SEARCH · Search PubMed

Results for “Spectral Analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources

PubMed2005

Isotopomer spectral analysis of intermediates of cholesterol synthesis in patients with cerebrotendinous xanthomatosis.

Four patients with cerebrotendinous xanthomatosis (CTX) and 2 healthy controls received a constant proximal intraduodenal infusion of 1- 13 C-acetate as a stable-isotope-labeled marker of sterol synthesis. One patient was treated with pravastatin (20 mg twice daily) and another patient with chenodeoxycholic acid (250 mg tid). Every hour, venous blood and duodenal samples were obtained. Stable-isotope enrichment of neutral and polar sterols in serum and bile was assessed by gas chromatography/mass spectrometry. Isotopomer spectral analysis was performed on cholesterol, lathosterol, Delta-8-cholesterol, methylsterol, and lanosterol. Stable-isotope labeling of cholestanol, bile acids, and bile alcohols was analyzed by assessing the change over time of the ratio of M + 3 to M + 0. Eleven hours after marker infusion, we found up to 50% newly synthesized lathosterol in serum and up to 80% in bile, with similar results for other cholesterol precursors. In cholesterol, stable-isotope labeling could be demonstrated in all study subjects with a more prominent labeling in bile than in serum. No stable-isotope labeling was detected in cholestanol. Only minor stable-isotope incorporation was detectable in polar sterols in some subjects. Therapy with pravastatin did not have any effect on fractional or absolute synthesis rates or on the concentrations of cholestanol or cholesterol precursors compared to untreated patients with CTX. In contrast, therapy with chenodeoxycholic acid markedly lowered the concentrations of cholestanol and cholesterol precursors, led to a disappearance of bile alcohols, and reduced absolute synthesis rates of lathosterol. Isotopomer spectral analysis proved to be a powerful method to assess the endogenous synthesis of cholesterol precursors in patients with CTX. Higher fractional synthesis in bile than in serum may be due to the size of the pools in bile vs serum. Cholestanol exhibits no marker uptake and is therefore probably synthesized from preformed cholesterol. Biliary cholesterol secretion in patients with CTX is decreased compared to healthy controls.

Adult↗

PubMed2005

Prediction of vestibulo-autonomic symptoms during the caloric test: evaluation of autonomic activity by spectral analysis of the electrocardiographic R-R interval.

CONCLUSION: If the high-frequency (HF) component of the R-R interval spectrum of the electrocardiogram (ECG) increases after the first stimulation during a bithermal caloric test, subsequent repeated stimulations may be likely to induce autonomic symptoms such as nausea. OBJECTIVE: Nausea often occurs as a vestibulo-autonomic symptom during the caloric test. However, there have been only a few clinical studies of autonomic activity during this test. To determine whether certain factors can predict the development of nausea, we performed an autonomic function test by means of R-R interval spectral analysis of the ECG during caloric testing. MATERIAL AND METHODS: The study subjects were 53 healthy volunteers aged 22-39 years (41 males, 12 females; mean age 25.3 years) and a 35-year-old male patient with a labyrinthine defect. The caloric test was performed in 43 subjects using an air caloric apparatus with bithermal stimulation of alternate ears. After each stimulation, the subjects were asked about autonomic symptoms. Serial ECG records were obtained and R-R interval spectral analysis was performed. RESULTS: Severe nausea was observed in 12 subjects (28%). In the group with severe nausea, the HF component of the R-R interval spectrum increased after the first caloric stimulation when autonomic symptoms had not yet become marked.

Adult↗

PubMed2005

Spectral analysis identifies sites of high-frequency activity maintaining atrial fibrillation in humans.

