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PubMed1999

Early autonomic dysfunction in patients with diabetes mellitus assessed by spectral analysis of heart rate and blood pressure variability.

Patients with diabetes mellitus (DM) often have alterations of the autonomic nervous system (ANS), even early in their disease course. Previous research has not evaluated whether these changes may have consequences on adaptation mechanisms in DM, e.g. to mental stress. We therefore evaluated whether patients with DM who already had early alterations of the ANS reacted with an abnormal regulatory pattern to mental stress. We used the spectral analysis technique, known to be valuable and reliable in the investigation of disturbances of the ANS. We investigated 34 patients with DM without clinical evidence of ANS dysfunction (e.g. orthostatic hypotension) and 44 normal control subjects (NC group). No patients on medication known to alter ANS responses were accepted. The investigation consisted of a resting state evaluation and a mental stress task (BonnDet). In basal values, only the 21 patients with type 2 DM were different in respect to body mass index and systolic blood pressure. In the study parameters we found significantly lower values in resting and mental stress spectral power of mid-frequency band (known to represent predominantly sympathetic influences) and of high-frequency and respiration bands (known to represent parasympathetic influences) in patients with DM (types 1 and 2) compared with NC group (5.3 +/- 1.2 ms2 vs. 6.1 +/- 1.3 ms2, and 5.5 +/- 1.6 ms2 vs. 6.2 +/- 1.5 ms2, and 4.6 +/- 1.7 ms2 vs. 6.2 +/- 1.5 ms2, for resting values respectively; 4.7 +/- 1.4 ms2 vs. 5.9 +/- 1.2 ms2, and 4.6 +/- 1.9 ms2 vs. 5.6 +/- 1.7 ms2, and 3.7 +/- 2.1 ms2 vs. 5.6 +/- 1.7 ms2, for stress values respectively; M/F ratio 6/26 vs. 30/14). These differences remained significant even when controlled for age, sex, and body weight. However, patients with DM type 2 (and significantly higher body weight) showed only significant values in mental stress modulus values. There were no specific group effects in the patients with DM in adaptation mechanisms to mental stress compared with the NC group. These findings demonstrate that power spectral examinations at rest are sufficiently reliable to diagnose early alterations in ANS in patients with DM. The spectral analysis technique is sensitive and reliable in investigation of ANS in patients with DM without clinically symptomatic autonomic dysfunction.

Adult↗
PubMed1982

Power spectral analysis of auditory brain stem responses to pure tone stimuli.

Power spectral analysis and digital filtration of the auditory brain stem responses to tone burst stimuli were carried out in three adult subjects with normal hearing. Three dominant peaks (peaks A. B, C), ranging in frequency 50-150, 500-600, and 1000-1100 Hz, were observed in the spectrograms of the responses to 4 kHz at 80 dB SL. Power of higher frequency components (peaks B and C) decreased markedly or disappeared completely with decreased intensity as well as decreased frequency of stimulus, while peak A around 100 Hz consistently appeared regardless of stimulus intensity or frequency. Main spectral components of the individual waves in the ABR were determined as follows: peak A for the slow positive deflection in the response, peak B for waves VI and VII, peak C for waves II and IV, and peaks B and C for waves I, III and V.

Acoustics↗
PubMed2002

Rapid quantitative assessment of myocardial perfusion: spectral analysis of myocardial contrast echocardiographic images.

We described a novel rapid spectral analysis technique performed on raw digital in-phase quadrature (IQ) data that quantitatively differentiated perfused from nonperfused myocardium based on the simultaneous comparison of local fundamental and harmonic frequency band intensity levels. In open-chest pigs after ligation of the left anterior descending coronary artery (LAD) and continuous venous contrast infusion, the fundamental-to-harmonic intensity ratio (FHIR) for samples placed within the left ventricular (LV) cavity (10.8 +/- 1.7 dB) and perfused myocardium (13.7 +/- 1.6 dB) were significantly (P <.001) lower than for nonperfused myocardium (27.1 +/- 2.9 dB). In attenuated images, the FHIR for the LV cavity and perfused myocardium were also significantly (P <.05) lower than for the nonperfused myocardium (21.4 +/- 3.0 dB, 34.4 +/- 3.2 dB, and 40.2 +/- 4.4 dB, respectively). Spectral properties of contrast microbubbles, as characterized by the FHIR, allow for rapid quantitative assessment of myocardial perfusion from data contained in a single-image frame, without requiring background image subtraction and image averaging.

