Characteristics of electroencephalogram signatures in sedated patients induced by various anesthetic agents

Devices that monitor the depth of hypnosis based on the electroencephalogram (EEG) have long been commercialized, and clinicians use these to titrate the dosage of hypnotic agents. However, these have not yet been accepted as standard monitoring devices for anesthesiology. The primary reason is that the use of these monitoring devices does not completely prevent awareness during surgery, and the development of these devices has not taken into account the neurophysiological mechanisms of hypnotic agents, thus making it possible to show different levels of unconsciousness in the same brain status. An alternative is to monitor EEGs that are not signal processed with numerical values presented by these monitoring devices. Several studies have reported that power spectral analysis alone can distinguish the effects of different hypnotic agents on consciousness changes. This paper introduces the basic concept of power spectral analysis and introduces the EEG characteristics of various hypnotic agents that are used in sedation.

Neuropeptides in the posterodorsal medial amygdala modulate central cardiovascular reflex responses in awake male rats

The rat posterodorsal medial amygdala (MePD) links emotionally charged sensory stimuli to social behavior, and is part of the supramedullary control of the cardiovascular system. We studied the effects of microinjections of neuroactive peptides markedly found in the MePD, namely oxytocin (OT, 10 ng and 25 pg; n=6/group), somatostatin (SST, 1 and 0.05 μM; n=8 and 5, respectively), and angiotensin II (Ang II, 50 pmol and 50 fmol; n=7/group), on basal cardiovascular activity and on baroreflex- and chemoreflex-mediated responses in awake adult male rats. Power spectral and symbolic analyses were applied to pulse interval and systolic arterial pressure series to identify centrally mediated sympathetic/parasympathetic components in the heart rate variability (HRV) and arterial pressure variability (APV). No microinjected substance affected basal parameters. On the other hand, compared with the control data (saline, 0.3 µL; n=7), OT (10 ng) decreased mean AP (MAP50) after baroreflex stimulation and increased both the mean AP response after chemoreflex activation and the high-frequency component of the HRV. OT (25 pg) increased overall HRV but did not affect any parameter of the symbolic analysis. SST (1 μM) decreased MAP50, and SST (0.05 μM) enhanced the sympathovagal cardiac index. Both doses of SST increased HRV and its low-frequency component. Ang II (50 pmol) increased HRV and reduced the two unlike variations pattern of the symbolic analysis (P<0.05 in all cases). These results demonstrate neuropeptidergic actions in the MePD for both the increase in the range of the cardiovascular reflex responses and the involvement of the central sympathetic and parasympathetic systems on HRV and APV.

Association between Autonomic Nervous Activities of Climacteric Patients and Undefined Symptoms / 日本東洋医学雑誌

This study was designed to investigate the association between autonomic nervous activities and clinical symptoms of climacteric women with qi disturbance. Power spectral analysis of heart-rate variability (HRV) was performed in 55 climacteric patients with undefined symptoms (age;51.9±2.8). The total power of HRV in patients with hot flushes was significantly higher (529.6±529.9ms2) than that of patients without this symptom (295.4±260.8 ms2) (P<0.05). The sympathetic nerve system (SNS) index in patients with hot flushes and with jitters (2.81±2.93 and 3.16±2.78), was significantly higher than those of patients without them (1.03±0.78 and 0.87±0.72) (P<0.001 and P<0.0001, respectively). The parasympathetic nerve system (PNS) index of patients with hot flushes and patients with jitters (0.38±0.19 and 0.33±0.16) was significantly lower than those of patients without them (0.55±0.17 and 0.58±0.14) (P<0.001 and P<0.0001, respectively). These findings indicate that HRV-based assessment of the autonomic nervous system activity of climacteric women with hot flushes and jitters, which have been known as symptoms of qi counterflow in the Kampo medicine, is associated with an increase in sympathetic nerve system and a decrease in parasympathetic nerve system activity. It has been suggested that autonomic nervous activities be included in the part of pathological condition of qi in the Kampo medicine, and that evaluation of qi be used as one diagnostic tool in the practical Kampo medicine, or fusion of western and oriental medicine.