BACKGROUND: The identification of sites of dominant activation frequency during atrial fibrillation (AF) in humans and the effect of ablation at these sites have not been reported. METHODS AND RESULTS: Thirty-two patients undergoing AF ablation (19 paroxysmal, 13 permanent) during ongoing arrhythmia were studied. Electroanatomic mapping was performed, acquiring 126+/-13 points per patient throughout both atria and coronary sinus. At each point, 5-second electrograms were obtained to determine the highest-amplitude frequency on spectral analysis and to construct 3D dominant frequency (DF) maps. The temporal stability of the recording interval was confirmed in a subset. Ablation was performed with the operator blinded to the DF maps. The effect of ablation at sites with or without high-frequency DF sites (maximal frequencies surrounded by a decreasing frequency gradient > or =20%) was evaluated by determining the change in AF cycle length (AFCL) and the termination and inducibility of AF. The spatial distribution of the DF sites was different in patients with paroxysmal and permanent AF; paroxysmal AF patients were more likely to harbor the DF site within the pulmonary vein, whereas in permanent AF, atrial DF sites were more prevalent. Ablation at a DF site resulted in significant prolongation of the AFCL (180+/-30 to 198+/-40 ms; P<0.0001; kappa=0.77), whereas in the absence of a DF site, there was no change in AFCL (169+/-22 to 170+/-22 ms; P=0.4). AF terminated during ablation in 17 of 19 patients with paroxysmal and 0 of 13 with permanent AF (P<0.0001). When 2 patients with nonsustained AF during mapping were excluded, 13 of 15 (87%) had AF termination at DF sites (54% at the initially ablated DF site): 11 pulmonary veins and 2 atrial. In addition, AF could no longer be induced in 69% with termination of AF at a DF site. There were no significant differences in the number or percentage of DF sites detected (5.4+/-1.6 versus 4.9+/-2.1; P=0.3) and ablated (1.9+/-1.0 versus 2.4+/-1.0; P=0.3) in those with and without AF termination. The duration of radiofrequency ablation to achieve termination was significantly shorter than that delivered in those with persisting AF (34.8+/-24.0 versus 73.5+/-22.9 minutes; P=0.0002). All patients with persisting AF had additional DF sites outside the ablated zones. CONCLUSIONS: Spectral analysis and frequency mapping identify localized sites of high-frequency activity during AF in humans with different distributions in paroxysmal and permanent AF. Ablation at these sites results in prolongation of the AFCL and termination of paroxysmal AF, indicating their role in the maintenance of AF.

Amiodarone↗

PubMed2006

MALDI-TOF mass spectral analysis of siRNA degradation in serum confirms an RNAse A-like activity.

Synthetic siRNA duplexes are used widely as reagents for silencing of mRNA targets in cells and are being developed for in vivo use. Serum stability is a major concern if siRNA is to be used for therapeutic delivery within blood circulation. We have developed the use of MALDI-TOF mass spectrometry as a rapid and convenient analytical tool to identify the most vulnerable sites within siRNA to serum degradation. Using this approach, we found that one siRNA duplex (Dh3) with UpA sequences close to one end was particularly vulnerable to rapid cleavage. This produced a fragment of mass consistent with the presence of a 2',3'-cyclic phosphate that was slowly hydrolysed to a 2'-(3'-)phosphate on extended incubation. Substitution of these sites with 2'-O-methyl U residues prevented cleavage and confirmed that the major pathway for initial degradation is via cleavage by an RNAse A-like activity. Mass spectral analysis was used to follow the serum degradation of siRNA over more prolonged periods to show the accumulation of many fragments, almost all showing cleavage following pyrimidine nucleoside residues. Overall, the MALDI-TOF mass spectral analysis technique should prove useful for preliminary screening of the serum stability of siRNA duplexes and for identification of the most vulnerable cleavage sites.

Base Sequence↗

PubMed1994

Accuracy of beat-to-beat noninvasive measurement of finger arterial pressure using the Finapres: a spectral analysis approach.