Acute Disease↗
PubMedDate not supplied

Power spectral analysis of the EEG following protein malnutrition.

In these studies, power spectral analysis techniques were utilized to quantify the EEG obtained from rats reared on either an 8% or 25% casein diet during various vigilance states at two stages of development: (1) adulthood-90 to 120 days old; and (2) immediately after weaning-22 to 23 days old. It was found that the cortical EEG contained relatively more power in the low frequencies (ie., 0.5 to 10 Hz) for the 22-23 day old animals than for the 90-120 day old rats, especially during the slow wave sleep states-SWS1 and SWS2. Theta activity (5-8 Hz) in the hippocampus was shown to have greater power for the 22-23 day old group than for the older animals during both REM sleep and waking. Analyses of power spectral data and other indices of the frequency distribution of the hippocampal EEG indicated that those animals subjected to protein malnutrition have significantly more power in the theta band during REM sleep than the normal adult group. Since it was also noted that the hippocampal EEG obtained from the 22-23 day old group contained relatively more power in the theta band than the 90-120 day old group, the dietary treatment effect might be intrepreted as an instance of retarded development associated with protein malnutrition. Thus, a significant effect of the dietary manipulation used in the study may be largely on the system responsible for regulating theta activity.

Age Factors↗
PubMed1999

Hemodynamic patterns and spectral analysis of heart rate variability during dialysis hypotension.

Intradialytic hypotension, a major source of morbidity during hemodialysis and ultrafiltration, is often accompanied by paradoxical bradycardia. Relatively little is known about the sequential changes in autonomic nervous system activity up to and during the hypotensive episode. Continuous, beat-to-beat measurements of BP and heart rate were made during hemodialysis in patients prone (n = 8) and not prone (n = 11) to develop intradialytic hypotension. Off-line spectral analysis of heart rate variability (HRV) was performed to assess changes in autonomic nervous system activity during dialysis sessions both with and without hypotension. The low frequency (LF) component of HRV is thought to correlate with sympathetic nervous system activity, the high frequency (HF) component with that of the parasympathetic nervous system. In the sessions not complicated by symptomatic hypotension (n = 26), mean arterial BP (MAP) hardly fell, whereas heart rate increased from 77 +/- 2 to 89 +/- 5 bpm (P < 0.05). The LF component of HRV increased from 45.2 +/- 5.0 normalized units (nu) to 59.9 +/- 4.9 nu (P < 0.05), whereas the HF component fell from 54.8 +/- 5.0 to 40.2 +/- 4.4 nu (P < 0.05). These changes agree with compensatory baroreflex-mediated activation of the sympathetic nervous system (and suppressed parasympathetic activity) during ultrafiltration-induced intravascular volume depletion. In the sessions complicated by severe symptomatic hypotension (n = 22), the changes in heart rate and the results of spectral analysis of HRV were similar to those reported above up to the moment of sudden symptomatic (nausea, vomiting, dizziness, cramps) hypotension, whereas MAP had already fallen gradually from 94 +/- 3 to 85 +/- 3 mmHg (P < 0.05). The sudden further reduction in MAP (to 55 +/- 2 mmHg, P < 0.02) was invariably accompanied by bradycardia (heart rate directly before hypotension 90 +/- 2 bpm, during hypotension 69 +/- 3 bpm, P < 0.002). The LF component of HRV fell from 62.8 +/- 4.6 nu directly before to 40.0 +/- 3.7 nu (P < 0.05) during hypotension, whereas the HF component increased from 37.9 +/- 4.7 to 60.3 +/- 3.7 nu (P < 0.05). These findings agree with activation of the cardiodepressor reflex, involving decreased sympathetic and increased parasympathetic nervous system activity, respectively. These findings indicate that activation of the sympatho-inhibitory cardiodepressor reflex (Bezold-Jarisch reflex), which is a physiologic response to a critical reduction in intravascular volume and cardiac filling, is the cause of sudden intradialytic hypotension.

