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PubMed1985

Arteriovenous shunt measured by bolus dye dilution: reproducibility and comparison between two injection sites.

Twenty-eight brachial arteriovenous fistulae (AVF) flows were assessed by the Stewart and Hamilton method by bolus dye injection. These measurements were divided in two groups: a first group with dye injection into the AVF artery and a second group with dye injection into the efferent vessel of the AVF in close proximity. The increase and the decrease of dye concentration were regular and the circulation occurred very late in both groups. Reproducibility was assessed by the usual index: the mean of the differences between two successive measurements of each series related to the first of these two and expressed as a percentage, m(Qn - Qn - 1)/Qn%. In the two groups, the reproducibility index was at 10.1%, similar to the index applied to Grimby's results, measuring successive cardiac output by dye bolus injection at 9.8%. Theoretical criteria of validity of the Stewart and Hamilton method were checked for all measurements. Even when the duration of the measurement was very short, arteriovenous flow fulfilled the criteria of validity in the same way as cardiac output. Two AVF flows were measured successively at both injection sites with no difference between the obtained values. The same reproducibility of the efferent vessel injection site group suggests that an arterial puncture is not necessary for a correct assessment of AFV flow.

Adult↗

PubMed1992

Dual-energy x-ray absorptiometry of the forearm: reproducibility and correlation with single-photon absorptiometry.

Although single-photon absorptiometry (SPA) has been the predominant tool used to assess bone mineral density (BMD) in the forearm, the development of dual-energy x-ray absorptiometry (DEXA) provides the benefits of greater source stability, reduced scanning time, and improved image resolution compared to SPA. In the present study we used the DEXA bone densitometer (Hologic, Inc., Waltham, MA) to (1) measure BMD in the one-third radius and ultradistal radius; (2) examine the reproducibility of these BMD measurements; and (3) compare the BMD at the one-third radius with SPA (SP2, Lunar Corp., Madison, WI). In 65 normal women (ages 22-74 years) we examined changes in the forearm DEXA BMD with age, revealing significant quadratic regression equations. The reproducibility of DEXA BMD (mean +/- SEM) in 7 normal subjects aged 22-50 years is 0.85 +/- 0.16% for the predominantly cortical one-third radius site and 0.97 +/- 0.15% for the more trabecular ultradistal site. The regression relationship between DEXA and SPA of the one-third radius in 26 subjects (ages 22-68 years) is DEXA BMD = 0.105 + 0.826 (SPA BMD); R = 0.97, R2 = 0.94, p less than 0.0001. Bone densitometry of the forearm using DEXA may be performed relatively rapidly, providing reproducibility and image resolution that are generally superior to those observed with SPA.

Absorptiometry, Photon↗

PubMed2004

Reproducibility of statistical motor unit number estimates in amyotrophic lateral sclerosis: comparisons between size- and number-weighted modifications.

Motor unit number estimations (MUNEs) can directly assess motor unit populations in muscle and quantify the degree of physiological or pathological motor unit degeneration. A high degree of reproducibility and reliability is required of any effective quantitative tool. MUNE is being increasingly applied clinically, and statistical MUNE has several advantages over alternative techniques. Nevertheless, the optimal method of applying statistical MUNE with respect to its reproducibility has not been established. We performed statistical MUNE by selecting the most compensated compound muscle action potential (CMAP) area as a test area and modified the results obtained by using the weighted mean surface-recorded motor unit potential (SMUP). MUNE measurements made in patients with amyotrophic lateral sclerosis (ALS) showed better reproducibility after incorporating the size-weighted modification. Therefore, we suggest that the size-weighted MUNE in combination with the selection of testing "neurogenically compensated" CMAP areas is a more reliable method of statistical MUNE analysis in ALS patients.

Action Potentials↗

PubMed2004

Reproducibility of muscle-fiber conduction velocity estimates using multichannel surface EMG techniques.