OBJECTIVE: Our objective was to test the accuracy of noninvasive recordings of finger arterial pressure (FAP) using the Ohmeda Finapres (Ohmeda Monitoring Systems, Englewood, CO). METHODS: Twenty patients, aged 20 to 78 years, requiring admission to the intensive care unit and placement of intraarterial catheters participated in the study. Systolic and diastolic pressures were derived from 1-hr recordings of beat-to-beat FAP and from ipsilaterally recorded intraarterial pressure (IAP) signals. In all 20 cases, we analyzed beat-to-beat discrepancies between the actual magnitude of FAP and IAP, as well as the distribution of the consecutive differences within each of the two signals. In 10 cases, spectral analysis of the frequency content of both signals was performed. RESULTS: The average systolic FAP (128.1 +/- 22.4 mm Hg) did not differ from IAP (127.1 +/- 19.7 mm Hg), whereas diastolic FAP (78.1 +/- 11.9 mm Hg) was greater (71.5 +/- 10.3 mm Hg) (p < 0.001). No differences in the linear trends of FAP and IAP were observed. Overall, systolic FAP and IAP were discrepant by 0.84 +/- 13.3 mm Hg (-21.82 to 25.8 mm Hg); diastolic FAP and IAP were discrepant by 6.67 +/- 5.23 mm Hg (2.68 to 13.05 mm Hg). Despite discrepancies in the magnitude of the two signals, the contour of IAP approximated that of FAP. Spectral analysis demonstrated good reproducibility and coherence between diastolic IAP and FAP fluctuations in both low-frequency (0.01 to 0.15 Hz) and high-frequency (0.15 to 0.33 Hz) bands. The low-frequency fluctuations in FAP systolic pressure were significantly amplified (p < 0.001) (gain 1.75), whereas the high-frequency fluctuations were not. CONCLUSIONS: Over the course of 1 hr, FAP followed the contour and frequency content of IAP.

Adult↗

PubMed1987

Correlation and spectral analysis of relations between single unit discharge and muscle activities.

Correlation and spectral analysis was used to study functional linkages between single-cell discharge in the magnocellular red nucleus and the electromyographic activity of several limb muscles. Long sequences of unit discharge and EMG activity were recorded while feline subjects performed a food retrieval task. Unit discharge and muscle activity were patterned in bursts that corresponded to different phases of the task. There was sufficient variability in the parameters of these bursts to regard the signals as pseudorandom variables, thus facilitating a correlation analysis. Cross-correlation functions computed between unit discharge and each muscle EMG served to characterize the strength and reliability of linkages between a single unit and various limb muscles. Auto-correlation and auto-spectral density functions provided summary measures of the temporal and frequency characteristics of the signals. Power in the signals was concentrated in a behaviorally relevant range (0.2-8 Hz). Coherence functions showed peaks that indicated which frequency components were well correlated with unit discharge. Two-sided impulse responses served to characterize the dynamic properties of the linkages. These methods are shown to be valuable in characterizing noncausal, as well as causal, linkages through multisynaptic pathways in the nervous system.

Action Potentials↗

PubMed1997

Autonomic nervous function during haemodialysis assessed by spectral analysis of heart-rate variability.

1. Short-term autonomic response to haemodialysis-induced hypovolaemia was studied in 30 patients undergoing chronic haemodialysis by analysing power spectra of heart-period variability. Patients were classified as haemodynamically stable (15 patients) and unstable (15 patients) according to their past history of cardiovascular collapse during the treatment. Blood volume, systolic arterial pressure and heart period were measured during sessions that ended without the occurrence of collapse. 2. No significant differences were observed when comparing blood volume, heart rate and arterial pressure of stable and unstable patients during the dialysis, and the two groups could not be distinguished merely on the basis of these haemodynamic parameters. Conversely, spectral analysis of beat-to-beat heart-period variability showed markedly different power patterns: in stable patients power was mainly in the low-frequency (LF) band (0.06-0.15 Hz), whereas in unstable patients it was mainly in the high-frequency (HF) band (0.15-0.4 Hz). 3. The efficiency of the autonomic response to hypovolaemia was evaluated by the ratio between the powers in the LF and HF bands. Stable patients exhibited an LF/HF power ratio systematically greater than unstable patients during the entire dialysis, and on the basis of this index the two groups were clearly separated. 4. Results obtained with spectral analysis lead us to conclude that reduced efficiency in the autonomic control of cardiovascular functions could be the main cause of the haemodynamic instability of patients prone to collapse.

