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At least 811 records · Page 45Linked to original sources
PubMed2004

Cardiac autonomic activity in obstructive sleep apnea: time-dependent and spectral analysis of heart rate variability using 24-hour Holter electrocardiograms.

To analyze the function of cardiac autonomic regulation in patients with obstructive sleep apnea syndrome (OSAS), we enrolled 36 patients with OSAS and divided them according to the apnea hypopnea index (AHI) into 2 groups: Group I (n=19) had mild OSAS (AHI < 20) and Group II (n=17) had severe OSAS (AHI > or = 20). The findings were compared with those of 24 healthy control subjects who were matched for age, sex, blood pressure, and body mass index. All participants underwent 24-hour Holter monitoring, with continuous time-dependent and spectral analysis of heart rate variability. In addition, we performed arrhythmia analysis. Frequent or repetitive ventricular arrhythmias (> or = 30 premature ventricular beats/hour) were detected in 15 (42%) patients with OSAS and in 6 (25%) members of the control group. In both mild and severe OSAS, SDNN was significantly lower than in controls, and SDANN findings were similar. In mild OSAS, RMSSD values were not significantly lower than in controls, but in severe OSAS they were. The ULF, VLF, LF and LF/HF values of both groups of OSAS patients were significantly higher than those of controls, but their HF values were lower. The mean LF/HF ratio during the same period was significantly higher in Group II than in Group I and the control group. Our results suggest that cardiac autonomic activity may be altered in patients with OSAS throughout a 24-hour period, that this alteration occurs even in the absence of hypertension, heart failure, or other disease states, and that it is linked to the severity of OSAS.

Adult↗
PubMed2001

Quantitative electroencephalography spectral analysis and topographic mapping in a rat model of middle cerebral artery occlusion.

Electroencephalography (EEG) has a long history in clinical evaluations of cerebrovascular disease. Distinct EEG abnormalities, such as increased slow delta activity, voltage depression and epileptiform discharge, have been identified in stroke patients. However, preclinical use of EEG analysis of cerebral ischaemia is less documented. We report a new rat model of EEG topographic mapping during permanent and transient middle cerebral artery occlusion. Ten EEG electrodes were implanted on the rat skull, symmetrically covering the cortical regions of two hemispheres. Monopolar EEG recordings were acquired from each animal at multiple time points during the initial 24 h, and again once daily for 7 days. Traditional EEG examinations, quantitative EEG (qEEG) spectral analysis and topographic EEG mapping were employed for comprehensive data analyses. Several distinct spatiotemporal EEG abnormalities were identified in the ischaemic rat brain. In the ipsilateral hemisphere, pronounced increase in delta activity was observed in each recorded area within 24 h of injury. While sharp waves and spike complexes dominated the parietal region, a nearly isoelectric EEG state was seen in the temporal region. After 48 h, spontaneous, albeit incomplete, recovery of EEG activities developed in all rats. Reperfusion appeared to promote delta and alpha recovery more efficiently. The contralateral EEG changes were also recorded in two phases: an acute moderate increase in delta activities with intermittent rhythmic activities, followed by a delayed and significant increase in beta activities across the hemisphere. The similarities of rat qEEG profiles identified in this study to that of stroke patients and the application of topographic mapping broaden our research technology for preclinical experimental studies of brain injury.

Animals↗
PubMed1994

Power spectral analysis of heart rate and blood pressure variability in lumbar epidural anaesthesia.

