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PubMed1993

Power spectrum analysis and heart rate variability in Stage 4 and REM sleep: evidence for state-specific changes in autonomic dominance.

The present study investigated autonomic activity during NREM and REM sleep stages and wakefulness by spectral analysis of heart rate variability. The results demonstrated that NREM sleep in humans was characterized by a widely different autonomic activation pattern than REM sleep: high parasympathetic activity was found in NREM, while REM was characterized by attenuated vagal tone, and augmented sympathetic activity. The overall pattern during wakefulness showed an intermediate position between NREM and REM patterns; parasympathetic activity was lower than in NREM and higher than in REM, with an opposite trend for sympathetic activity.

Journal Article↗
PubMed1996

Power spectrum analysis contribution to the detection of cardiovascular dysautonomia in multiple sclerosis.

In multiple sclerosis (MS) autonomic cardiovascular dysfunction is an uncommon, but potentially dangerous event, to which studies of spectral analysis of heart rate variability have not been applied, yet. MATERIAL AND METHODS--We studied 16 patients with definite MS (11 women and 5 men, mean age 30.3 +/- 7.4 yrs., mean EDSS 2.06 +/- 1.42) and 16 sex- and age-matched healthy controls. Besides cardiovascular reflex tests (valsalva manoeuvre, deep breathing, lying to standing, Blood Pressure response to standing and sustained handgrip), each underwent spectral analysis of the R-R interval short-term variability at rest and after tilting, to detect three components: very low frequency (VLF), low frequency (LF) and high frequency (HF). A recent brain MRI was obtained from patients, to compare plaque characteristics with spectral parameters. RESULTS--At cardiovascular reflexes, only four patients (25%) showed an impairment, mostly of a mild degree. VLF and LF at rest were lower in MS subjects than in controls (p < 0.01). No significant correlation was found between spectral parameters and lesion area or localization as detected on MRI. CONCLUSIONS--Spectral analysis could usefully flank reflex tests to detect autonomic subclinical cardiovascular abnormalities.

Adult↗
PubMed1996

Pulse spectrum analysis of chemical factory workers with abnormal blood test.

Double blind tests to check the correlation between pulse diagnosis and liver function tests were performed. Blood tests including T-Bil, D-Bil, SGOT and SGPT of 70 chemical factory workers were compared with pulse analysis. Special attention was paid to the indicators of liver and lung meridians for pulse diagnosis. It was found that using the criterion (1) C1 > or = 3+ and C1 + C4 > or = 4+ (hyperfunction) and (2) C1 < or = 3-(hypofunction) as abnormal liver meridian (for C1, every 5% above normal give one +, every 5% below normal give one-; for C4 every 10% above normal give one +, every 10% below normal give one -). The correlation or agreement between the blood tests and the pulse diagnosis was very high (noncorrelation chance checked by X2-test, P < 0.001, degree of agreement checked by Kappa test Ka = 0.61 which means a substantial relationship). Suggestions such as more tests, more criteria and precautions for future study are also proposed.

Adult↗
PubMed1996

Pulse spectrum analysis of hospital patients with possible liver problems.

Pulse diagnosis were performed on 85 patients who came to the hospital for liver and gall-bladder problems. Correlation between liver tests, which include T-Bil, D-Bil, SGOT, SGPT, ZTT, Alp, gamma-GT, Cho, Alb, and ultra sound scanning, and pulse diagnosis were analyzed. 77 out of 85 subjects showed abnormal liver tests. We used the following 5 criteria for pulse diagnosis as liver abnormality to test the correlation: (1) C1 > or = 3+ and C1 + C4 > or = 4+ or C1 + C6 > or = 4 (in intensity); (2) C1 < or = 3 (in intensity); (3) C6 > or = 3 and C1 + C6 > or = 4 (in intensity); (4) C6 < or = -2 (in intensity) and C6 < or = -2 (in the phase) and (5) C1 > or = 2 C3 < or = -2 (in intensity) or C3 < or = -2 (in the phase). For C1 (liver) every 5% above normal was given one "+," every 5% below normal was given one "-." For C3 (spleen), C4 (lung), C6 (gall-bladder), every 10% above normal was given one "+,", every 10% below normal was given one "-." For the phase, every 10% delay in the traveling speed was given one "-." When considering only the "+" and "-" states and neglecting the quantity of "+" and "-," there are 2(11) (from intensity) x 2(11) (from phase), which equal 2048 x 2048 possible states in the pulse analysis. We considered only 5 criteria for liver abnormality; the correlation was still very high, p < 0.0002, kappa = 0.64. It strongly suggests that meridian theory and pulse diagnosis have physiological and pathological importance.