Aged↗

PubMed1997

Vegetative background of sleep: spectral analysis of the heart rate variability.

Phasic events during sleep, either arousal or REM-burst related, and the associated transient cardiovascular responses have been the subject of intensive research in previous studies. However, nontransient (stationary) fluctuations in heart rate have been studied less extensively in the past. They allow a differentiation of the sympathetic and parasympathetic activation, which are related to a low-frequency (LF) and a high-frequency (HF) component of the heart rate variability (HRV) signal, respectively. The resulting LF/HF ratio is a quantitative index of the sympatho-vagal balance. Sleep polygrams from 20 healthy volunteers were recorded in a sleep laboratory. Standard vegetative tests (orthostatic and Valsalva tests) were evaluated. A segmentation procedure, performed on the HRV signal, separated 70-130 transients during the night from the records of stationary heart rate fluctuations. From these periods the sympatho-vagal balance, quantified by the LF/HF, was computed by means of spectral analysis. The more synchronized the sleep was, the more the LF/HF decreased, whereas the LF/HF was significantly increased during REM sleep, indicating a sympathetic predominance during this period. Such an increase was also evident during the last 15 min before REM sleep onset. Results suggest that spectral analysis of the HRV provides additional information of the ultradian rhythmic behavior of the autonomic nervous system function beyond the traditional cardiovascular measurements (mean heart rate, blood pressure, etc.). In contrast to these measurements, which generally show a continuously decreasing cardiovascular activity, as the night proceeds, the results of this study reveal a high sympathetic peak activity during the later REM sleep periods, which is comparable in magnitude to that found in the upright position in wakefulness. This activity may be associated to the well-known incidence peak of ischemic events in the early morning hours.

Arousal↗

PubMed1989

Selection of a spectral analysis method for the assessment of velocity distribution based on the spectral distribution of ultrasonic Doppler signals.

The direct Fourier transform method, autoregressive modelling, the maximum likelihood method and the Wigner-Ville distribution were applied to the Doppler signal obtained from a fully insonated laminar model flow. The appreciation of the spectral method was based on the properties of the ratio variance/(fmean)2 (INT) of the spectrum. The basic criterion was the sensitivity of INT to the analysis parameters, especially the data window. The results of spectral analysis, as well as the properties of INT, were strongly affected by the method applied. The maximum likelihood method appeared best suited for the purpose of assessment of velocity distribution and is expected to give the best results in the case of in vivo blood flow. The performances of other discussed methods were inferior, due to their stronger incompatibility with the signal properties.

Blood Flow Velocity↗

PubMed1999

Evaluation of neurocardiac signals in pediatric patients with cyclic vomiting syndrome through power spectral analysis of heart rate variability.

OBJECTIVE: To investigate autonomic regulation of neurocardiac signals in pediatric patients with cyclic vomiting syndrome (CVS). METHODS: Fourteen patients with CVS, ages 3 to 16 years, were screened to eliminate any underlying cause for their symptoms, although 11 of the 14 patients had a history of migraine in the immediate family. Analysis of autonomic regulation was accomplished through power spectral analysis of the beat-to-beat heart rate variability signal. Data from affected patients were compared with data from 38 control subjects, ages 5 to 16 years, by a one-way analysis of variance. A measure of sympathovagal balance was obtained by computing a ratio of power in the low-frequency band (0. 02-0.15 Hz) to the power in the high-frequency band (0.15-0.4 Hz). RESULTS: Pediatric patients with CVS have an elevated sympathetic modulation of the sinus node as represented by the low frequency/high frequency ratio (1.45 +/- 0.42 in patients vs 0.89 +/- 0.29 in healthy control subjects, P <.001). CONCLUSIONS: The patients with CVS we studied have an autonomic imbalance with enhanced sympathetic and diminished parasympathetic vagal modulation of the heart.

Adolescent↗

PubMed1998

Functional mapping of human sensorimotor cortex with electrocorticographic spectral analysis. I. Alpha and beta event-related desynchronization.