The aim of this study was to assess the reproducibility of muscle-fiber conduction velocity (MFCV) estimates obtained from multichannel surface electromyographic (EMG) recordings. Surface EMG signals were collected with a matrix of 61 electrodes during isometric, submaximal (50% of the maximal voluntary contraction torque) contractions of the biceps brachii muscle. Conduction velocity was estimated using multichannel maximum likelihood techniques. Reproducibility of MFCV estimates was assessed varying the number of signals (two to seven) used for the estimate and the distance between detection points (5-30 mm). Intraclass correlation coefficient (ICC) of both initial MFCV values and their rates of change with fatigue increased when increasing number of signals and distance between detection points. ICC of initial MFCV was negative using two signals for MFCV estimate, and it increased to approximately 75% with six to seven signals. Thus, reproducibility of MFCV estimates may be improved significantly using advanced multichannel estimation methods with respect to classic two-channel techniques.

Analysis of Variance↗

PubMed2001

Accuracy of reproducing hand position when using active compared with passive movement.

BACKGROUND AND PURPOSE: Evaluating proprioception is relevant to physical rehabilitation because of its significance in motor control. One method of proprioceptive testing involves having subjects either imitate or point at a joint position or movement which was presented via a passive movement. However, as the muscle spindles are subject to central fusimotor control, the proprioceptive system may be better-tuned to movements created by active muscular contraction than to passive movements. The objective of the present study was to determine whether accuracy of reproducing hand position is dependent on whether proprioceptive input is obtained via an active or a passive movement. METHOD: Thirty-nine healthy volunteers (mean age (+/- SD) 24.6 (+/- 3.6) years) participated in the study. Subjects' right hands, which were obscured from view, were acoustically guided to five targets on a digitizer tablet with either an active or passive upper extremity movement. Subjects were then asked to reproduce the targets' location by either reaching to them with the unseen hand or by use of a laser beam. Distance from target and angular deviations were calculated in both absolute and relative terms. Repeated measures analysis of variance (ANOVA) was performed for each variable followed by predetermined contrasts. RESULTS: Comparison between the active and passive conditions when reconstruction of target location was guided kinaesthetically indicates significant differences in absolute distance, range and angular deviation. The comparison when reconstruction of target location was guided visually indicates significant differences in absolute distance, absolute angle and angular deviation. CONCLUSIONS: The ability to reproduce hand position accurately is enhanced when position is encoded by active upper extremity movement compared with passive movement. The results have implications for the design of strategies for evaluating as well as treating patients with impaired proprioception and limited movement.

Adult↗

PubMed1993

Assessment of the reproducibility of strength and endurance handgrip parameters using a digital analyser.

A group of 40 healthy individuals (27 women and 13 men) participated in a handgrip test and were retested 1-2 months later. A strain-gauge sensor with a digitised signal and computerized printout was used. A 5-s maximal squeeze test was first made three times, followed by one endurance test with 45%-55% power of the maximal value. The best maximal value was most often (42%) achieved in the third (initial test) or second (retest) attempt. The reproducibility of maximal value was very good; the Pearson correlation coefficient between initial test and retest (r = 0.98) was even slightly higher than in studies with older analogue instruments. The difference of maximal values [361 (SD 109) N, initial test and 368 (SD 110) N, retest] was insignificant. A moderate 12% long-term change in maximal value was statistically significant. Reproducibility of the power factor (integrated area of power with time) was also very good in this short test, correlating closely (r = 0.98-0.99) with the maximal value. Other indexes (grip rate, fatigue percentage and relaxation rate) were not stable enough to be practical. Endurance results were somewhat variable (r = 0.73), which implied in the main variable motivation. Only marked changes of over 50% in endurance were statistically significant. Endurance power increased significantly in the retest, which, in spite of an r-value of 0.82, would make its use in a follow-up study difficult. We found the computer-based handgrip test both precise and practical in assessing maximal voluntary strength; endurance was more difficult to reproduce.

Adult↗

PubMed1990

Reproducibility of measurements of coronary narrowings by videodensitometry: unreliability of single view measurements.

Computer-assisted videodensitometry has been shown to be a reliable and reproducible method of measuring absolute and relative coronary narrowings. Using a commercially available analyzer (Vanguard XR70) we confirmed the intra- and interobserver reproducibilities in 34 narrowings in 9 patients. Analyses were performed on normal area and diameter, stenotic area and diameter, percent area stenosis and percent diameter stenosis. For all 6 analyses, excellent intra- and interobserver correlations were found (r = 0.93-0.98), with slopes close to 1 and intercepts close to zero. In a separate study of 16 lesions in 11 patients, each lesion was analyzed in both the RAO and LAO planes. Correlation between the measurements was reasonable with r = 0.76 for the stenotic area and r = 0.75 for the absolute diameter stenosis. However, with suboptimal slopes (0.54 and 0.63 respectively), actual differences between measurements in the two planes were often unacceptably large. These data suggest that videodensitometry is a highly reproducible quantitative angiographic method; however, single view analyses are inadequate for comparative studies.

