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At least 1,009 records · Page 56Linked to original sources

PubMed2002

The effects of cold-water immersion on power output and heart rate in elite cyclists.

The purpose of this study was to examine the effects of cold-water immersion on power output, heart rate, and time to peak power in 10 well-trained cyclists. The Compu-trainer Professional Model 8001 computerized stationary trainer was used to evaluate maximum power, average power, and time to peak power during a simulated cycling sprint. The heart rate was measured using a Polar heart rate monitor. Subjects performed 2 maximum-effort sprints (for approximately 30 seconds) separated by either an experimental condition (15 minutes of cold-water immersion at 12 degrees C up to the level of the iliac crest) or a control condition (15 minutes of quiet sitting). All subjects participated under both control and experimental conditions in a counterbalanced design in which 5 subjects performed the experimental condition first and the other 5 subjects performed the control condition first. Each condition was separated by at least 2 days. The time to peak power was not different between the 2 conditions. Maximum and average powers declined by 13.7 and 9.5% for the experimental condition but only by 4.7 and 2.3% for the control condition, respectively. The results also demonstrated a significantly greater decline in maximum heart rate after cold-water immersion (8.1%) than under the control condition (2.4%). Average heart rate showed a decrease of 4.2% under the experimental condition, as compared with an increase of 1.5% under the control condition. The major findings of this study suggest that a relatively brief period of cold-water immersion can manifest significant physiological effects that can impair cycling performance.

Adult↗

PubMed2002

The effectiveness of two different battery-powered toothbrushes on whitening through removal of stain.

Whitening dentifrices have recently become popular, achieving a whitening benefit by surface chemical action and/or abrasion that serve to remove extrinsic stains and/or prevent extrinsic stain buildup. Some powered toothbrushes have also been demonstrated to have whitening/stain-removal efficacy when used with standard dentifrice products. The objective of this study was to evaluate the effectiveness of an experimental prototype powered toothbrush (Crest SpinBrush Pro) and a commercially available powered toothbrush (Crest SpinBrush) on dental whitening through the removal of extrinsic stain. This study was a randomized, controlled, examiner-blind, parallel-group design, which examined extrinsic stain removal over four weeks of brushing by 70 subjects. Following a three-week period of stain induction using rinses of chlorhexidine and tea, subjects were randomized to use one of the two toothbrushes. Tooth stain was scored using the Lobene stain index at baseline, and after two and four weeks of toothbrush use. Prior to statistical analysis, the stain scores were averaged on a per-subject basis. The stain reductions (baseline minus post-treatment) in average scores were calculated and analyzed using an analysis of covariance, with baseline average score as the covariate. The experimental prototype powered toothbrush (Crest SpinBrush Pro) delivered statistically significant (p < 0.001) adjusted (via analysis of covariance) mean reductions from baseline in Lobene composite stain scores of 1.90 and 2.11 after 2 weeks and 4 weeks of use, respectively. These results represent 56-62% reductions in extrinsic stain compared to baseline. The commercially available powered toothbrush (Crest SpinBrush) also delivered statistically significant (p < 0.001) adjusted (via analysis of covariance) mean reductions from baseline in Lobene composite stain scores, with magnitudes of 1.95 and 2.22 after two and four weeks of use, respectively. These results represent 60-68% reductions in extrinsic stain compared to baseline. In conclusion, both the experimental prototype powered toothbrush and the commercially available powered toothbrush were effective in removing extrinsic tooth stain.

Adult↗

PubMed2000

[An experiment on disinfection using high power microwave].

This experimental disinfection was intended to examine the effect of high power microwave on bacteria, and the putative nonthermal effect. The bacteria of the experimental groups were irradiated by high power microwave in different intensities and time and were compared with the controls--bacteria heated only. The principles of disinfection by means of high power microwave were studied. The results showed that the temperature did not change after the dry bacteria were irradiated by high power microwave in different intensities and time, but the number of bacteria alive decreased significantly(P < 0.05). The high power microwave's effect of disinfection was greater in the wet bacteria group than in the dry bacteria group and the bacteria heated group. These data indicate that the disinfection effect of high power microwave is higher than that of heating. High power microwave can kill dry bacteria, and it has the nonthermal effect in addition to its thermal effect.

Disinfection↗

PubMedDate not supplied

Optimal laser power to rupture Bruch's membrane and the retinal vein in the pig.