Human scalp EEG studies have shown that event-related desynchronization (ERD) in the alpha (8-13 Hz) and beta (15-25 Hz) bands may be used to detect functional activation of sensorimotor cortex. However, in most previous studies somatotopy has not been examined in detail and brief, self-paced movements, focusing on the planning of motor output, have been used. We recorded electrocorticographic (ECoG) signals in five clinical subjects during a visual-motor decision task that was designed to activate the representations of different body parts in sensorimotor cortex. To focus more on execution of motor output than on its planning, subjects were instructed to make sustained isometric muscle contractions in different body parts (tongue protrusion, fist-clenching or foot dorsiflexion) in response to randomized visual stimuli depicting each action. ECoG spectral analysis utilized a mixed-effects analysis of variance model in which within-trial temporal dependencies were taken into account, and the magnitude and statistical significance of alpha and beta ERDs were mapped onto a surface rendering of each subject's brain MRI. Cortical electrical stimulation was performed in all subjects for clinical purposes, and the resulting maps of sensorimotor function were compared with those generated by ECoG spectral analysis. During the early phases of the motor responses, alpha ERD commonly occurred in a diffuse spatial pattern that was not somatotopically specific. During the late phases, the spatial pattern of alpha ERD usually became more focused and somatotopically specific. Maps of alpha ERD were closer to cortical stimulation maps when alpha ERD was sustained throughout the late phases of the motor responses. Thus, the topography of alpha ERD more resembled traditional somatotopy when its temporal profile approximated that of the motor response. The topography of beta ERD was often more discrete and somatotopically specific than that of alpha ERD, but beta ERD was often transient and sometimes absent. Sometimes, unilateral limb movement produced sustained alpha and beta ERD over bilateral sensorimotor cortices, with overlapping patterns for different body parts. The topographical spread of alpha ERD beyond expected functional-anatomical boundaries during early (and sometimes late) phases of motor responses invites a re-examination of traditional assumptions about sensorimotor functional neuroanatomy, as well as the role of alpha ERD as an index of cortical activation. We agree with others that the somatotopic representations of different body parts overlap more than previously thought. Also, unilateral limb movements may be associated with both contralateral and ipsilateral activation of sensorimotor cortex. We conjecture that alpha ERD may reflect activity within a broad synaptic network with distributed cortical representations.

Adult↗

PubMed1996

Power spectral analysis of spontaneous blood pressure and heart rate variability in elderly hypertensives.

To examine the influence of hypertension on cardiovascular variability in elderly subjects, we measured spontaneous beat-to-beat blood pressure (BPV) and heart rate variability (HRV) in elderly subjects with or without hypertension at rest and during tilting. The study group consisted of 23 community-dwelling, male elderly subjects (aged 62-75 years) and was divided into two groups, i.e., a hypertensive group (HT group; n = 11) and normotensive group (NT group; n = 12). According to the modeling and decomposing algorithm of an autoregressive process, we estimated the component power of low-frequency (LF; 0.03-0.15 Hz) and high-frequency components (HF; respiratory frequency) of BPV and HRV by power spectral analysis. We also measured plasma norepinephrine (PNE) levels in the two groups at rest and during tilting. In the HT group, we found that the amplitude of LF-BPV was greater (p < 0.05) and its relative change by postural tilting was smaller (p < 0.05) than those in the NT group. We found no significant difference in the amplitude of LF-HRV and HF-HRV between the two groups, and found no significant response of the amplitude of LF-HRV and HF-HRV to postural tilting. We also found no difference in PNE level between the two groups at rest or during tilting. These results suggest that the regulatory function of sympathetic vasomotor activity assessed by power spectral analysis of BPV is altered in hypertensive elderly subjects, although the influence of hypertension on the autonomic control of the heart is less dominant in the elderly.

Aged↗

PubMed1989

Spectral analysis on low frequency fluctuation in respiratory rhythm in the decerebrate cat.