Differences between Physostigmine- and Yohimbine-induced States Are Visualized in Canonical Space Constructed from EEG during Natural Sleep-wake Cycle in Rats

Although quantitative EEG parameters, such as spectral band powers, are sensitive to centrally acting drugs in dose- and time-related manners, changes of the EEG parameters are redundant. It is desirable to reduce multiple EEG parameters to a few components that can be manageable in a real space as well as be considered as parameters representing drug effects. We calculated factor loadings from normalized values of eight relative band powers (powers of 0.5, 1.0~2.0, 2.5~4.0, 4.5~5.5, 6.0~8.0, 8.5~12.0, 12.5~24.5, and 25~49.5 Hz bands expressed as ratios of the power of 0.5-49.5 Hz band) of EEG during pre-drug periods (11:00~12:00) by factor analysis and constructed a two-dimensional canonical space (reference canonical space) by canonical correlation analysis. Eight relative band powers of EEG produced by either physostigmine or yohimbine were reduced to two canonical scores in the reference canonical space. While changes of the band powers produced by physostigmine and yohimbine were too redundant to describe the difference between two drugs, locations of two drugs in the reference canonical space represented the difference between two drug's effects on EEG. Because the distance between two locations in the canonical space (Mahalanobis distance) indicates the magnitude of difference between two different sets of EEG parameters statistically, the canonical scores and the distance may be used to quantitatively and qualitatively describe the dose-dependent and time-dependent effects and also tell similarity and dissimilarity among effects. Then, the combination of power spectral analysis and statistical analysis may help to classify actions of centrally acting drugs.

Reproducibility of heart rate variability parameters measured in healthy subjects at rest and after a postural change maneuver

Heart rate variability (HRV) provides important information about cardiac autonomic modulation. Since it is a noninvasive and inexpensive method, HRV has been used to evaluate several parameters of cardiovascular health. However, the internal reproducibility of this method has been challenged in some studies. Our aim was to determine the intra-individual reproducibility of HRV parameters in short-term recordings obtained in supine and orthostatic positions. Electrocardiographic (ECG) recordings were obtained from 30 healthy subjects (20-49 years, 14 men) using a digital apparatus (sampling ratio = 250 Hz). ECG was recorded for 10 min in the supine position and for 10 min in the orthostatic position. The procedure was repeated 2-3 h later. Time and frequency domain analyses were performed. Frequency domain included low (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) bands. Power spectral analysis was performed by the autoregressive method and model order was set at 16. Intra-subject agreement was assessed by linear regression analysis, test of difference in variances and limits of agreement. Most HRV measures (pNN50, RMSSD, LF, HF, and LF/HF ratio) were reproducible independent of body position. Better correlation indexes (r > 0.6) were obtained in the orthostatic position. Bland-Altman plots revealed that most values were inside the agreement limits, indicating concordance between measures. Only SDNN and NNv in the supine position were not reproducible. Our results showed reproducibility of HRV parameters when recorded in the same individual with a short time between two exams. The increased sympathetic activity occurring in the orthostatic position probably facilitates reproducibility of the HRV indexes.

Power Spectral Analysis of Heart Rate Variability in Adolescent Male Athletes.

Background: Cardiac autonomic nervous activities (CANA) deteriorate with age, obesity, sedentary life style and in various cardiac and noncardiac disease conditions. Regular physical exercise may improve CANA in health and diseases. Power spectral analysis (PSA) of Heart rate variability (HRV) is one of the most promising newer techniques to quantify CANA. Objective: To analyze HRV by Power Spectral method in order to find out the influence of regular physical exercise on CANA in male adolescent athletes. Method: This cross sectional study was carried out on 62 adolescent male athletes aged 12-18 years (group B), in the Department of Physiology, Bangabandhu Sheikh Mujib Medical University from 1st July 2007 to 30th June 2008. For comparison, 30 age, sex, BMI and socioeconomic condition matched apparently healthy sedentary subjects (group A) were also studied. The study subjects were selected from the BKSP (Bangladesh Krira Shikka Prothistan, Savar, Dhaka) and the control from a residential school of Dhaka city.Power spectral measures of HRV including Total Power (TP), Very Low Frequency Power (VLF) Low Frequency(LF), High Frequency (HF) LF/HF were measured by a Polygraph . For statistical analysis, Idependent-Sample t-test was used. Results: Total power, HFnu power and the VLF,LF,HF were significantly (P<0.001) higher and LFnu power and the LF/HF ratio were significantly (P<0.001) lower in athletes than those of nonathletes which indicate higher cardiac parasympathetic and lower sympathetic activity in athletes. Conclusion: Cardiac Autonomic regulation with increased parasympathetic and decreased sympathetic modulation may occur with in athletes engaged with regular physical exercise.