BACKGROUND AND OBJECTIVE: For laser-induced chorioretinal venous anastomosis to become a viable treatment option for perfused central retinal vein occlusion, laser parameters must be refined to more reliably create venous anastomoses while minimizing complications. The aim of this study was to determine the lowest argon laser power at which Bruch's membrane and the retinal vein are ruptured in 100% of attempts in the porcine eye. MATERIALS AND METHODS: Testing was performed on 6 eyes of 3 Yorkshire Cross pigs, using an argon green laser. The spot size was 50 microm and the duration was 0.2 seconds for all applications. Twelve laser powers were tested, from 0.5 to 6 W, increasing by increments of 0.5 W. Light microscopy was used to determine the frequency of rupture of Bruch's membrane and the retinal vein for each power. RESULTS: The rupture rate of Bruch's membrane was 0% at 0.5 W, 5% at 1.0 W, 20% at 1.5 W, 70% at 2.0 W, and 100% for all powers from 2.5 to 6.0 W. The rupture rate of the retinal vein was 0% at 0.5 W, 5% at 1.0 W, 30% at 1.5 W, 60% at 2.0 W, 80% at 2.5 W, and 100% for all powers from 3.0 to 6.0 W. CONCLUSION: Argon green laser powers of at least 2.5 and 3.0 W were necessary to rupture Bruch's membrane and the retinal vein, respectively, with a 100% success rate in the porcine eye. Because patients with central retinal vein occlusion have secondary retinal edema and may have lenticular opacity, higher laser powers may be required to achieve a 100% rupture rate of these structures.

Anastomosis, Surgical↗

PubMedDate not supplied

A new skeletal muscle linear-pull energy convertor as a power source for prosthetic circulatory support devices [corrected].

Previous studies show that stimulated skeletal muscle wrapped around the heart or a blood pumping pouch can provide partial circulatory assistance. However, skeletal muscle is accustomed to pulling in direct tension, and power obtained from using the muscle in wraparound configurations is very inefficient. Therefore we have developed a new skeletal muscle-powered, linear-pull energy convertor for powering a wide range of implanted devices, including circulatory support blood pumps such as counterpulsation devices or complete prosthetic ventricles. This energy convertor system is powered by a skeletal muscle such as the latissimus dorsi, which is stimulated with a pulse generator. With the muscle left intact and in situ as much as possible, its insertion at the humerus is removed and reattached to a small-cylinder hydraulic energy convertor that is firmly attached to the ribs. Mechanical force in direct tension from the muscle is converted to high-pressure, low displacement; hydraulic energy (at approximately 200 psi). The output of this hydraulic energy convertor is connected by a small-diameter tube to a hydraulic actuator to drive the pusher plate of an implantable ventricular assist device located in the thoracic cavity or abdomen or another suitable blood pump. Preliminary in vitro tests from an engineering model of the Thoratec muscle-powered ventricular assist device show flow outputs of 5.2 L/min at a mean arterial pressure of 99 mm Hg. The muscle-powered ventricular assist device is a specific application designed to provide completely implantable circulatory support as an alternative to heart transplantation. It will enable patients to experience a quality of life free from batteries and the electrical power-conditioning hardware required with electromechanical systems.

Bioelectric Energy Sources↗

PubMedDate not supplied

[Sex differences in EEG power changes in retention of dichotically and monaurally presented verbal stimuli].

EEG power mapping was used to study gender differences in hemispheric functional organization during memorizing dichotically and monaurally presented verbal information. Right-handed students (12 men and 14 women) participated in experiments. The EEG was recorded from 16 electrodes placed at homologous sites of the left and right brain hemispheres. Task-related changes in the thetal power in men differentiated between monaural presentations to different ears, i.e., situations of oppositely directed attention. In women the thetal power reactivity (the difference between the band power logarithms under baseline conditions and in task interval) differentiated between dichotic and monaural presentations of words, i.e., situations with different memory loads. Gender differences were also found in the alpha frequency band. Power changes in the alpha 1 band in all memory tasks and power changes in the alpha 2 were more evident in the right hemisphere in men but in the left hemisphere in women. In contrast, in the posterior temporal lead the alpha 2 power reactivity in men was higher in the right hemisphere, whereas in women the lateral differences were absent. As compared to men, the alpha 2 desynchronization in women was also more pronounced in posterior regions of both hemispheres. There were no gender differences in efficacy of memorizing. It is suggested that different processing strategies rather than different behavioral performance may be responsible for the revealed specific spatiotemporal EEG patterns.