Adolescent↗
PubMed1986

Description and validation of an ECG removal procedure for EMGdi power spectrum analysis.

We describe a cross-correlation procedure for removing contaminating electrocardiogram (ECG) complexes from the diaphragmatic electromyogram (EMGdi). First, the operator selects ECG templates from the EMGdi signal during expiratory intervals. Second, these templates are used to locate ECG complexes occurring during inspiratory EMGdi activity. Third, at the point of maximum correlation between the template and these ECG complexes, the template is adjusted in size and offset to "match" the ECG complex, and adjustments are determined by the linear regression coefficients. Finally, the modified template is subtracted from the EMGdi signal. To evaluate our method, we compared the power spectral density (PSD) obtained from processing EMGdi signals by our method with those obtained from the EMGdi signal in which ECG complexes had been removed by gating. Our results indicate that PSD obtained by these two different methods shows no statistically significant differences with respect to the following features: centroid frequency, median frequency, total power, standard deviation, skewness, and kurtosis.

Analysis of Variance↗
PubMed1989

Power spectrum analysis of heart rate variability in human cardiac transplant recipients.

Beat-to-beat heart rate variability was studied by power spectral analysis in 17 orthotopic cardiac transplant patients. Heart rate power spectra were calculated from eighty-four 256-second recordings and compared with those taken from six normal subjects. The power spectra from the control subjects resolved into discrete peaks at 0.04-0.12 Hz and 0.2-0.3 Hz, whereas those of heart transplant recipients resembled broad-band noise without peaks. Log total power in the 0.02-1.0 Hz range was greater in the control subjects (0.982 +/- 0.084 [0.206], mean +/- SEM [SD]) than in the transplanted subjects (-0.766 +/- 0.059 [0.541]), (p less than 0.0001). Fifty-five electrocardiographic recordings from transplant patients were done within 48 hours of an endomyocardial biopsy. When the power spectra of those patients whose endomyocardial biopsies showed evidence of myocardial rejection were compared with those from patients who were found to be free of rejection, a significant difference was found in log total power (-0.602 +/- 0.090 [0.525] vs. -0.909 +/- 0.136 [0.577], p less than 0.02). We conclude that denervation of the heart significantly reduces heart rate variability and abolishes the discrete spectral peaks seen in untransplanted control subjects and that the development of allograft rejection may significantly increase heart rate variability.

Adult↗
PubMed1994

Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt.

BACKGROUND: The powers of the low-frequency (LF) and high-frequency (HF) oscillations characterizing heart rate variability (HRV) appear to reflect, in their reciprocal relationship, changes in the state of the sympathovagal balance occurring during numerous physiological and pathophysiological conditions. However, no adequate information is available on the quantitative resolution of this methodology. METHODS AND RESULTS: We studied 22 healthy volunteers (median age, 46.5 years) who were subjected after a rest period to a series of passive head-up tilt steps randomly chosen from the following angles: 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. From the continuous ECG, after appropriate analog-to-digital conversion, a personal computer was used to compute, with an autoregressive methodology, time and frequency domain indexes of RR interval variability. Spectral and cross-spectral analysis with the simultaneously recorded respiratory signal excluded its contribution to LF. Age was significantly correlated to variance and to the absolute values in milliseconds squared of very-low-frequency (VLF), LF, and HF components. The tilt angle was correlated to both LF and HF (expressed in normalized units [nu]) and to the LF-to-HF ratio (r = .78, -.72, and .68; respectively). Lower levels of correlation were found with HF (in ms2) and RR interval. No correlation was present between tilt angle and variance, VLF, or LF (in ms2). Individual analysis confirmed that the use of nu provided the greatest consistency of results. CONCLUSIONS: Spectral analysis of HRV, using nu or LF-to-HF ratio, appears to be capable of providing a noninvasive quantitative evaluation of graded changes in the state of the sympathovagal balance.

Adult↗
PubMed1997

Instant power spectrum analysis of heart rate variability during orthostatic tilt using a time-/frequency-domain method.

BACKGROUND: Spectral analysis of heart rate (HR) variability (HRV) requires, as a rule, some level of stationarity and, as a result, is inadequate to quantify biological transients. A time-/frequency-domain method (TF) was developed to obtain an instant spectral power (SP) of HRV during tilt. METHODS AND RESULTS: HR was recorded by Holter monitoring in volunteers and analyzed with a TF, the smoothed pseudo-Wigner-Ville transformation (SPWVT), with the table inclination randomly set or continuously increased while the table rotated in head-up position. (1) The SPWVT assesses, beat by beat, the instant center frequency (ICF) of the SP. ICF correlates better with instant HR than the ratio of low- (LF) to high-frequency (HF) oscillations. The transient effect of tilt is better characterized as a shift of SP toward lower frequencies than by changes in amplitudes. (2) The method evidences variations of HR from one second to another. During the passage to head-up position, the vagal withdrawal and the sympathetic activation occur nearly simultaneously, as indicated by the instant changes in both LF and HF amplitudes and ICF. (3) The averaged results of the SPWVT give results similar to those previously obtained with autoregressive algorithms. CONCLUSIONS: The SPWVT is a new tool to explore HR transitions such as periods before episodes of arrhythmias on a time scale of one beat and allows quantification of an instant frequency index (ICF) that closely reflects the instantaneous relationship between sympathetic and vagal modulations.