Aged↗
PubMed1980

[Spectral analysis of a "sea gull cry" murmur (author's transl)].

"Precordial honk" is a loud, high pitched, musical and usually intermittent systolic noise. The concept of extracardiac origin and "inocence" of this finding is superseded and today its valvular origin during mitral prolapse, mitral or tricuspidal insufficiency - due to rheumatic or ischaemic disease - or during cardiomiopathy is demonstrated. The acoustic characterization of this finding was based on phonocardiographic registration. All the authors describe the "precordial honk" as a high frequency murmur without specifying the acoustic characteristics of the phenomenon. A spectral analysis technique applied to the acoustic cardiac signal (Fourier analysis) has been employed in order to study the "precordial honk" of a 15-year-old boy with mitral valve prolapse. This made possible to show that this sound had only one fundamental frequency at 300 Hz. without harmonics; a "sea gull cry" murmur (as the cry of many birds is) justifying the name given by clinicians. The spectral analysis of phonocardiography signal allow to study, more precisely, the cardiac acoustic phenomenon.

Adolescent↗
PubMed2003

Spectral analysis of respiratory noise in horses with upper airway disorders.

REASONS FOR PERFORMING STUDY: It has long been recognised that the production of abnormal respiratory sounds by horses during exercise is frequently associated with upper airway obstructions. Respiratory acoustic measurements have shown promise in investigation of upper airway disorders in man and, more recently, in horses with experimentally-induced obstructions. OBJECTIVES: To evaluate sounds from exercising horses with naturally occurring dynamic obstructions of the upper respiratory tract and to compare these with those from normal horses in order to determine whether different obstructions produce characteristic spectral patterns. METHODS: The audio signal, airflow and videoendoscopic images were recorded simultaneously during an incremental exercise test on a high-speed treadmill. RESULTS: Spectral analysis of the audio signal showed marked differences between control and clinically afflicted horses. Dorsal displacement of the soft palate was characterised by a narrow low frequency (20-80 Hz) peak during expiration. Horses with dynamic laryngeal collapse produced inspiratory sounds characterised by a broad band high frequency spectral component in the range 1.1-2.7 kHz. CONCLUSIONS AND POTENTIAL RELEVANCE: Spectral analysis of respiratory sounds in horses has potential as a diagnostic technique for field use especially when facilities for high-speed treadmill assessment are not practicable.

Airway Obstruction↗
PubMed2000

Cross-spectral analysis of heart rate and blood pressure modulations.

The cross-spectral analysis of heart rate (HR) and blood pressure (BP) variabilities provides "amplitude" and "phase" related measures. Compared to the amplitude measure, that is the baroreflex gain, the phase related measure characterizing the time lag between HR and BP oscillations has been studied to a much lesser extent. A population of 103 patients (73 men, 30 women, aged 53 +/- 12, range 20-82 years) referred for the management of coronary artery disease and/or hypertension were studied. In each subject, electrocardiogram and BP recordings were obtained in the supine and sitting positions of 5 minutes of rest (spontaneous respiration), 3 minutes of controlled respiration at 0.1 Hz (slow-controlled respiration), and 3 minutes of controlled respiration at 0.33 Hz (fast-controlled respiration). The frequency of maximum coherence (above the arbitrary threshold of 0.5) of BP and RR interval variabilities was searched between 0.033-0.133 Hz and 0.200-0.400 Hz to obtain baroreflex gain and phase shift in low and high frequency bands, respectively. Mean phase shifts of -79.1 and -67.0 degrees (-2.4 and -2.1 s) were found during slow-controlled respiration in the supine and sitting body positions, respectively. The mean phase shift between systolic BP and RR interval in the low frequency band was found between 83 and -109 degrees for body positions and respiration regimes. The actual baroreflex related time lag between systolic BP and RR variations was found between 3.5 and 5.1 seconds. The study concludes that the appropriate, and not always easy, selection of the frequency of maximum coherence between BP and HR oscillation is crucial for an accurate cross-spectral assessment of baroreflex sensitivity.