Adult↗

PubMed2002

[Exposure to power-frequency magnetic fields can induce activation of P38 mitogen-activated protein kinase].

OBJECTIVE: To study the effects of 50 Hz power-frequency magnetic fields on signal transduction pathway of P38 mitogen-activated protein kinase (P38 MAPK), and explore the cellular signal transduction mechanism of the biological effects induced by power-frequency magnetic fields. METHODS: Chinese hamster lung (CHL) cell line was exposed to power-frequency magnetic fields with two intensities(0.1 and 0.4 mT) for different exposure durations. The cytoplasmic protein was extracted. The phosphorylated(activated) and non-phosphorylated P38 MAPK and MKK3/MKK6 were measured by Western blotting analysis with their specific corresponding antibodies. RESULTS: Power-frequency magnetic fields at 0.4 mT for 10 min could transitorily induce the activation of P38 MAPK and after 15 min the phosphorylation of P38 MAPK restored to control level, while 0.1 mT power-frequency magnetic fields could not induce the activation of P38 MAPK within 24 h. However, both 0.1 mT and 0.4 mT power-frequency magnetic fields could not phosphorylate(activate) the MKK3/MKK6, which is a general upstream kinase of P38 MAPK. CONCLUSION: Power-frequency magnetic fields could transitorily activate the P38 MAPK, but not MKK3/MKK6. The activation mechanism of P38 MAPK needs to be further identified.

Animals↗

PubMed2004

[Premature ventricular contraction during myocardial contrast echocardiography: relationship with imaging method, acoustic power and dose of contrast agent].

OBJECTIVES: This study investigated the influence of imaging method, acoustic power, and dose of contrast agent on the occurrence of premature ventricular contraction during myocardial contrast echocardiography. METHODS: Myocardial contrast echocardiography was performed with a Toshiba POWER VISION 6000 and YM454 (Definity in USA) contrast agent. Myocardial contrast echocardiography in the short-axis view at the mid-papillary muscle level and electrocardiography in lead II were recorded on videotape in nine awake beagles. The imaging method was continuous, using 1:1 and 1:4 intermittent end-systolic triggered mode. Acoustic power was low, middle and high (as mechanical index, 0.4, 0.8 and 1.0 at continuous mode and 0.6, 1.0 and 1.4 at intermittent mode). YM454 was given intravenously at doses of 1, 10, 30, 50 and 100 microliters/kg/min. Premature ventricular contractions were counted on the videotape for each experimental condition. The examination was repeated on a separate day to ascertain the reproducibility. RESULTS: At low and middle acoustic power, no premature ventricular contraction was induced with any combinations of YM454 doses and trigger intervals. The highest incidence of premature ventricular contraction was 5.1% of all ultrasound pulses at the combination of high acoustic power, 1:4 intermittent and 30 microliters/kg/min of YM454. All premature ventricular contractions induced by trigger mode were observed concomitantly to the end-systolic phase. Reproducibility was low at 0.9%. CONCLUSIONS: Although high acoustic power, intermittent myocardial contrast echocardiography with high dose of contrast agent induced premature ventricular contractions, the incidence of premature ventricular contractions was low. Low acoustic power or low dose of contrast agent induced no premature ventricular contractions.

Animals↗

PubMed2004

[Characteristics of the EEG power and coherent structure of term and premature children during the first postnatal year].

Objective of the study involved characteristics of the spectre of the EEG power and coherent structure in children of different degree of maturity in the first month of their postnatal development. 32 children were divided into three groups: 1) 38-41 weeks (11 children); 2) 34-36 weeks (12 children); 3) 30-33 weeks (9 children). At the moment of the study the children's chronological age was as follows: in the 1st and 2nd groups--19 +/- 1, in the 3rd group--30 +/- 4 days. In the 1st group (mature children), a considerable power of delta- and theta-range frequencies was registered as compared with the 2nd and 3rd groups. In the 1st group children, a central gradient of power of the delta and theta frequencies was noted as well as a central-occipital one for alpha-frequencies. In the 2nd group (34-36 weeks), a lesser power of the delta-, theta- and alpha-frequencies was noted as well as a smoothed central gradient of these frequencies as compared with the 1st group. In the 3rd group, the power of delta-frequencies in frontal leads and power of alpha-frequencies in most EEG leads did not differ from those in the 1st group, and an obvious frontal gradient of delta-frequency power was noted as well as the frontal-central one for the theta- and alpha-frequencies. In all the groups, three foci of coherent interaction among the brain areas were registered: anterior, central and posterior. The coherence of biopotentials was registered on the frequencies of delta-, theta- and alpha-ranges. The maximum level of coherence was registered in the delta-range. In immature children, as compared with mature ones, a higher level of coherence was registered in the theta- and alpha-frequencies.