Heart Rate Variability during Propofol-Remifentanil TCI Induction in Diabetic Patients / 대한마취과학회지

BACKGROUND: The aim of this study was to compare heart rate variability (HRV) changes between diabetics and non-diabetics throughout induction with maintaining BIS 40-60 by propofol-remifentanil target controlled infusion. METHODS: Non-diabetic patients (n = 12) and non-insulin dependent diabetes mellitus (NIDDM) patients (n=12) were recruited. Anesthesia was induced by target controlled infusion of propofol and remifentanil. Target effect-site concentration of propofol was adjusted to maintain bispectral index (BIS) 40-60, and target effect-site concentration of remifentanil was adjusted to maintain blood pressure (BP) within 20% of baseline value. The HRV was recorded at resting, after glycopyrrolate injection, during BIS 40-60, and after intubation. Log-transformed power spectrum (ms2) of TP (total power, < or = 0.4 Hz), LF (low frequency, 0.04-0.15 Hz), HF (high frequency, 0.15-0.4 Hz), LFnorm (normalized LF, LF/[LF + HF]), HFnorm (normalized HF, HF/[LF + HF]), and LF/HF ratio were compared. RESULTS: Initial LnTP, LnLF, and LnHF was significantly lower in diabetics (P < 0.05). During BIS 40-60, LnTP, LnLF, and LnHF in non-diabetics decreased significantly (P < 0.05). Immediately after intubation, LnLF, LnHF in non-diabetics, and LnHF in diabetics decreased significantly (P < 0.05). LF/HF ratio showed no significant change throughout induction. Systolic, diastolic BP, mean arterial pressure, and heart rate have no significant differences between the groups. CONCLUSIONS: This study suggests that hemodynamic variables and balance of autonomic nervous system measured by HRV can not be altered during induction, by adjusting effect site concentration of propofol and remifentanil in accordance with BIS and BP in diabetic patients.

Differential Effects of Typical and Atypical Antipsychotics on MK- 801-induced EEG Changes in Rats

We examined whether the abnormal EEG state by NMDA receptor blocker MK-801 can be reversed by typical and atypical antipsychotics differentially by comparing their spectral profiles after drug treatment in rats. The spectral profiles produced by typical antipsychotics chlorpromazine (5 mg/kg, i.p.) and haloperidol (0.5 mg/kg, i.p.) were differ from that by atypical antipsychotic clozapine (5 mg/kg, i.p.) in the rats treated with or without MK-801 treatment (0.2 mg/kg, i.p.) which produce behavioral abnormalities like hyperlocomotion and stereotypy. The dissimilarity between the states produced by antipsychotics and the control state was examined with the distance of the location of the canonical variables calculated by stepwise discriminant analysis with the relative band powers as input variables. Although clozapine produced more different state from normal state than typical antipsychotics, clozapine could reverse the abnormal schizophrenic state induced by MK-801 to the state closer to the normal state than the typical antipsychotics. The results suggest that atypical anesthetic can reverse the abnormal schizophrenic state with negative symptom to the normal state better than typical antipsychotic. The results indicate that the multivariate discriminant analysis using the spectral parameters can help differentiate the antipsychotics with different actions.

The Influence of Sevoflurane on the Autonomic Nervous System / 대한마취과학회지

BACKGROUND: Sevoflurane is a new inhalation anesthetic, which shows stable hemodynamic features, and does not have a pungent odor, so that it can be used as an inhalational induction agent. But mask ventilation can make patients anxious, and can stimulate the sympathetic nervous system. Therefore, we evaluated the effect of midazolam administered right before inhalation induction with sevoflurane on the autonomic nervous system using power spectral analysis. METHODS: We studied 28 patients undergoing elective surgery. They were assigned to one of two groups to receive either sevoflurane with midazloam (M group) or sevoflurane alone (S group). Anesthesia was induced with 6% sevoflurane and 0.03 mg/kg midazolam or 6% sevoflurane alone. Midazolam was administered immediately before induction with sevoflurane. An electrocardiogram was applied to all patients and connected to a computer, for power spectral analysis. Power values were recorded on arrival, pre-intubation, post-intubation and pre-incision, and compared between two groups. RESULTS: Power values at low frequency were lower, and the time to loss of eye lash reflex and induction were shorter in the M group than in the S group. CONCLUSIONS: The administration of midazolam before induction with sevoflurane reduced the activity of the sympathetic nervous system versus induction with sevoflurane alone.