Adult↗
PubMed1993

Effect of method and parameters of spectral analysis on selected indices of simulated Doppler spectra.

The sensitivity of Doppler spectral indices (mean frequency, maximum frequency, spectral broadening index and turbulence intensity) to the conditions of spectral analysis (estimation method, data window, smoothing window or model order) increases with decreasing signal bandwidth and growing index complexity. The bias of spectral estimate has a more important effect on these indices than its variance. A too low order, in the case of autoregressive modeling and minimum variance methods, and excessive smoothing, in the case of the FFT method, result in increased errors of Doppler spectral indices. There is a trade-off between the errors resulting from a short data window and those due to insufficient temporal resolution.

Arteries↗
PubMed1981

Spectral analysis of chlorophyll-protein complexes from higher plant chloroplasts.

A spectral analysis of chlorophyll-protein complexes was carried out to gain information about the state of chlorophyll in vivo. A light-harvesting chlorophyll a/b protein complex and a Photosystem I complex were isolated from pea and from wheat chloroplasts by treatment with 0.5% Triton and centrifugation in a sucrose gradient. Resolution of absorption spectra (89K) of these fractions showed that their forms of chlorophyll were not altered by the isolation procedure. However, because the sum of the spectra of the fractions had a different shape from the chloroplast, it may be assumed that a third chlorophyll-protein complex was lost or changed in terms of the state of its chlorophyll. The spectrum of this missing chlorophyll was calculated and found to have a maximum near 683 nm. Circumstantial evidence indicates that this calculated spectrum may represent the native absorption of antenna chlorophyll a-protein of Photosystem II. The proportionality between the major absorbing forms of chlorophyll observed by curve analysis of different fractions suggests that the 660 and 678 nm forms may be the result of exciton interaction. The addition of a very small, narrow 675 nm band caused a very large improvement in fitting the spectrum of the antenna chlorophyll a/b protein with component bands, but not in Photosystem I spectra. A direct comparison of curve resolution with fourth derivative analysis shows the advantages of the former for studying the states of chlorophyll in vivo.

Chlorophyll↗
PubMed1995

Assessment of autonomic function in traumatic quadriplegic and paraplegic patients by spectral analysis of heart rate variability.

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart rate variability (HRV) of quadriplegic and paraplegic male subjects at rest in the supine position. In agreement with our previous study, in nine of 15 quadriplegic patients only the high-frequency (HF: center frequency = respiratory frequency) component (a marker of vagal modulation of heart rate) was observed. In contrast, in six of the quadriplegic patients both the HF component and the low-frequency (LF: center frequency at approx. 0.1 Hz, 0.03-0.15 Hz in this study) component (a marker of sympathetic and vagal modulation of heart rate) were observed. However, in six quadriplegic patients who presented the LF component, (i) the center frequency of the LF component was lower than that in 10 healthy, sedentary, age-matched males (control I) (P < 0.01), (ii) the power of the HF component was smaller than that in the control-I group (P < 0.01) and (iii) the LF/HF power ratio (an index of sympathovagal balance) was larger than that in the control-I group (P < 0.05). On the other hand, in nine paraplegic patients with an intact 1st-4th thoracic spinal cord, from which the cardiac sympathetic nerves originate, the total power, the power of the LF component and that of the HF component were smaller than those in nine healthy, sedentary, age-matched males (control II) (P < 0.05, P < 0.01 and P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

Spectral analysis of the normal electrocardiogram in children and adults.