The purpose of this study was to evaluate autonomic nervous system activity during high and low lumbar epidural anaesthesia. Ten patients undergoing lower limb surgery with lumbar epidural anaesthesia (low epidural anaesthesia group; mean upper dermal block level, T10.7 +/- 1.1), and ten patients undergoing either abdominal total hysterectomy or inguinal hernia under lumbar epidural anaesthesia (high epidural anaesthesia group; mean upper dermal block level, T5.1 +/- 1.0). Ten healthy volunteers were used as the control group. The autonomic nervous system activity was measured by heart rate and blood pressure variability with power spectral analysis. For the analysis of heart rate variability, frequency components were divided into two factors, a low frequency component RR (LFCRR: 0.03 Hz-0.15 Hz) that mediated sympathetic and parasympathetic activity and a high frequency component RR (HFCRR: 0.15 Hz-0.4 Hz) that mediated parasympathetic activity. In the analysis of blood pressure variability, the frequency components were also divided into two factors; a low frequency component of systolic blood pressure and diastolic blood pressure (LFCSBP and LFCDBP: 0.03 Hz-0.15 Hz) that was mediated by peripheral sympathetic vasomotor activity and a higher frequency component of systolic blood pressure and diastolic blood pressure (HFCSBP and HFCDBP: 0.15 Hz-0.4 Hz) that was mediated by a mechanical consequence of respiration. There were no changes in heart rate variability during epidural anaesthesia. However, LFCSBP and LFCDBP decreased in high epidural anaesthesia (P < 0.01). On the contrary, LFCSBP increased in low epidural anaesthesia (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1997

Acetyl-L-carnitine flux to lipids in cells estimated using isotopomer spectral analysis.

Acetyl-L-carnitine is known as a reservoir of activated acetyl units and as a modulator of metabolic function. The objective of this study was to quantify the fate of the acetyl moiety of acetyl-L-carnitine in lipogenic pathways. Lipogenesis was studied in an adipocyte model, differentiated 3T3-L1 cells, and a hepatoma cell, HepG2 cells. Lipogenesis and ketogenesis were examined in rat hepatocytes. Both de novo synthesis and elongation of fatty acids were investigated using gas chromatography/mass spectrometry and [1,2-(13)C]acetyl-L-carnitine. Comparisons were performed with [13C]glucose and [13C]acetate. Isotopomer Spectral Analysis, a stable isotope method for differentiating between the enrichment of the precursor and the amount of synthesis was used to analyze the data. Acetyl-L-carnitine was generally less effective than acetate as a precursor for de novo lipogenesis. The effects of acetyl-L-carnitine were not identical to those of acetate plus carnitine as expected if acetyl-L-carnitine flux to acetyl CoA is controlled by carnitine acetyl transferase. Acetyl-L-carnitine (2 mM) contributed approximately 10% of the lipogenic acetyl-CoA used for synthesis and elongation as well as 6% of the ketogenic acetyl-CoA. No differences were found between the precursor enrichment for de novo lipogenesis and for elongation of saturated fatty acids. Flux of acetyl-L-carnitine to lipid was increased, not decreased, by the ATP citrate lyase inhibitor, -hydroxycitrate. In contrast, flux of glucose to lipid was dramatically decreased by this inhibitor. These results indicate that flux of acetyl-L-carnitine to lipid can bypass citrate and utilize cytosolic acetyl-CoA synthesis.

3T3 Cells↗
PubMed2000

Assessment of the otolith-autonomic response using spectral analysis of the R-R interval and blood pressure.

The effects of otolith stimulation on systolic blood pressure (SBP) and R-R interval fluctuations were investigated in 12 healthy subjects and 5 patients with loss of labyrinthine function. The vestibular otolith organs were stimulated by centrifugal forces, the constant rotation of a chair fixed outside of the rotation axis on the horizontal plane. The chair was fixed along the direction of centrifugal force (eccentric rotation [ECR]) or along the tangent line (eccentric lateral rotation [ECLR]). The ECR stimulates both the utricular and saccular maculae, whereas the ECLR stimulates only the utricular maculae. Spectral analysis showed that in the healthy subjects, low-frequency SBP increased significantly during ECR but not during ECLR. There was no significant increase in low-frequency SBP in patients with labyrinthine loss. In the R-R interval analysis, however, the low- and high-frequency components did not change significantly in the healthy subjects during ECR. Our findings indicate that stimulation of the otolith maculae, especially the saccular organs, predominantly produces augmentation of the alpha-sympathetic activities rather than cardiac sympathovagal outflow to the heart.