Absorptiometry, Photon↗

PubMed1981

The oral glucose tolerance test: a comparison of the time points on the basis of limit values, normal dispersion, and reproducibility.

Time points in the glucose tolerance test (GTT) are compared on the basis of limit values, dispersion within a reference population, and reproducibility. We suggest using the distance between a limit value and the median reference value as a measure of the magnitude of abnormality. The distance between 140 mg/100 ml and the median fasting plasma glucose value is chosen as a standard distance and limits for other points in the GTT are calculated to equal this standard distance of abnormality. We suggest that the probability of correctly interpreting an individual result is directly related to the reproducibility of the test and inversely related to the percentage of the total range of values which is dispersed among the normal population. The ratio of reproducibility to percentage normal dispersion is proposed as an index of the probability of correctly interpreting an individual result. According to this index, and probability of correct interpretation varies in order: fasting plasma glucose concentration greater than 3-h greater than 2-h greater than 0.5-h greater than 1-h plasma glucose concentration.

Adolescent↗

PubMed2006

MR arthrography of traumatic anterior shoulder lesions showed modest reproducibility and accuracy when evaluated under clinical circumstances.

INTRODUCTION: We examined the reproducibility and accuracy of high-field MRA in traumatic anterior shoulder instability under conditions resembling clinical practice and assessed the influence of observer experience. MATERIALS AND METHODS: Two radiologists with different experience levels evaluated 61 MRAs. Assessment was independent, blinded and non-sequential. For 40 MRAs, surgical reports were available to assess diagnosis accuracy and influence of observer experience. The assessed lesions were cuff lesions, Hill-Sachs lesions, bony and classic Bankart lesions, greater humeral tuberosity fractures, SLAP lesions and joint capsule lesions. Reproducibility was quantified using kappa coefficients. Accuracy was evaluated with sensitivity and specificity rates, positive and negative predictive values. Differences in the percentage of correctly diagnosed MRAs between the radiologists were tested using McNemar's test for paired proportions. RESULTS: Inter-observer k-values ranged from 0.03 for joint capsule lesions to 0.45 for humeral head lesions. The overall kappa was 0.21 (95% CI; 0.12-0.30). We also observed markedly lower sensitivity and specificity rates than those reported in the literature for most lesions. The more experienced radiologist correctly diagnosed 78.9% of all lesions compared to 65.4% for the less experienced radiologist (P < 0.001; McNemar's test). CONCLUSION: MRA-interpretations of traumatic anterior shoulder instability should be regarded with caution in clinical practice. The experience level of radiologists can affect reproducibility and accuracy.

Adolescent↗

PubMed1998

Interference from short-term memory processing on encoding and reproducing brief durations.

A temporal reproduction task is composed of two temporal estimation phases: encoding of the interval to be reproduced, followed by its reproduction. The effect of short-term memory processing on each of these phases was tested in two experiments. In Exp. 1, a memory set was presented, followed by two successive tones bounding the target interval to be reproduced. During the reproduction of the target interval, a probe was presented, and the subject ended the reproduction by pressing one of two keys, depending on the presence or absence of the probe in the memory set. In Exp. 2, probe recognition was required during the encoding of the interval to be reproduced. Whereas in Exp. 1 reproductions lengthened as a function of memory-set size, in Exp. 2 temporal reproductions decreased with set size. These results support attentional models of time estimation and suggest that short-term memory processing interrupts concurrent accumulation of temporal information.

Adult↗

PubMed1988

Reproducibility of quantitative two-dimensional echocardiography.