Brain↗

PubMed2004

Manual versus powered toothbrushes: a summary of the Cochrane Oral Health Group's Systematic Review. Part II.

PURPOSE: A systematic review examining the clinical effectiveness of power versus manual toothbrushes was conducted by the Cochrane Collaborations Oral Health Group. Their review examined clinical trials conducted through 2001 and used international standards to identify, access, evaluate, analyze, and report the data. Part I of this series discussed distinguishing characteristics of evidence-based publications, such as systematic reviews, whereas this report provides a summary of the Cochrane Review, its importance to the profession, and discusses the strengths and limitations of systematic reviews. METHODS: Search strategies to identify published clinical trials on power toothbrushes were developed, and manufacturers were contacted for additional published and unpublished information. Trials were selected based on pre-established criteria; including whether they compared power versus manual toothbrushes used a randomized research design tested products in the general population without disabilities, provided data on plaque and gingivitis, and were at least 28 days in length. Six reviewers independently extracted information in duplicate. Indices for plaque and gingivitis levels were expressed as standardized mean differences for data distillation. Data distillation was accomplished using a meta-analysis, with a mean difference between power and manual toothbrushes as the measure of effectiveness. RESULTS: Searches identified 354 trials, of which 29 met inclusion criteria. These trials involved 2.547 participants who provided data for meta-analysis. Results indicated that for both plaque and gingivitis, all types of power toothbrushes worked as well as manual toothbrushes, however only the rotating oscillating toothbrush consistently provided a statistically significant though modest benefit over manual toothbrushes in reducing plaque (7%) and gingivitis (17%). None of the battery powered toothbrush studies met the inclusion criteria. CONCLUSION: The Cochrane systematic review used international standards to examine more than 30 years of published studies. A concern is that only one type of electric toothbrush, the rotating oscillating toothbrush consistently demonstrated a statistically significant benefit over manual toothbrushes, and the majority of studies did not meet the standards for inclusion in moving forward it will be important to conduct methodologically sound studies demonstrating the ability of power toothbrushes to reduce the incidence and prevalence of caries and periodontal disease.

Decision Making↗

PubMed2006

[Comparison of the powered-assisted adenoidectomy with adenoid curette adenoidectomy].

OBJECTIVE: To compare the outcomes of powered-assisted adenoidectomy with adenoid curette adenoidectomy. METHOD: Thirty-four cases with adenoidal hypertrophy were retrospectively analyzed in Shanghai Sixth Peoples Hospital between June 2003 to June 2004. All the patients were followed up six to twelve months. Of 34 cases, 18 children underwent powered-assisted adenoidectomy, and the rest underwent conventional transoral adenoidectomy using a curette. The surgical results were assessed by acoustic rhinometry. RESULT: The averaged time for endoscopic powered-assisted adenoidectomy was 5 minutes and 15 seconds and the time for conventional adenoidectomy was 8 minutes and 22 seconds. There was a significant difference (P < 0.01) between them. The blood loss during powered-assisted and conventional adenoidectomy was 50 (10-125) ml and 75 (5-175) ml respectively, but there was no difference (P > 0.05). One case after powered-assisted adenoidectomy happened bleeding, and one case after conventional adenoidectomy happened dehydration. There were increases in the cross-sectional area at the adenoid, (0.75 +/- 0.58) cm2 preoperatively and (1.94 +/- 0.63) cm2 three months postoperatively, (1.99 +/- 0.44) cm2 one year after operation in powered-assisted group, and (0.80 +/- 0.53) cm2 preoperatively and (1.83 +/- 0.81) cm2 three months postoperatively, (1.89 +/- 0.37) cm2 one year after operation in conventional group. Comparing the preoperative and postoperative cross-sectional area in both groups by acoustic rhinometry, a significant difference (P < 0.01) was found. CONCLUSION: Powered-assisted adenoidectomy has the advantages of shorter surgical time, and less blood loss. Acoustic rhinometry is a kind of objective parameter for assessing the outcome of adenoidectomy.

Adenoidectomy↗

PubMed2006

Assessment of power output in jump tests for applicants to a sports sciences degree.