Adult↗
PubMed1977

Screening for carotid junction disease by spectral analysis of Doppler signals.

The established test for disease in the internal carotid artery using continuous wave Doppler is to listen for flow velocity changes over the supraorbital artery with ipsilateral temporal (or facial) artery compression. This is only reliable when there is a reduction in mean pressure (and flow) distal to disease in the internal carotid artery, ie reduction of lumen diameter by more than 85%. In this study, 101 vessel segments (48 with disease at the carotid junction, 53 normal) were compared with the results of angiography. Seven gave a positive temporal artery occlusion test, all of which showed severe disease. However, spectral analysis of the Doppler signals from supraorbital and common carotid arteries showed sonagram changes both with ageing and with disease. In particular, the ratio of primary peak (A) to secondary peak (B) in systole falls, the A/B ratio being lower in disease than in health. At A/B ratios less than 1.05 there was an 88% probability of disease at the carotid junction. 36/48 (75%) diseased junctions were detected, including almost all major lesions. The method did not so reliably detect small lesions (less than 2 mm plaques, less than 60% lumen diameter stenosis, and 'minimal atheroma'). In 5/53 normal junctions the A/B ratio was in the disease range. Scanning the carotid junction for turbulence yielded additional information in some cases.

Adolescent↗
PubMed1996

Cardiovascular autonomic regulation in asthmatic children evidenced by spectral analysis of heart rate and blood pressure variability.

The objective of the study was to investigate the features of cardiovascular and respiratory autonomic nervous regulation in asthmatic and control children. Cardiorespiratory reactivity was studied by continuous and non-invasive recording of the electrocardiogram, finger systolic arterial pressure (SAP) and flow-volume spirometry in supine and upright positions and during a deep breathing test in 19 children with bronchial asthma and 10 healthy control children (age 8-11 years). The periodic variability components of R-R intervals (the time between successive heart beats) and SAP in relation to respiration were assessed using spectral analysis techniques. Nine asthmatic children without beta2-agonist medication had a lower respiratory rate and larger high frequency (HF) variability of SAP than the controls, and 10 asthmatic children with beta2-agonist medication had greater low-frequency (LF) variability of SAP and LF/HF ratio of R-R intervals, but their respiratory rate did not differ from the controls. No intergroup differences were found in the postural change of variables. Stable bronchial asthma appears to increase respiratory-induced alterations in systolic blood pressure in children. Beta2-agonist medication, on the other hand, increases sympathetic cardiovascular activity in children with asthma.

Adrenergic beta-Agonists↗
PubMed1998

Effect of diltiazem on sympathetic hyperactivity in patients with vasospastic angina as assessed by spectral analysis of arterial pressure and heart rate variability.

The autonomic nervous system importantly regulates coronary arterial tone and vascular resistance. To evaluate a role of autonomic nervous activity and the effects of calcium antagonist in patients with vasospastic angina (VSA), 13 VSA patients with patent coronary arteries (58+/-8 years) and 8 normal subjects (58+/-12 years) were studied. Arterial pressure and electrocardiogram were continuously recorded with the patient in a supine position under controlled respiration (0.2 Hz). Low-frequency (LF) and high-frequency (HF) components of the beat-to-beat variabilities of systolic arterial pressure and RR interval were then estimated by autoregressive power spectral analysis. The LF power (normalized unit) of both systolic arterial pressure (0.53+/-0.17 vs 0.30+/-0.17, p < 0.01) and RR variabilities (0.51+/-0.20 vs 0.31+/-0.16, p < 0.05) in patients with VSA were greater than that in normal subjects. There was no significant difference in the HF power. Seven patients with VSA who were treated with diltiazem (60 to 200 mg/day) had normalized LF power (normalized unit) of both systolic arterial pressure (0.62+/-0.12 vs 0.33+/-0.16, p < 0.01) and RR variabilities (0.55+/-0.23 vs 0.36+/-0.14, p < 0.05), together with clinical improvement. An increased sympathetic vasomotor tone and cardiac sympathetic predominance may play an important role in patients with VSA. Diltiazem improves these sympathetic hyperactivities.