Adult↗
PubMedDate not supplied

Ticlopidine in the treatment of multiple atherosclerotic arteriopathy: a strain gauge plethysmography and Döppler spectrum analysis evaluation.

The effect of ticlopidine was compared with flunarizine in patients with iliac-femoral and/or femoral-popliteal arteriosclerotic arteriopathy accompanied by lesions of the cervical arteries of no haemodynamic significance. In the lower limbs, plethysmography (strain gauge measurements) and Döppler ultrasonography integrated by spectral analysis of the cervical arteries showed qualitative and quantitative improvements of the regional haematic flow. Side-effects were negligible which suggests that ticlopidine is useful in the treatment of multiple arteriosclerotic arteriopathy.

Aged↗
PubMed1995

Fluctuations in autonomic nervous activity during sleep displayed by power spectrum analysis of heart rate variability.

OBJECTIVE: The use of an efficient noninvasive method to investigate the autonomic nervous system and cardiovascular control during sleep. BACKGROUND: Beat-to-beat heart rate variability displays two main components: a low-frequency (LF) one representing sympathetic and parasympathetic influence and a high-frequency (HF) component of parasympathetic origin. Sympathovagal balance can be defined as LF/HF ratio. METHODS/DESIGN: We reviewed normal, standardly staged all-night polysomnograms from 10 healthy children aged 6 to 17 years. Recorded 256-second traces of heart rate and respiration were sampled. Power spectra of instantaneous heart rate and respiration were computed using a fast Fourier transform method. RESULTS: The study revealed a decrease in LF during sleep, with minimal values during non-REM slow-wave sleep and elevated levels similar to those of wakefulness during REM. HF increased with sleep onset, reaching maximal values during slow-wave sleep, and behaved as a mirror image of LF. LF/HF ratio displayed changes similar to those in LF. CONCLUSION: The sympathetic predominance that characterizes wakefulness decreases during non-REM sleep, is minimal in slow-wave sleep, and surges toward mean awake levels during REM sleep. The autonomic balance is shifted toward parasympathetic predominance during slow-wave sleep. This noninvasive method used to outline autonomic activity achieves results that are in complete agreement with those obtained with direct invasive tools.

Adolescent↗
PubMed2002

Nonnegative color spectrum analysis filters from principal component analysis characteristic spectra.

Nonnegative color analysis filters are obtained by using an invertible linear transformation of characteristic spectra, which are orthogonal vectors from a principal component analysis (PCA) of a representative ensemble of color spectra. These filters maintain the optimal compression properties of the PCA scheme. Linearly constrained nonlinear programming is used to find a transformation that minimizes the noise sensitivity of the filter set. The method is illustrated by computing analysis and synthesis filters for an ensemble of measured Munsell color spectra.

Journal Article↗
PubMed2005

Local spectrum analysis of field propagation in an anisotropic medium. Part I. Time-harmonic fields.

The phase-space beam summation is a general analytical framework for local analysis and modeling of radiation from extended source distributions. In this formulation, the field is expressed as a superposition of beam propagators that emanate from all points in the source domain and in all directions. In this Part I of a two-part investigation, the theory is extended to include propagation in anisotropic medium characterized by a generic wave-number profile for time-harmonic fields; in a companion paper [J. Opt. Soc. Am. A 22, 1208 (2005)], the theory is extended to time-dependent fields. The propagation characteristics of the beam propagators in a homogeneous anisotropic medium are considered. With use of Gaussian windows for the local processing of either ordinary or extraordinary electromagnetic field distributions, the field is represented by a phase-space spectral distribution in which the propagating elements are Gaussian beams that are formulated by using Gaussian plane-wave spectral distributions over the extended source plane. By applying saddle-point asymptotics, we extract the Gaussian beam phenomenology in the anisotropic environment. The resulting field is parameterized in terms of the spatial evolution of the beam curvature, beam width, etc., which are mapped to local geometrical properties of the generic wave-number profile. The general results are applied to the special case of uniaxial crystal, and it is found that the asymptotics for the Gaussian beam propagators, as well as the physical phenomenology attached, perform remarkably well.

Journal Article↗