AIM: Our study aimed: 1) to describe the jump performance in a population of male applicants to a Faculty of Sports Sciences, 2) to apply different power equations from the literature to assess their accuracy, and 3) to develop a new regression equation from this population. METHODS: The push off phases of the counter-movement jumps (CMJ) on a force platform of 161 applicants (age: 19+/-2.9 years; weight: 70.4+/-8.3 kg) to a Spanish Faculty of Sports Sciences were recorded and subsequently analyzed. Their hands had to be placed on the hips and the knee angle during the counter movement was not controlled. Each subject had 2 trials to reach a minimum of 29 cm of jump height, and when 2 jumps were performed the best trial was analyzed. Multiple regression analysis was performed to develop a new regression equation. RESULTS: Mean jump height was 34.6+/-4.3 cm, peak vertical force 1 663.9+/-291.1 N and peak power 3524.4+/-562 W. All the equations underestimated power, from 74% (Lewis) to 8% (Sayers). However, there were high and significant correlations between peak power measured on the force platform, and those assessed by the equations. CONCLUSIONS: The results of the present study support the development of power equations for specific populations, to achieve more accurate assessments. The power equation from this study [Power = (62.5 x jump height (cm)) + (50.3 x body mass (kg)) 2184.7] can be used accurately in populations of male physical education students.

Adolescent↗

PubMedDate not supplied

Statistical power in nursing research.

A power analysis was performed on 62 articles that were published in Nursing Research and Research in Nursing and Health during 1989. The analysis revealed that when effects were small, the mean power of the statistical tests being performed to test research hypotheses was .26, indicating a very high risk of committing a Type II error. When effects were moderate, the mean power increased to .71, which is still below the conventionally acceptable power of .80. Only when a study involved large effects was the power adequate (mean of .95). Of the 583 power estimates calculated, 53% were for small effects. These analyses indicate that a substantial number of published nursing studies, and presumably even more of unpublished studies, have insufficient power to detect real effects, primarily because the samples used are too small.

Nursing↗

PubMed1990

Frequency analyses of EMG power spectra of anterior temporal and masseter muscles in children and adults.

To study the functional change of masticatory muscles during growth and development, frequency analyses of surface electromyogram (EMG) power spectra were carried out. The subjects were six children (five males and one female), aged 4.5 +/- 0.2 years, having full deciduous dentition (Hellman's dental age IIA) and six adults (four males and two females), aged 27.7 +/- 3.8 years, having full permanent dentition. EMG signals were recorded bilaterally by using bipolar silver-surface electrodes from the anterior temporal and masseter muscles while the subjects were chewing gum and while performing maximum clenching in the intercuspal position. A fast Fourier transform algorithm was used to obtain the power-spectral density function and the power spectra of the EMG signals. Since the total power value from 62.5 to 1000 Hz was 100 percent, the frequencies at 25, 50, 75, and 90 percent of the cumulative power were calculated. The results showed that the frequencies at every percent of the cumulative power were age-dependent and that the EMG power spectra patterns in adult muscles were shifted to significantly lower frequencies than those in child muscles. The shift was probably caused by differences in the proportion of fiber type and fiber size between muscles of children and adults.

Adult↗

PubMed1986

Power spectral analysis of the surface electromyogram during shivering.

The purpose of this study was to describe the frequency content of the electromyogram (EMG) recorded during shivering and determine if the EMG power spectrum changed as a function of the shivering duration. Six semi-nude males were exposed to cold air (5 degrees C, 20% rh) for 80 min while quietly sitting. Rectal (Tre) and mean skin (Tsk) temperatures were recorded. Shivering of the masseter muscle was determined using bipolar surface electrodes. The EMG was amplified, recorded, and subsequently digitized at 2048 Hz. The power spectrum was calculated from eight serial 0.25s EMG samples by Fourier analysis from a frequency of 4 through 480 Hz. The eight power spectra were averaged and centroid frequency (fc) calculated. During the first 10 min of exposure, Tsk rapidly dropped from 32.6 +/- 1.6 to 26.2 +/- 1.3 degrees C, then slowly declined reaching 22.5 +/- 0.7 degrees C after 80 min. Tre rose from 37.1 +/- 0.1 to 37.4 +/- 0.1 degrees C, declining after 40 min to 37.2 +/- 0.1 degrees C. Shivering was observed within 5 min after entering the cold chamber. EMG activity after 10 min exhibited an fc of 177.2 +/- 6.2 Hz. When power was integrated over 60 Hz bandwidths, the predominant frequency band of the EMG power spectrum was 60-120 Hz. Although shivering intensity increased with time, the EMG power spectrum exhibited no significant changes. These results suggest that the EMG power spectrum during shivering did not exhibit changes characteristic of muscle fatigue or muscle cooling during the 80-min cold air exposure.