In order to assess reproducibility of quantitative planimetry, three physicians trained in two-dimensional echocardiography performed five successive studies on one another over 2 weeks (30 total studies). Then each physician traced each study (90 total tracings) for left ventricular and atrial volumes and ejection fraction by means of a modification of Simpson's rule, and left ventricular mass and average wall thickness by means of a truncated ellipsoid formula. Calculation of intertechnician variability, intertracer variability, and 95% confidence limits showed that measurements of volumes were less reproducible than measurements of ejection fraction, average wall thickness, and mass. Mean intertracer variability of 15% exceeded mean intertechnician variability of 11%; this disparity was magnified in the subject who was technically difficult to image. Ninety-five percent confidence limits were: ejection fraction +/- 7%, average wall thickness +/- 9%, left ventricular mass +/- 12%, left ventricular end-diastolic volume +/- 11%, stroke volume +/- 14%, left ventricular end-systolic volume +/- 15%, and left atrial volume +/- 19%. Reproducible planimetry data can be obtained in normal hearts with the use of a protocol for quantitative imaging and planimetry.

Echocardiography↗

PubMed1981

Comparison of the results and reproducibility of arm and leg exercise tests in men with angina pectoris.

The results and reproducibility of arm and leg exercise tests were compared in 11 men with angina pectoris induced by both forms of testing. Leg testing was performed using a bicycle ergometer; arm testing was performed using the same apparatus modified to permit arm cranking. Subjects performed 2 days of arm and 2 days of leg testing over a 2 week period. Four tests were performed on each test day. The duration of exercise, oxygen uptake, heart rate, systolic and diastolic blood pressures and the rate-pressure product were determined at the onset of angina. Within day and between product were determined at the onset of angina. Within day and between day coefficients of variation were low and similar for arm and leg tests, indicating that both forms of testing are highly reproducible. Performing four tests on a single day did little to reduce variability. Oxygen uptake increased between the first and second arm or leg test on a single day, but there was little change after the second test. Repetition of the arm and leg tests did not affect performance over the study period. It is concluded that the reproducibility of arm exercise testing in men with angina pectoris is comparable with that of leg exercise. Subjects with angina induced by arm exercise who cannot perform leg testing can be evaluated and followed up with arm exercise tests.

Angina Pectoris↗

PubMed1984

Reproducibility and treatment of exercise-induced ventricular tachycardia.

Fourteen patients with exercise-induced ventricular tachycardia (VT) underwent serial treadmill testing, and those with reproducible arrhythmia were treated with a beta-adrenergic blocking agent. In 11 patients (79%), VT of similar rate, morphologic characteristics and duration was reproduced on 2 consecutive treadmill tests performed 1 to 14 days apart. Beta blockade prevented recurrent VT during acute testing in 10 of 11 patients and during chronic therapy in 9. Eight patients had a consistent relation between a critical sinus rate and the onset of VT. In these patients, successful therapy correlated with preventing achievement of the critical sinus rate during maximal exercise. Thus, serial exercise testing is an appropriate means of assessing efficacy of therapy in patients with exercise-induced VT, provided that reproducibility is established on 2 control tests before beginning treatment. Therapy with beta-blocking agents is effective, especially when guided by the presence of a critical sinus rate-VT relation.

Adult↗

PubMed1986

Immediate reproducibility of clinical and nonclinical forms of induced ventricular tachycardia.

This prospective study assessed the immediate reproducibility of clinical and nonclinical forms of ventricular tachycardia (VT) induced by programmed ventricular stimulation. Twenty-three clinical VTs were unimorphic and previously documented and 22 nonclinical VTs (17 polymorphic and 5 unimorphic) were induced in patients with either no documented or suspected history of VT, or documented VT that had a configuration different from that of the induced VT. The stimulation protocol included 1 to 3 ventricular extrastimuli, 2 drive cycle lengths, and 2 right ventricular stimulation sites. Each VT was induced on the first attempt, then the stimulation protocol was repeated twice in the drug-free state. After the first VT induction, 21 of 23 clinical VTs (91%) and 17 of 22 nonclinical VTs (77%) were reinduced on the second attempt. After 2 VT inductions, 21 of 21 clinical VTs (100%) and 15 of 17 nonclinical VTs (88%) were reinduced on the third attempt. The reinduction rates of the clinical and nonclinical VTs were not significantly different. Among the clinical VTs, the reproducibility of the induction technique was 81% after 1 induction and 88% after 2 inductions with the same technique. These results imply that acute drug testing can be reliably performed after 2 inductions but not 1 induction of clinical VT; reproducibility is not helpful in determining whether an induced VT is clinical or nonclinical; and changes in induction technique during drug testing should be interpreted with caution because changes may occur in the absence of drugs.