Spectral Analysis of Heart Rate Variability during General Anesthesia in Diabetes Mellitus Patients / 대한마취과학회지

BACKGROUND: This study was undertaken to elucidate the effects of general anesthesia by power spectral analysis of heart rate variability in diabetic and non-diabetic patients. METHODS: EKG was measured in 35 patients, 17 without diabetes (control group) and 18 with diabetes (DM group). EKG and signal were digitized at 500 Hz for; 3 min in the period before anesthesia, during 1 to 5 min after intubation, 5 to 10 min after intubation and 30 min after skin incision. We also measured systolic and diastolic blood pressure, and heart rate in each period. The signal was analyzed using a fast Fourier transform algorithm to yield the power spectrum of the heart rate variability. Low frequency (LF, 0.04-0.15 Hz), high frequency (HF, 0.15-0.5 Hz) powers and the LF/HF ratio were obtained. RESULTS: The blood pressure was increased transiently by tracheal intubation but decreased gradually while anesthesia progressed. To maintain a minimal pressure range, ephedrine 10mg was injected into 11 patients in the DM group. Heart rate also showed the same trend as blood pressure, and no difference between the two groups. LF and HF power of heart rate variability, which was measured before induction, were significantly decreased in the DM group compared to the control group. As anesthesia was applied, overall frequency power was significantly attenuated in both groups. As the operation proceeded, frequency power gradually recovered only in the control group. Changes of the LF/HF ratio in the control group were 2.58+/-0.62 at pre-induction and 5.47+/-1.36, 1.11+/-0.33, 1.03+/-0.21 successively and in the DM group were 3.21+/-0.76 at pre-induction and 4.92+/-2.55, 0.80+/-0.18, 0.56+/-0.16 as the anesthesia progressed. CONCLUSIONS: These results suggest that the heart rate variability is significantly attenuated when anesthetics are administered, and that in the DM group heart rate variability is more prominently attenuated than in the control group. This result implies that diabetic patients have an underlying impairment of autonomic nervous system function and that this may lead to a further impairment of autonomic control, which has the potential to allow substantial intraoperative blood pressure liability during periods of surgical stress or blood loss.

RELATIONSHIP BETWEEN HEART RATE VARIABILITY DURING EXERCISE AND VENTILATORY THRESHOLD / 体力科学

The aim of this study was to investigate the relationship between heart rate variability (HRV) during exercise and ventilatory threshold (VT), using the MemCalc system which is superior in spectral analysis. Nine healthy male subjects with no cardiopulmonary disease performed an exercise test to exhaustion to determine VT on a bicycle ergometer. Low frequency (LF : 0.04-0.15 Hz), high frequency (HF : 0.15-0.40Hz) and LF/HF ratio power spectra were calculated by maximum entropy method (MEM) spectral analysis, using the MemCalc system. In each case, when the subject started exercise, the HF component declined rapidly during the first 30 seconds ; and compared to the resting value, it declined to approximately 5 % at VT. The possibility of using this phenomenon as a criterion for setting intensity of exercise is tinder consideration. The LF/HF ratio showed different patterns of variation among the subjects. A significant linear relationship was seen between the declining rate of the HF component and VT (r=0.93, p<0.001), suggesting a corres pondence between the heart's capability of adjusting to maintained exercise and high endurance capacity.