Angina Pectoris, Variant↗
PubMed1999

Large band spectral analysis and harmful risks of dental turbines.

Previous studies have attributed harmful effects to ultrasonic frequencies and recently many have addressed the problem of early deafness among dentists caused by high-speed air turbines. In this study, we measured the spectra of the sounds generated by high-speed air turbines, ranging from audible to ultrasonic frequencies (0-70 kHz). The hypothesis advanced is that the ultrasound spectrum of high-speed air turbines reaches amplitudes that may be noxious. We performed continuous analyses of the spectra of three bands of turbines (n = 17). Measurements of frontal incidence were made using a Bruel & Kjaer microphone and sonometer. For spectral analysis we used the autoregressive parametric method. Using Akaike's criteria the model weights were fixed at 12. The method used in the present work led to an accuracy in the results of 10(-2) kHz within the same brand of turbine. Results show, in terms of frequencies, the presence of four main peaks: 5.6 kHz +/- 0.73 in the audible range, and 20.1 kHz +/- 2.16, 35.7 kHz +/- 2.56 and 46.5 kHz +/- 0.71 in the ultrasonic range. In a normalized spectrum, the amplitude of the ultrasonic component reaches 115 dBspl for 46.5 kHz and is 76% greater than that of the audible component. Such values, both in terms of frequencies and amplitude, reach levels which may provoke short- or long-term negative physiological disturbances and hearing-damage risk. Further research should be directed to determine to what extent they might induce noxious effects for the dental team.

Analysis of Variance↗
PubMed1999

Spectral analysis of heart rate variability and pulmonary responses to topical applications of 2% aminophylline-based thigh cream.

OBJECTIVE: Noninvasive assessment of the immediate and delayed cardiopulmonary response to a 2% aminophylline-based topical thigh reducing cream. DESIGN: Prospective, double-blind, randomized, counterbalanced study with application of: no cream (NC), placebo cream (PC) or 2% aminophylline cream (AC). SUBJECTS: Nine healthy women (aged: 23+/-3 y; weight: 58+/-3 kg; height: 165+/-7 cm; body fat: 19+/-6%; estimated maximal aerobic fitness VO2max): 40+/-4 ml/kg/min). MEASUREMENTS: Medical history, skin patch test, skinfolds, YMCA submaximal cycle ergometry test, psychological evaluations (POMS and Speilberger STAI-1). Pulmonary function and spectral analysis on heart rate variability, measured immediately post-and 4 h post-treatment, on three separate days within a three-week period. RESULTS: Pulmonary function did not change. The averaged R-R interval (ms) was significantly lower for the immediate post AC treatment, but returned to baseline in 4 h. CONCLUSION: Application of a 2% aminophylline-based thigh cream does not affect pulmonary function, however, it may cause a temporary, transient reduction in the averaged R-R interval.

Administration, Cutaneous↗
PubMedDate not supplied

The physical principles of Doppler and spectral analysis.

The Doppler effect provides an ultrasonic method for the detection of echoes from moving structures, particularly flowing blood. In its most simple form, the continuous wave Doppler offers velocity information without depth resolution and is therefore used mainly for the examination of superficial structures. The pulsed Doppler, in combination with real-time imaging, provides a more flexible tool for the interrogation of selected sites in an ultrasound image for motion and flow. The recent development of Doppler flow imaging, in which limited Doppler information is displayed over an entire ultrasound image, usually in color and in real-time, promises to secure the association between Doppler and conventional ultrasound imaging techniques. Spectral analysis permits features of the Doppler signal to be identified which are associated with hemodynamic phenomena, such as flow disturbance and wave reflection. In addition, it allows the quantitative application of Doppler to the estimation of such physiological variables as velocity, flow rate, and pressure difference.