We performed spectral analysis of the X-lead Frank VCG from six normal adults (Group A) and eight normal children (Group B) using a Fast Fourier Transform. The Group A magnitudes were consistently and significantly lower than Group B in the 20--90 Hz region. Similarly, the -40 dB point was 75 Hz for Group A and 107 Hz for Group B. The P waves of the two groups had similar spectra, as did their T waves. When the entire cardiac cycle was analyzed, there was again a consistent and significant difference in the frequencies from 25--80 Hz. Despite the significant differences in the Group A and B spectra, the vast majority of the information contained in the ECG signal was confined to frequencies below 100 Hz. Therefore, a bandwidth of 100 Hz is probably adequate for accurate recording of the ECG signal from children, as well as from adults.

Adult↗
PubMed2000

Spatial spectral analysis of human electrocorticograms including the alpha and gamma bands.

Spatial spectral analysis is essential for deriving spatial patterns from simultaneous recordings of electrocorticograms (ECoG), in order to determine the optimal interval between electrodes in arrays, and to design spatial filters, particularly for extraction of information about the dynamics of human gamma activity. ECoG were recorded from up to 64 electrodes 0.5 mm apart in a linear array 3.2 cm long, which was placed on the exposed superior temporal gyrus or motor cortex of volunteers undergoing diagnostic surgery. Visual displays of multiple traces revealed broad spectrum oscillations in episodic bursts having a common aperiodic wave form with recurring patterns of spatial amplitude modulation (AM patterns) on selected portions of the array. The one-dimensional spatial spectrum of the human ECoG was calculated at successive time samples and averaged over periods of up to 20 s. Log power decreased monotonically with increasing log spatial frequency in cycles/mm (c/mm) to the noise level approximately 2 log units below maximal power at minimal frequency (0.039+/-0.002 c/mm). The inflection point at 0.40+/-0.05 c/mm specified an optimal value for a low pass spatial filter to remove noise, and an optimal interelectrode spacing of 1.25 mm to avoid undersampling and aliasing. An 8 x 8 array with that spacing would be 10 x 10 mm.

Adolescent↗
PubMed2001

Power spectral analysis of heart rate variability in rats as a quantitative tool in the PK-PD analysis of the parasympatholytic activity of atropine.

PURPOSE: To utilize power spectral analysis (PSA) of heart rate variability (HRV) as a pharmacodynamic (PD) measure of atropine parasympathetic effect, and to model the kinetics of action. METHODS: Heart rate data was collected following atropine administration to rats and was analyzed off-line for high frequency peaks by PSA of HRV as a measure of parasympathetic tone. A temporal cumulative approach (TCA) detected transient changes in parasympathetic activity. The pharmacokinetics (PK) was analyzed and linked to both direct and indirect PK-PD models. RESULTS: TCA enabled a quantitative measure of atropine parasympathetic activity. A simultaneous fit of the indirect PK-PD model to the experimental data of all three atropine doses successfully captured the experimental data. CONCLUSIONS: TCA can be used as a quantitative measure of parasympathetic tone. Our work has established a preclinical model to investigate the kinetics of drug action on the autonomic nervous system.

Animals↗
PubMed1999

Uremic autonomic neuropathy studied by spectral analysis of heart rate.

BACKGROUND: There is good evidence that power spectral analysis (PSA) of heart rate variability may provide an insight into the understanding of autonomic disorders. METHODS: We investigated 30 chronic uremic patients who were on periodic bicarbonate hemodialysis by a battery of six cardiovascular autonomic tests (beat-to-beat variations during quiet breathing and deep breathing, heart rate responses to the Valsalva maneuver and standing, blood pressure responses to standing and sustained handgrip) and PSA of heart rate variations. RESULTS: Eleven patients (37%) had an abnormal response to only one parasympathetic test. Twelve patients (40%) had a definite parasympathetic damage, as indicated by at least two abnormal heart rate tests, whereas four (13%) had combined parasympathetic and sympathetic damage. Multivariate analysis of the cardiovascular tests revealed that 19 patients (63%) had moderate-to-severe autonomic neuropathy (AN), and 11 patients exhibited normal autonomic function. Among the symptoms suggestive of autonomic dysfunction, only impotence in males was significantly associated with test-proven AN. The PSA of the heart rate variability demonstrated a good discrimination of low-frequency (LF) and high-frequency (HF) bands (LF, 0.03 to 0.15 Hz; HF, 0.15 to 0.33 Hz) among controls, uremic patients without test-proven AN, and uremic patients with test-proven AN. A significant reduction of the LF value on supine uremic patients without AN suggests that an early sympathetic involvement exists that traditional autonomic tests were unable to detect. CONCLUSIONS: Our study indicates that the current opinion of a major parasympathetic damage in chronic uremic patients on hemodialysis has to be modified in favor of a more widespread autonomic dysfunction involving both the sympathetic and parasympathetic pathways.