Determinants of Heart Rate Variability in General Korean Population

BACKGROUND AND OBJECTIVES: Heart rate variability has been known to be a prognostic factor of heart disease. However, determinants of heart rate variability in general korean population without clinical heart disease have not been studied. Objectives of this study were to measure heart rate variability in general population and to investigate clinical determinants of heart rate variability. METHODS:Heart rate variability measures were obtained by LRR-03TM and MemCalcTM software (GMS, Tokyo, Japan) from public officials in a district of Seoul and their families(n=69). Predictors of heart rate variability included age, gender, heart rate, smoking status, systolic blood pressure, diastolic blood pressure, serum total cholesterol, HDL-cholesterol. Univariate analysis and analysis of variance of low frequency power(0.04-0.15 Hz), high frequency power(0.15-0.30 Hz), and total power spectrum in relation to explanatory variables were done. In order to select determinants of heart rate variability, multiple linear regression model of each heart rate variability measure was created and stepwise selection method was applied. RESULTS: Analysis of variance showed that older age, higher heart rate, body mass index > or =27, systolic blood pressure > or =140 mmHg, diastolic blood pressure > or =90 mmHg, and serum total cholesterol > or =240 mg/dl were negatively associated with one or more heart rate variability measures. Serum HDL-cholesterol > or =35 mg/dl was positively associated with low and high frequency power. Multiple linear regression analyses showed that age and heart rate were the major determinants, gender and cardiovascular risk factors such as diastolic blood pressure, HDL-cholesterol, and smoking contributed to one or more heart rate variability measures. CONCLUSIONS: Age, heart rate, gender, and cardiovascular risk factors must be considered when evaluating heart rate variability.

Development of Data Acquisition System for Quantification of Autonomic Nervous System Activity and It's Clinic Use / 영남의대학술지

BACKGROUND: Power spectrum analysis method is a powerful noninvasive tool for quantifying autonomic nervous system activity. In this paper, we developed a data acquistion system for estimating the activity of the autonomic nervous system by the analysis of heart rate and respiratory rate variability using power spectrum analysis. MATERIALS AND METHODS: For the detection of QRS peak and measurement of respiratory rate from patient's ECG, we used low-pass filter and impedence method respectively. This system adopt an isolated power for patient's safety. In this system, two output signnals can be obtained: R-R interval(heart rate) and respiration rate time series. Experimental ranges are 30-240 BPM for ECG and 15-80 BPM for respiration. RESULTS: The system can acquire two signals accurately both in the experimental test using simulator and in real clinical setting. CONCLUSION: The system developed in this paper if efficient for the acquisition of heart rate and respiration signals. The system will play a role in research area for improving our understanding of the pathophysiologic involvement of the autonomic nervous system in various disease states.

Spectral Analysis of Fetal Heart Rate Variability in Fetal Distress / 대한산부인과학회잡지

OBJECTIVE: To evaluate the usefulness of power spectral analysis on fetal heart rate variability as a new diagnostic method of fetal distress. STUDY DESIGN: Among 76 pregnant women who underwent computerized electronic fetal monitoring and cord blood gas analysis, we divided them into 3 groups, i.e.; normal fetus group (36), presumed distress group (26) and acidemic distress group (14). In order to perform linear analysis on the raw data of the fetal heart rate, after resampling, we performed Fourier transformation and investigated power distributions among very low frequency (VLF), low frequency (LF), high frequency (HF) bands, and autonomic balance (LF/HF). RESULTS: The results of the spectral analysis showed that in normal fetus group, the difference in the distribution of power spectrums of VLF, LF and HF was significantly higher than in presumed distress group and acidemic distress group. In fetal distress, the LF and VLF value (0.0023, 0.0437) were good predictors (sensitivity 97.5%, 75.0% and specificity 86.1%, 94.4%). The LF value (0.0013) was a good predictor in fetal acidemia (sensitivity 97.5% and specificity 86.1%). CONCLUSIONS: A computerized spectral analysis of fetal heart rate variation is a good predictor of fetal distress, which is made automatically and objectively.

Effects of endurance training and detraining on cardiac autonomic nervous system activity in young males / 体力科学