Blood Flow Velocity↗
PubMed2001

Spectral analysis of human tremor during cognitive tasks.

Many stresses occur in our daily lives. Some of these are part of diseases of the nervous system such as ataxia and neuroses. Certain body tremors may be related to these stresses. The rhythmic movement of various muscle groups, similar to a fast circadian rhythm, is defined as a tremor. These tremors, occurring during cognitive tasks, have been recorded by one-dimensional accelerometer in use in our laboratory. In this expanded study, we recorded three-dimensional body displacements with an optical motion capture system while subjects were performing the tasks of intent listening, reading and mental arithmetic calculations. The recorded displacements were subjected to spectral analysis using the Fast Fourier transform (FFT). The results indicate that the body vibration amplitude spectrum caused by mental arithmetic is significantly increased in the frequency rage of 0.5 to 0.7 Hz, when compared to those recorded during other tasks. The induced tremor, as well as general invisible body micro-vibration, were obtained from the three-dimensional body displacements.

Adult↗
PubMed2000

Key factors influencing bowel function after ileal W-pouch anal anastomosis: a spectral analysis of W-pouch motor activity.

Restorative proctocolectomy with ileal pouch anal anastomosis (IPAA) has become the standard surgical procedure for ulcerative colitis (UC). The purpose of this study was to determine which factors are important to achieve good anal continence after IPAA in terms of the motor activity and pressure-volume relationship. A total of 17 patients with UC who underwent IPAA were evaluated. The internal ileal pouch pressure was transanally measured with and without volume-loading of the pouch which induces the urge to evacuate. The maximum tolerable volume (MTV), first urge volume (FUV), and ileal pouch compliance were calculated and the internal ileal pouch pressure records were subjected to spectral analysis for intensive evaluation of the intraluminal pressure waves. The FUV, correlation of the compliance of the FUV with MTV, and the remaining volume up to the MTV (RVMTV) were analyzed. Compliance of the FUV was significantly correlated with the RVMTV (r = 0.736, P < 0.01). The frequency of the phasic waves in the pouch decreased with length of follow up, reflecting improved function (r = -0.588, P < 0.05). The findings of this intensive analysis of manometric measurement indicate that the key factors in postoperative pouch function are RVMTV and the frequency of phasic waves in the W-pouch.

Adult↗
PubMed1996

Application of autoregressive and Fast Fourier Transform spectral analysis to tricuspid and mitral valve stenosis.

Tricuspid and mitral valve flow area was determined from an apical four-chamber view. Doppler signals were recorded from normal subjects and patients with tricuspid and mitral valve stenosis by using a pulsed Doppler unit. The location of sample volume was chosen at the ventricular side of the valve orifice and within the right ventricular tract. This was done with the aid of an integrated cardiac imaging facility. The analog signal at the output of the Doppler unit was sampled and digitized using an analog/digital interface board and transferred to a personal computer. The data were then analyzed using the Fast Fourier Transform (FTT) and autoregressive (AR) modeling methods of spectral analysis and all the sonograms were obtained. Statistical comparison between the FFT and AR methods was made. The results show that the AR method offers a superior performance over the FFT method as regards the assessment of tricuspid and mitral valve stenosis.

Adult↗
PubMed2004

The effect of ventilation on spectral analysis of heart rate and blood pressure variability during exercise.

Heart rate variability (HRV) and systolic blood pressure variability (BPV) during incremental exercise at 50, 75, and 100% of previously determined ventilatory threshold (VT) were compared to that of resting controlled breathing (CB) in 12 healthy subjects. CB was matched with exercise-associated respiratory rate, tidal volume, and end-tidal CO(2) for all stages of exercise. Power in the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, >0.15-0.4 Hz) for HRV and BPV were calculated, using time-frequency domain analysis, from beat-to-beat ECG and non-invasive radial artery blood pressure, respectively. During CB absolute and normalized power in the LF and HF of HRV and BPV were not significantly changed from baseline to maximal breathing. Conversely, during exercise HRV, LF and HF power significantly decreased from baseline to 100% VT while BPV, LF and HF power significantly increased for the same period. These findings suggest that the increases in ventilation associated with incremental exercise do not significantly affect spectral analysis of cardiovascular autonomic modulation in healthy subjects.