Spectral analysis was performed on the fluctuation in respiratory intervals in vagotomized, paralyzed, and unanesthetized decerebrate cats. The respiratory interval was measured as the time interval between the onset of phrenic neural activity. When endtidal PCO2 was set at the same level as that before immobilization, the power spectral densities of the fluctuation in respiratory intervals were found to be inversely proportional to the frequency in the low frequency range of 0.001-0.1 Hz. All the tested animals showed this type of fluctuation (1/f fluctuation). In contrast, such characteristic 1/f fluctuation disappeared when the end-tidal PCo2 was raised to 50 or 60 mmHg. The spectral profile was almost flat in the frequency range of 0.001-0.1 Hz, i.e. similar to that of "white noise". This study demonstrated that the respiratory rhythm evaluated by phrenic neural discharges exhibited 1/f fluctuation and that the spectral characteristic of the fluctuation in respiratory intervals varied depending on the end-tidal PCo2.

Animals↗

PubMed2004

Determination of baroreceptor-stroke volume reflex sensitivity by power spectral analysis: a quantitative probe of baroreceptor-cardiac reflex.

Baroreceptor-cardiac reflex, which consists of baroreceptor-induced chronotropic and inotropic actions, is a very useful index of cardiac sympathovagal balance. Baroreceptor-heart rate reflex sensitivity, which reflects baroreceptor-induced chronotropic action, has been used as a marker of baroreceptor-cardiac reflex. However, it cannot be used in patients with chronotropic incompetence and/or implanted cardiac pacemaker. We hypothesized that baroreceptor-stroke volume (SV) reflex sensitivity, which reflects baroreceptor-induced inotropic action, may also be a useful method for measurement of baroreceptor-cardiac reflex, similar to the baroreceptor-heart rate reflex sensitivity. To test this hypothesis, we measured baroreceptor-SV reflex sensitivity expressed as ratio of low frequency (LF) power to total power of SV fluctuation (LF/TP(SV): %/mmHg) by spectral analysis of mean blood pressure and SV fluctuations, the gain in low-frequency band between two signals in supine and 60 degrees upright positions, and compared these values to baroreceptor-heart rate reflex sensitivity in 14 healthy subjects. Baroreceptor-SV reflex sensitivity correlated significantly with baroreceptor-heart rate reflex sensitivity (r = 0.73, p < 0.0001). In addition, baroreceptor-SV reflex sensitivity correlated significantly and positively with high frequency (HF) power (r = 0.57, p < 0.005) and negatively with LF/HF ratio (r = -0.57, p < 0.005) in power spectral analysis of R-R interval variability. Moreover, baroreceptor-SV reflex sensitivity in LF/TP(SV) correlated positively with the R-R interval (r = 0.70, p < 0.0001) and negatively with diastolic blood pressure (r = -0.50, p < 0.01). We conclude that baroreceptor-SV reflex sensitivity in LF/TP(SV) can be used as a quantitative probe of baroreceptor-cardiac reflex, similar to the baroreceptor-heart rate reflex sensitivity in healthy subjects, and it may enable us to estimate inotropic aspect in baroreceptor-cardiac reflex in patients with chronotropic incompetence and/or implanted pacemaker.

Adult↗

PubMed1992

Details of a real world implementation of Fourier techniques for power spectral analysis of heart rate variability.

A software package designed to perform a power spectral analysis of heart rate variability for Holter data is presented. The implementation is for the SpaceLabs Medical FT series 386/486-based Holter analysis workstation (Redmond, WA). The package is designed to allow rapid assessment of both short-term and long-term fluctuations in the heart rate spectrum. The package can be used to make a variety of spectral measurements of heart rate variability.

Electrocardiography, Ambulatory↗

PubMed1975

Spectral analysis of the EEG recorded during stimulation of the human fovea.

