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PubMed1981

[Spectral analysis of frequencies by conventional Doppler effect examination of the supra-aortic trunks (author's transl)].

Using a directional Doppler (4 MHz) coupled to a frequency analyser, authors investigate the supra-aortic trunks on 90 patients documented by arteriography. The analyser is made of a 16 filter bank system giving a spectrum composed of 16 frequency bands within range of 160 Hz to 4,800 Hz. Data analysis is made on a computer using the comparison means test and the discriminant analysis. Authors compare frequencies on normal common carotid arteries between a group (N = 102) with internal and external carotid arteries free of lesions on one hand, and a group (N = 75) with stenosis or occlusion of internal and/or external carotid arteries on the other hand. They don't note any significant difference for each on of the 16 frequency bands. Comparison of frequencies between normal subclavian arteries (N = 115) and subclavian arteries with proximal stenosis or occlusion (N = 24) shows a significant difference concerning the following bands : F12, F14, F15, F16 (p = 0.05), F13 (p = 0.01). Comparison of frequencies between normal internal carotid arteries (N = 108) and stenosed internal carotid arteries (N = 57) shows significant difference concerning : F11 (p = 0.05), F7, F8, F9, F12, F13, F14, F15, F16 (p = 0.01). On the other side, the discriminant function distinguishes a normal internal carotid artery from a stenosed internal carotid artery in 90% of cases, whatever the stenosis degree is. A discriminant function, added to this analyser, could obtain a frequency analysis easier and less expensive than by fast Fourier transform.

Arterial Occlusive Diseases↗
PubMed1980

[Minimum phase model of a dynamic spectral analysis of sounds at the periphery of hearing].

The model consists of independent frequency-channels the amplitude-frequency characteristics (AFC) of which are assigned by the investigator. The phase characteristics are computed. Concrete minimum-phase model is described and illustrated. The temporal and frequency characteristics of this model are consistent with experimental data on peripheral auditory system. The AFC can be easily reformed, so the model is convenient for investigation of functional models of peripheral auditory analysis.

Computers↗
PubMedDate not supplied

[Macroscopic fluctuations--a general property of aqueous solutions of different proteins and other substances. Statistical spectral analysis of macroscopic fluctuations].

When studying enzymic activities in successively chosen portions of solutions of pyruvatekinase, hexokinase, lactatedehydrogenase, alkaline phosphatase, acetylcholinesterase and trypsin fast macroscopic fluctuations were revealed. These fluctuations were found earlier in protein preparations of the actomyosin complex and creatinkinase and described as "conformation fluctuations". Similar macroscopic fluctuations were also revealed when measuring the rate of reaction between ascorbic acid and dichlorphenolindophenol (DCAPI). The spectra of macroscopic fluctuations in solutions of different proteins and ascorbic acid+DCAPI are similar to each other in principle. This gives grounds to consider the ability towards macroscopic fluctuations to be a common property of solutions of different substances.

2,6-Dichloroindophenol↗
PubMed1994

Rapid development of nitrate tolerance in healthy volunteers: assessment using spectral analysis of short-term blood pressure and heart rate variability.

Nitrate tolerance is characterized by a loss of nitroglycerin (NTG) vasodilating and hypotensive effects during continuous administration, but is difficult to detect clinically. We hypothesized that the decrease in arterial blood pressure (BP) and the reflex sympathetic activation and tachycardia due to baroreflex deactivation associated with rapid intravenous (i.v.) infusion of NTG would be decreased during continuous NTG patch therapy as a result of tolerance to transdermal NTG. Sympathetic activation was measured as the change in amplitude of low-frequency (66-129 mHz) oscillations in BP and heart rate (HR) recorded by a noninvasive method. Eleven healthy male volunteers received rapid i.v. infusion of 0.45 mg NTG in 1 min on 3 consecutive days: before NTG patch, after 22.5 h of patch therapy, and 22.5 h after patch removal. The maximum decrease in systolic BP (SBP) and maximum reflex tachycardia as well as the sympathetic activation produced by i.v. NTG were compared during each of the three study periods. The maximum decrease in SBP was 38 +/- 8 mm Hg before NTG patch and 27 +/- 15 mm Hg during NTG patch (p < 0.05), with return to baseline values (37 +/- 13 mm Hg) after patch removal. There was no significant change in amplitude of reflex tachycardia among study periods. However, low-frequency oscillations in SBP increased by 40 +/- 31% in the absence of NTG patch and by only 9 +/- 35% after 22.5 h of patch therapy (p < 0.05). Patch removal resulted in a significant rebound increase in these oscillations (70 +/- 51%; p < 0.05 vs. baseline).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

[Detecting blood pressure variation using spectral analysis in obstructive sleep apnea syndrome with and without nCPAP therapy].

The variation of blood pressure was investigated by power spectrum analysis in 12 patients with severe sleep apnea with and without nCPAP-therapy. In the baseline findings systolic and diastolic variation consisted of mainly two types of pressure oscillations: Swings of slow frequency (0-0.06 Hz) in tight association with the periodicity of breathing disorder and arousal and extensive respiratory pressure waves (0.2-0.5 Hz) due to the increased intrathoracic pressure changes during breathing efforts with partial or complete obstruction of the upper airway. In general systolic was higher than diastolic variation and the contribution of slow pressure oscillations was considerably bigger than that of respiratory waves. Sufficient nCPAP-therapy resulted in a decrease of the mean pressure and in a clear reduction of systolic and diastolic variation in which both types of pressure waves were diminished in a similar manner. At last there was a higher proportion of pressure waves in the frequency range of the Mayer-waves (0.06-0.2 Hz) with nCPAP-therapy.

Adult↗
PubMed1993

Cardiovascular variability after clonidine challenge: assessment of dose-dependent temporal effects by means of spectral analysis.

Effects of four intravenous (i.v.) doses (0.25, 0.5, 1, and 2 micrograms/kg) of the alpha 2-adrenoceptor agonist clonidine (CLO) were studied in 7 normotensive male volunteers in a placebo-controlled double-blind randomized design to evaluate the role of alpha 2-adrenoceptors in spontaneous short-term cardiovascular fluctuations. Heart rate (HR), systolic and diastolic blood pressure (SBP, DBP; Finapres device), stroke volume (SV) and total peripheral resistance (TPR) were monitored for 1 h after infusion of CLO while the subjects rested in a semirecumbent position. For HR, SBP, and DBP, power spectra and variation coefficients were calculated for consecutive time segments of 2.5 min. Power density was assessed for three frequency bands: low (LFB, 0.02-0.06 Hz), mid (MFB, 0.07-0.14 Hz), and high (HFB, 0.15-0.40 Hz). Per time-segment, baroreflex sensitivity (BRS) was estimated as the gain (or modulus) in MFB between systolic pressure values and R-R interval times. Decreases in mean levels of SBP and DBP were observed within 15 min after infusion of > or = 0.5 micrograms/kg CLO. HR first showed a slight increase 15 min after infusion of 0.5, 1, and 2 micrograms/kg CLO, but decreased subsequently as in all doses, including placebo. SV and TPR decreased after a dose of 2 micrograms/kg CLO. LFB and MFB power of HR were reduced after 2 micrograms/kg CLO, but only during the first 30 min after infusion; during this period, respiratory depth was also diminished, indicating that these effects may reflect a reduction in sympathetic outflow as well as a reduction in vagal outflow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

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