Adult↗
PubMed1989

[Power spectral analysis of EEG during simple deep hypothermia under ether anesthesia].

Power spectral analysis of electroencephalogram was performed during simple deep hypothermia under ether anesthesia, compared with that during hypothermic cardiopulmonary bypass under morphine anesthesia. In ether anesthesia group, EEG isoelectricity developed at average esophageal temperature of 27.2 degrees C which is higher than the temperature previously reported. This remarkable depression of the EEG may be due to deep ether anesthesia, because severe hypotension episodes were not associated with this and no neurological complication was noticed post-operatively. In cardiopulmonary bypass group, EEG activity persisted throughout the procedures even at the lowest esophageal temperature reached of 22.3 degrees C. In ether anesthesia group, the temperature at which EEG activity reappeared correlated with the duration of circulatory arrest. During simple deep hypothermia under ether anesthesia, the EEG is not useful to detect brain ischemia during cooling period, because EEG activity was lost in the early course of cooling, but during rewarming period the EEG demonstrated depression of cerebral function due to total circulatory arrest.

Anesthesia↗
PubMedDate not supplied

[Spectral analysis of EEG signals in Alzheimer's disease].

UNLABELLED: Alzheimer's disease (AD) represents the most frequent cause of senile dementia in Western countries. The disease has a slow onset and gradual progress. Over the past few years considerable importance has been attributed to the diagnostic techniques of brain imaging able to highlight morphological and functional images. EEG mapping is one of the most widely used methods. METHODS: The authors evaluated the characteristics of EEG mapping in relation to frequency and amplitude in a group of elderly patients with AD and in a group of healthy elderly control subjects. The former group consisted of 10 patients with AD aged between 65 and 83 years old. The control group included 10 healthy subjects who were matched for age and sex. RESULTS: The spectral analysis of EEG signals relating to frequency and amplitude showed a slowing down of underlying activity in AD patients, with a frequency between 1 and 4 c/sec, amplitudes below 5 microW and no arrest reaction. In healthy subjects spectral analysis showed a signal percentage colocated at a frequency of between 8 and 13 c/sec in relation to frequency. CONCLUSIONS: In view of these results, the authors recommend the use of EEG mapping to complete the diagnosis of Alzheimer's disease in the aged.

Aged↗
PubMedDate not supplied

Frequency specificity of amplitude-modulation-following response detected by phase spectral analysis.

To investigate the frequency specificity of steady-state responses elicited with a sinusoidally amplitude-modulated tone (amplitude-modulation-following response, AMFR), AMFR at different carrier frequencies were examined in 15 subjects with normal hearing, 12 patients with abrupt high-frequency hearing loss, 5 patients with low-frequency hearing loss and 1 patient with mid-frequency hearing loss. The stimulus was a sinusoidally amplitude-modulated tone with a modulation frequency of 40 Hz and modulation depth of 95%. Carrier frequencies were from 250 to 4000 Hz in normal subjects and from 250 to 8,000 Hz in hearing-impaired subjects. Fridman's phase spectral analysis was conducted for automatic detection of response. The thresholds of AMFR were distributed within 30 dB nHL at all carrier frequencies in normal subjects. In the hearing-impaired subjects, AMFR thresholds were between 0 and 25 dB above the behavioral threshold at all carrier frequencies. The threshold patterns of AMFR detected by phase spectral analysis very closely resembled the corresponding audiogram patterns in all types of hearing impairment. AMFR is thus shown to have a very good frequency specificity.

Acoustic Stimulation↗