Adult↗

PubMed1982

The selection of intraocular lens power by calculation and by reference to the refraction--a clinical study.

Two hundred eyes each received a Rayner Binkhorst pupil-supported intraocular lens (IOL) after cataract extraction. One hundred received a standard power +19 D IOL and one hundred received an IOL of power calculated for emmetropia by the formula of R. D. Binkhorst using biometric data. Calculation reduced the incidence of postoperative refractive error greater than the +/- 2 D range from 20 per cent to 1 per cent virtually eliminating significant postoperative refractive error. Consideration of the preoperative refractions and the calculated IOL powers showed that there is no constant or reliable relationship. Twenty nine 'emmetropic' eyes were shown not to be 'normal' eyes but eyes with a wide range of axial lengths whose different optical components summated to give emmetropia. In the selection of IOL power, reference must be made to biometric data to allow for these optical components and for this reason IOL power cannot be determined from the preoperative refraction of the eye. The case for control of postoperative refraction by calculation of IOL power is a strong one and there appears little justification for the use of standard power IOLs with unpredictable refraction results.

Humans↗

PubMed1982

[A new correction method for radionuclide formation in neutron activation analysis using a reactor power meter coupled with a microcomputer].

Neutron flux and irradiation time should be accurately known in neutron activation analysis using very short lived nuclides in which conventional monitoring methods i.e., a comparator method, flux monitor method and so on cannot be used satisfactorily. Especially, fluctuation of neutron flux has not been corrected. We noted a change of reactor power at a pneumatic operation, and found out a new correction method for its correction in activation analysis. In our small nuclear reactor, TRIGA-II, the reactor power increased rapidly a few % when a pneumatic-operated capsule arrived at a core of the reactor, and decreased when the capsule left from the core. If the duration between these two changes of the reactor power is equal to the irradiation time, and that the reactor power is proportional to the neutron flux, we can regard an activity formation as a time integration of the reactor power. Then, the correction system was made of a reactor power meter, a V-F converter (voltage to frequency converter), a clock time, a counter, a microcomputer, electric circuits and so on. The signal of the reactor power during the irradiation was counted through the V-F converter, and was accumulated in a memory of the microcomputer. The neutron fluence was calculated in this microcomputer. This method was examined by means of activation of copper and selenium standard samples by 9-11 sec irradiations. The observed activity involved +/- 10% error. However, the error in the corrected activity was decreased to a few % using this correction method. As a result, we found that this method can be used to obtain accurate value for radionuclide formation.

Activation Analysis↗

PubMed1995

Power spectral analysis of systemic arterial pressure signals during open heart surgery.

BACKGROUND: The close relationship between the balance of sympathetic and parasympathetic tones and the results of power spectral analysis (PSA) of systemic arterial pressure (SAP) has been suggested recently. The purpose of this study was to further describe the changes of balance between the two autonomic nervous components during open heart surgery for coronary arterial disease (CAD) or valvular heart disease (VHD) with the PSA technique of SAP. METHODS: By relaying the SAP signals to a personal computer utilizing a power spectral analysis algorithm, radial arterial pressure signals of 27 patients (11 with CAD for coronary artrial bypass graft, as CAD groups; 16 with VHD, as VHD group, including 8 for aortic valve replacement and 8 for mitral valve replacement) during open heart surgery were monitored in a continuous, on-line and real-time manner. On-line power spectral analysis was performed according to the five different stages of the operation. RESULTS: Power density tended to increase in the high frequency (HF) band during the ventilator-supported stages of the open heart procedures, i.e., the pre-cardiopulmonary bypass (CPB) and the off-CPB periods. The power density in other frequency bands during the whole course of general anesthesia otherwise decreased significantly, with the lowest values occurring during CPB. The power density in very low frequency (VLF) band was much higher than in other bands during CPB, and became the major component of total power density in this period. CONCLUSIONS: The balance between sympathetic and parasympathetic components of autonomic nervous system changes rapidly during open heart surgery and needs careful monitoring. By utilizing PSA of SAP, mathematical error might be an obstacle of using LF:HF ratio as an index of autonomic balance during the CPB period when the HF density approaches zero.

Aged↗