Adult↗
PubMed2000

Power spectral analysis of cardiovascular variability in critically ill neurosurgical patients.

OBJECTIVE: Patients with brain damage exhibit a number of changes in heart rate and cardiovascular control. The aim of this study was to relate changes in autonomic cardiovascular control seen in critically ill neurosurgical patients to the quality of subsequent outcome and survival. DESIGN: Prospective, longitudinal, outcome study. SETTING: Intensive care department of a university teaching hospital. PATIENTS: A total of 29 consecutive neurosurgical patients admitted for > or =2 days to the intensive care department with a Glasgow Coma Scale score < 13 who needed electrocardiographic and invasive arterial monitoring. INTERVENTIONS: Sampling of the electrocardiogram, respiratory rate, and arterial pressure into a personal computer was carried out for > or =60 mins. Power spectral analysis was then applied to the data by using a fast Fourier transformation. Arterial baroreflex sensitivity was determined as the gain of the transfer function between systolic arterial blood pressure and electrocardiograph R-R interval (RRI) variability. All surviving patients were followed up at 3 months postadmission to measure quality of outcome. MEASUREMENTS AND MAIN RESULTS: There were reductions in the total power (p < .01) of RRI variability in those who subsequently died compared with those who survived. This was significant for very low frequency (p < .001) and low-frequency (LF) (p < .05) but not high-frequency (HF) bands (p = .11). Blood pressure variability, however, did not change between groups. Baroreflex sensitivity was 8.7+/-2.2 msecs/mm Hg for patients with a good later outcome and 4.4+/-1.5 msecs/mm Hg for patients who subsequently died (p = .03). Patients who recovered to a good quality outcome also had a raised LF/HF ratio in RRI (p = .05). CONCLUSION: A reduction in the total power variability of RRI and a lowered LF/HF ratio of the RRI are associated with a poor quality recovery or death after neurosurgical illness. A reduction in the baroreflex was specifically associated with death in this patient group.

Adult↗
PubMed1992

Power spectral analysis of heart rate variability in Type As during solo and competitive mental arithmetic task.

It has been reported that there are differences in autonomic balance between Type As and Type Bs. This study evaluated the sympathovagal interaction in Type A (N = 10) and Type B (N = 10) male students during mental arithmetic task in a solo and a competitive condition by the spectral component analysis of heart rate variability (HRV). The low-frequency (LF) component to high-frequency (HF) component ratio was significantly greater in Type As than in Type Bs, though no significant differences were found in task performance, heart rate change, and blood pressure between the two subject groups in both conditions. The present findings indicate that there was a significant difference in sympathovagal balance between Type As and Type Bs, and that Type As showed dominant sympathetic activity. The results suggest that the power spectral analysis of HRV, which is convenient and non-invasive, has enough sensitivity to discriminate differences in autonomic balance between Type A subjects and Type B subjects, not only during the solo and competitive task period but also during the resting period.

Heart Rate↗
PubMed1997

[Spectral analysis of R-R intervals in adolesent persons during mental stress].

In this study, power spectrum analysis of the autoregressive model was used to quantitatively estimate the power spectrum of R-R intervals in adolesent during the state of the mental stress. The power spectrum density of the lower frequency (HF: 0.05-0.15 Hz) and the high frequency (HF: 0.15-0.5 Hz) component were acquired. The results showed that during the mental stress the HF component decreased significantly (P < 0.001) while the LF component increased relatively and the center frequency of the HF increased remarkably (P < 0.001). This suggests that the spectral analysis of heart rate variability (R-R interval) offers an efficient non-invasive method to assess the autonomic nerve activity of cardiovascular system during the stress condition.

Adult↗