Computer spectral analysis was performed on the EEGs of 6 subjects recorded during monocular foveal stimulation. Stimulus wavelength and subjective brightness were varied independently to determine their importance to changes in the ongoing EEG. The contribution of oculomotor control to these effects and the retinal area of their origin were also investigated. The major results were as follows. (1) Stimulation of the fovea reduced the amplitude of the EEG and the coherence between hemispheres at all frequencies, but most dramatically in the alpha band. (2) It increased the variance of EEG amplitudes and widths of spectral peaks in the alpha band and shifted these peaks to lower frequencies. (3) Auto-spectral intensities in the alpha band were enhanced slightly at brightness levels near photopic threshold, but were unaffected by changes in stimulus wavelength. (4) The fovea appeared to be the most effective retinal area in which irradiation attenuated ongoing alpha activity.

Accommodation, Ocular↗

PubMed1997

Spectral analysis of systemic arterial pressure and heart rate signals as a prognostic tool for the prediction of patient outcome in the intensive care unit.

OBJECTIVES: To evaluate the applicability of changes in spectra of systemic arterial pressure and heart rate signals in the prediction of patient outcome in an adult intensive care unit (ICU). To compare the prognostic predictability of this method with the Acute Physiology and Chronic Health Evaluation II (APACHE II) scoring system. DESIGN: Prospective data collection from 52 ICU patients. SETTING: Adult ICU at a large, university-affiliated, medical center. PATIENTS: Consecutive patients who were admitted to the adult ICU due to noncardiac emergencies, and who remained for at least 2 days. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The demographic data, diagnosis, and survival data were recorded for each patient enrolled in this study. For the period between admission and 24 hrs before discharge, the APACHE II score was tabulated daily. Likewise, continuous, on-line, and real-time spectral analysis of systemic arterial pressure and heart rate signals was carried out every day for at least 30 mins at 2200 to 2400 hrs. The averaged power density values during this 30-min recording period of the high-frequency (0.15 to 0.4 Hz), low-frequency (0.08 to 0.15 Hz), and very low-frequency (0.016 to 0.08 Hz) components of systemic arterial pressure and heart rate signals were subsequently computed. Systemic vascular resistance index and cardiac index were also determined daily. We observed a trend of changes in the spectral components of systemic arterial pressure and heart rate signals in patients who eventually survived (n = 25) or died (n = 27). Progressive increases in the power density values of both the low-frequency and very low-frequency components of systemic arterial pressure and heart rate signals appeared to be related to recovery. Conversely, progressive decreases in the power density values of these spectral components was indicative of deterioration and fatality. The predicted outcome based on the trend of changes in the low-frequency and very low-frequency components of systemic arterial pressure and heart rate signals correlated positively with daily APACHE II scores. No direct correlation, however, was indicated by mean systemic arterial pressure, heart rate, systemic vascular resistance index, and cardiac index. We also confirmed that the differential trend of spectral changes in patients who survived or died was not due to circadian rhythm, nor alterations in the responsiveness of the blood vessels to intravenous infusion of dopamine. CONCLUSION: Power spectral analysis of systemic arterial pressure and heart rate signals offers a reasonable means of monitoring acute, critically ill patients, and may be used as an alternative prognostic tool for the prediction of patient outcome in the ICU.

APACHE↗

PubMed1995

Assessment of autonomic function in myotonic dystrophy 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 10 myotonic dystrophy (MD) patients (4 men and 6 women, aged 37-53 years) and 10 age- and sex-matched healthy, sedentary humans (control) at rest in the supine position. All MD patients had no cardiac conduction disturbances (i.e., atrioventricular or intraventricular conduction defects) on 12-lead electrocardiogram and were able to walk and perform daily activities. In the MD group, the total power, the power of the low-frequency component (a marker of sympathetic and vagal modulation of heart rate) and that of the high-frequency component (a marker of vagal modulation of heart rate) were smaller than those in the control group (P < 0.01, P < 0.05 and P < 0.05, respectively). The results of this study suggest that the cardiovascular autonomic nervous system contributing to the HRV may be disturbed even in the MD patients who can walk and perform daily activities. Therefore, one must give careful consideration to the cardiovascular autonomic dysfunction, as well as the cardiac conduction disturbance in the MD patients.

Adult↗