of amniotic fluid spectral analyses and/or ultrasound examinations for predicting perinatal complications.

Amniotic Fluid↗
PubMed1991

Spectral analysis criteria in duplex scanning of aortoiliac and femoropopliteal arterial disease.

To validate the use of duplex scanning in the detection of lesions in the aortoiliac and femoropopliteal arteries, duplex scanning was prospectively compared to intra-arterial digital subtraction angiography in 61 patients with peripheral atherosclerotic disease. Based on a peak systolic velocity ratio greater than or equal to 2.5 or the absence of a Doppler signal, the overall sensitivity and specificity to detect lesions of greater than or equal to 50% diameter reduction was 84% and 96%, although some segments in the femoropopliteal arteries showed a sensitivity of only 60%-70%. Occlusions were detected with an overall sensitivity of 92% and specificity of 99%. The existence of a bi/triphasic Doppler signal, a window in the systolic spectral waveform and an end diastolic velocity greater than or equal to 60 cm/s has additional value in further grading of stenoses. This study shows that duplex scanning is highly comparable to angiography in the detection greater than or equal to 50% diameter reducing lesions in the aortoiliac arteries. Further evaluation is needed for the femoropopliteal arteries.

Angiography, Digital Subtraction↗
PubMed1994

Power spectral analysis of blood pressure fluctuations during sleep in normal and decerebrate cats.

Arterial blood pressure fluctuations during sleep were investigated with power analysis technique in both normal and decerebrate cats. In the initial postoperative stage lasting about 3 to 4 days, intact cats displayed, during paradoxical sleep, phasic increases in arterial blood pressure which were superimposed on a tonic hypotension. In the later chronic stage, however, the animals showed the phasic hypertension being superimposed on the background of a tonic hypertension. Regardless of these stages, the blood pressure during paradoxical sleep exhibited a 1/f-like spectrum, expressed by the power spectral density which is inversely proportional to the Fourier frequency f. On the other hand, a power spectral profile of the blood pressure during slow wave sleep presented a white noise-like pattern within the same frequency range of 0.1-0.01 Hz. After brainstem transections at the pontomesencephalic border, the cats exhibited consistently a sustained fall in blood pressure during paradoxical sleep and the power spectral density of the blood pressure displayed a white noise-like pattern throughout the survival periods of one month or more. These observations indicate that the blood pressure fluctuations in the 1/f spectrum during paradoxical sleep originate in rostral brain structures.

Animals↗
PubMed1999

Spectral analysis of heart rate variability in elderly non-dipper hypertensive patients.

To assess by autoregressive model the frequency domain heart rate variability (HRV) during clinostatism and after passive orthostatic load (head-up tilt), 81 hypertensive and normotensive subjects (42 men and 39 women) were subdivided into four groups: 20 adult normotensive subjects (Group 1); 21 elderly normotensive subjects (Group 2); 20 elderly hypertensive subjects with nocturnal blood pressure (BP) falls (Group 3); and 20 elderly hypertensive subjects without nocturnal BP falls (Group 4). They were chosen to assess the influence of aging and arterial hypertension on sympathetic-parasympathetic balance. The age-related decrease observed in nearly all HRV spectral frequency components (normalised units [NUs], high frequency [HF] and low frequency [LF]) was reported in elderly patients in rest conditions. LF indexes resulted in decreases in Group 3 and these data seemed to be emphasised in Group 4. After passive tilt, spectral data were recorded as follows: 25.3+/-1.8 vs 17.8+/-2.2 HF, Group 2 vs Group 1, P<0.001; 72.5+/-0.8 vs 75.6+/-1.8 LF, P< 0.001, Group 2 vs Group 1. Both sympathetic and parasympathetic indexes were lower in Group 3 (44.6+/-1.1 vs 72.5+/-0.8 LF, P< 0.001, Group 3 vs Group 2; 9.9+/-1.8 vs 25.3+/-1.8 HF, P < 0.001, Group 3 vs Group 2) and data became clearer in Group 4 (8.5 2.1 vs 9.9+/-1.8 HF, P< 0.001; 40.4+/-1.5 vs 44.6+/-1.1 LF, Group 4 vs Group 3). The established influence of aging on autonomic nervous system activity appears to be increased by arterial hypertension due to worsening of the sympathetic-parasympathetic response to standardised stimulation. The loss of nocturnal BP declines in arterial hypertension was found to occur in association with a decrease in autonomic nervous system activity.

Adult↗
PubMed1982

Objective criteria for the interpretation of carotid artery spectral analysis patterns.

The duplex scanner (imager + pulsed Doppler) in combination with a fast Fourier transform spectrum analyzer has been used to identify areas of arterial narrowing. To evaluate its effectiveness in the detection of clinically significant carotid stenosis, 1 previously described and 2 original objective parameters were applied to the real time sound frequency tracings from 157 carotid arteries that also had angiograms available to determine the presence and degree of stenotic involvement. There was a statistically significant difference between the means of the test scores of the group of vessels with high grade narrowing (greater than or equal to 60%) and those with less than 40% stenosis for all 3 criteria. Of major clinical interest were our 2 parameters, the 3-point diastolic internal carotid frequency total and the internal-to-common carotid spectral area ratio, both of which showed considerable promise as predictors of stenotic disease. For each test, 40/46 (87%) of the test scores of the arteries with 50% or greater narrowing fell outside 2 standard deviations (95% confidence level) of the means of the vessels with less than 50% stenosis. A previously reported parameter, the internal-to-common carotid peak systolic frequency ratio, was notably less discriminant in this regard.

Arterial Occlusive Diseases↗