The effects of endurance training and detraining on cardiac autonomic nervous system activity were studied by using the power spectral analysis of heart rate (HR) variability. Twenty-one sedentary male subjects were trained for 8 weeks using cycle ergometer exercise [70% of maximal oxygen uptake (VO<SUB>2</SUB>max), 60 min, 3.4 times/wk] . Resting HR for 5 min was recorded before the training, after the 8-week training period, and after the 2-week and 4-week detraining period. The indices of cardiac parasympathetic and sympathetic nervous system activity were determined by Mem-Calc method, as the high frequency power (HF : 0.15-0.50 Hz) and the ratio of the low frequency power (LF : 0.04-0.15 Hz) to the HF (LF/HF), respectively. The VO<SUB>2</SUB>max after the training and 4 weeks detraining period were significantly higher than the initial value (before training : 41 ± 1 ml/kg/min ; after training: 48±2, <I>P</I><0.0001; after detraining: 46±2, <I>P</I><0.001) . The HF was significantly in-creased by the training (<I>P</I><0.05), and maintained the increased level for the 2-week detraining period (before training : 6.4±0.3 In ms<SUP>2</SUP>; after training: 7.0±0.2, <I>P</I><0.01; after 2-week detrain-ing: 7.0±0.2, <I>P</I><0.05) . The increase in the HF, however, disappeared after the 4-week detraining period (6.8±0.31n ms<SUP>2</SUP>) . The LF/HF did not show any significant changes during the training and detraining period. These results suggest that an endurance exercise with moderate intensity enhan-ces cardiac parasympathetic nervous system activity, but not cardiac sympathetic nervous system activity. The enhanced cardiac parasympathetic nervous system activity, however, may regress rapidly during detraining period.

QEEG Findings in Attention Deficit/Hyperactivity Disorder / 신경정신의학

OBJECTIVE: To find out the distinctive topographic EEG profiles of subject with attention deficit hyperactivity disorder comparing with age & sex matched control. METHOD: The quantitative electroencephalographies(QEEGs) of 20 drug-naive ADHD patients without any other psychiatric diagnosis were analyzed and compared to age and sex-matched controls using spectral analysis. RESULTS: 1) Slow waves(delta and theta) bipolar relative powers of the diverse areas in both hemispheres increased in drug-free ADHD patients, compared to controls. 2) Delta and theta bipolar relative powers of localized centro-temporal areas in left hemispheres increased in drug-free ADHD patients compared to controls. 3) Interhemispheric coherence and asymmetry are increased in diverse areas in ADHD patient compared to controls. CONCLUSION: We confirmed QEEG abnormalities in pure ADHD patients, especially in frontal and parietal areas. These results are compatible with other structural and functional imaging studies of ADHD.

The Effects of Intravenous Insulin on Hemodynamics and Autonomic Nervous System Activity in Anesthetized Dogs / 대한마취과학회지

BACKGROUND: Even though the cardiovascular actions of insulin were first described shortly after introduction into clinical practice, the precise physiological role and mechanism of insulin-mediated cardiovascular actions are not known. The aim of the present study was to investigate the changes in hemodynamics after an insulin injection and the role of the autonomic nervous system in mediating the responses to insulin. METHODS: Nine mongrel dogs of the male sex, weighing 20 - 26 kg, were studied. Anesthesia was maintained with pentobarbital and vecuronium after the administration of the loading dose. Femoral and pulmonary artery catheters were placed for obtaining blood samples (ABGA, electrolytes, glucose and plasma catecholamines) and measuring hemodynamic variables. Real time power spectral analysis of R-R interval variability was displayed on the color power spectrum every 30 seconds by a simple connection between the EKG monitor and computer via an A/D converter. After control values were obtained, porcine insulin was administrated intravenously as a bolus injection (2 U/kg). Blood glucose and potassium were maintained within physiological range by simultaneous infusion of 50% glucose (2-4 ml/kg/h) and potassium (0.5-1.0 mEq/kg/h). Parameters were measured respectively in 9 steps; 10min before insulin injection (control), 1, 5, 10, 20, 30, 40, 50 and 60min after insulin injection. RESULTS: Heart rate, mean arterial blood pressure and cardiac output increased and systemic vascular resistance decreased significantly after the insulin injection. No significant changes in plasma norepinephrine and epinephrine levels could be detected. Power spectral density of low frequency and ratio oflow and middle frequency power to high frequency power increased significantly 1min after insulin injection but did not increase thereafter. High frequency power remained significantly below the control value after the insulin injection. CONCLUSIONS: Although catecholamine concentration itself did not show a significant change, PSA data reveals that insulin may exert a stimulatory action on the sympathetic nervous system and a depressive action on the parasympathetic nervous system independent of hypoglycemia immediately after an insulin injection and insulin-induced vasodilation is not related to the autonomic nervous system.

Autonomic Nervous Response to Cold Provocation in Vibration-Induced White Finger(VWF) Patients with HRV Analysis / 航天医学与医学工程

Objective To evaluate the autonomic nervous response of Vibration-induced white finger(VWF) patients to cold provocation test by power spectral analysis of heart rate variability(HRV).Methods The cold provocation test was conducted in 22 VWF patients and 19 healthy volunteers.ECG was recorded during the experiment,and converted to R-R interval signals after the experiment.The normalized LF[(0.02～0.15) Hz]component power,normalized HF[(0.15～0.40) Hz] component power and the ratio of LF to HF power(LF/HF ratio) were calculated.Results At the beginning of cold exposure,there were a significant decrease of HF% in both groups,and a significant increase of LF/HF ratio in VWF group as compared with pre-exposure value.The LF/HF ratio in VWF group during cold exposure was significantly higher than that in the control group.Conclusion Cold stimuli induced depression of parasympathetic nervous system in both groups,and the sympatho-vagal balance was maintained in the control group,but in VWF group it became sympathetic dominance during cold exposure.The sympathetic nervous system of VWF patients may be hyperreactive to cold stimuli.

Spectral Analysis of Heart Rate and Blood Pressure Variability during Hemorrhage in Propofol-Anesthetized Rats / 대한마취과학회지

BACKGROUND: This study was aimed to elucidate the effect of propofol anesthesia on circulatory response to hemorrhage in rats by power spectral analysis of heart rate and blood pressure variability. METHODS: Nineteen male Sprague-Dawley rats weighing 350-580 g were divided into propofol (2 mg/kg, iv)-anesthetized (P, n=10) and saline control (C, n=9) groups. Blood pressure signal was digitized at 500 Hz for 5 min at basal, during hemorrhage and after hemorrhage. The signal was analyzed with fast Fourier transform algorithm to yield power spectra of systolic (SPV) and diastolic (DPV) blood pressure and cycle length variability (HRV). Very low frequency (VLF, 0.02-0.26 Hz), low frequency (LF, 0.26-0.75 Hz), high frequency (HF, 0.75-5.00 Hz) powers, LF/HF ratio and total power were obtained. Powers of each band were expressed as percent of total power. RESULTS: Blood pressure was decreased during hemorrhage in C and with a greater magnitude in P. Heart rate tended to increase during hemorrhage in C, but was not changed in P. LF powers of SPV in P was decreased after propofol injection. Hemorrhage decreased LF and increased HF. LF powers of DPV in P was decreased after propofol injection. Hemorrhage caused a further decrease in LF. LF powers of HRV in P was decreased after propofol injection. Hemorrhage caused a further decrease in LF. Powers of SPV, DPV and HRV in C were not changed by hemorrhage. LF/HF of SPV, DPV and HRV were decreased during hemorrhage in P, but not in C. CONCLUSIONS: These results suggest that propofol depressed sympathetic activity to diminish peripheral vascular tone and hemorrhage under propofol anesthesia resulted in a greater blood pressure fall due to impaired sympathetic compensation including attenuated baroreflex mechanism.

Assessment of Autonomic Function in Stroke Patients by Power Spectral Analysis of Heart Rate Variability

OBJECTIVE: To evaluate the effects of orthostatic stress with a head-up tilt on the autonomic nervous system and to determine how a cerebral stroke influences the cardiac autonomic function, using the power spectral analysis(PSA) of heart rate variability(HRV). METHOD: We studied 11 stroke patients with a left hemiplegia and 14 patients with a right hemiplegia. Their hemispheric brain lesions were confirmed by the MRI. The ECG and respiration signals were recorded at the tilt angle of 0o and 70o for 5 minutes under the condition of frequency controlled respirtaion(0.25 Hz). Data were compared with the age- and sex-matched 12 healthy controls. RESULT: In a control group, the normalized high frequency power showed a significant decrease during the head-up tilt(p0.05). Compared with the right hemiplegia and control groups, the left hemiplegia group was associated more with a reduced low and high frequency power and showed no significant changes under the orthostatic stress. CONCLUSION: PSA of HRV can identify the reduced cardiac autonomic activity in stroke patients, with a greater reduction in the left hemiplegia group than in the right hemiplegia group, which may cause a high risk of cardiac arrhythmias and sudden death.