Adult↗

PubMed1987

Contrast perfusion echocardiography: distribution and reproducibility of myocardial contrast enhancement in coronary artery disease.

A qualitative assessment was undertaken of the echocardiographic distribution of myocardial contrast enhancement after selective intracoronary injections of 2 ml of hand-agitated Urografin solution. The reproducibility and duration of contrast enhancement has also been examined. Forty-five contrast injections were given, 36 into the left and 6 into the right coronary arteries and 3 into bypass grafts of 28 patients undergoing diagnostic arteriography. Myocardial contrast enhancement occurred in 91% of cases. Although contrast enhancement appeared within the expected area of distribution of the artery infused, in no case was enhancement homogeneous. In 4 patients (1 of whom had undergone coronary bypass surgery), contrast enhancement also appeared in areas remote from the expected perfusion territory, in each case due to well established collateral supply seen angiographically. The contrast effect persisted for 71 +/- 26 seconds. Repeat injection in 5 patients (using identical echocardiographic windows) confirmed the reproducibility of the technique. No patient had symptoms related to the injections, although transient left ventricular wall motion abnormalities were observed in 3 cases. High-grade coronary stenoses did not affect distribution of myocardial contrast enhancement, although coronary occlusions produced well defined deficits. Thus, selective intracoronary injections of hand-agitated echocardiographic contrast medium produce regional myocardial enhancement, which probably reflects the perfusion territory of the artery. The technique is safe and reproducible in human subjects. Nevertheless, because regional enhancement after selective coronary injections is not homogeneous, analysis of enhancement deficits is unlikely to provide a clinically useful means of evaluating the functional significance of coronary stenoses.

Angiography↗

PubMed1990

Reproducibility in circadian rhythm of ventricular premature complexes.

To evaluate the existence and reproducibility of a circadian rhythm of ventricular premature complexes (VPCs), 38 patients (mean age 57 +/- 17 years) with greater than or equal to VPCs/hour were studied with 24-hour electrocardiogram Holter monitoring. Nineteen patients had coronary artery disease and 19 had structurally normal hearts. A second Holter electrocardiogram was recorded in all patients from 2 to 47 days (mean 11) after the first. Chronobiologic analysis was made by single and mean cosinor methods. A significant and similar circadian rhythm of VPCs was found in the total sample both on the first (mesor 399, acrophase at 15:08, p less than 0.01) and the second day (mesor 306, acrophase at 14:47, p less than 0.05), with 2 main peaks, the first in the late morning and the second in the afternoon. However, only 18 patients (47%, group A) had a significant individual circadian rhythm of VPCs on both days, whereas 20 (53%, group B) did not have a significant rhythm in greater than or equal to 1 day. A high reproducibility of the circadian rhythm of VPCs was found in group A patients, with a difference of 2.1 +/- 1.8 hours between the acrophases of the 2 days, whereas the difference was 4.4 +/- 3.3 hours in group B patients (p less than 0.01). Among group A patients, 14 (78%) had a VPC rhythm with acrophase occurring during waking hours, whereas the acrophase of 4 (22%) occurred during the night. The reproducibility of the circadian rhythm of VPCs was not influenced by gender, presence of coronary disease, medical therapy, basal VPC number, or day-to-day variability of VPCs, although group A patients were older than group B patients (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1979

Neocortical pyramidal cells: a model with dendritic calcium conductance reproduces repetitive firing and epileptic behavior.

A computer model of a neocortical pyramidal cell has been constructed using ideas similar to those used for hippocampal pyramidal cells. This model has been applied to the study of (a) repetitive firing, and (b) the paroxysmal depolarizing shift (PDS), an important intracellular event during seizures. Although calcium spikes have not been demonstrated directly in neocortical cells, we have postulated (by analogy with hippocampal pyramidal cells) a dendritic calcium conductance and a 'slow potassium' conductance modulated by intracellular calcium ion. With these dendritic ionic conductances, the model is able to reproduce the following experimental features of neocortical pyramidal cells: the afterdepolarization and succeeding afterhyperpolarization after an antidromic spike, and the f-I (firing rate-injected current) curve. Some of the differences between 'fast' and 'slow' pyramidal tract neurons (PTNs) -- narrower spikes and a steeper f-I curve in the fast PTNs -- may be explained by differences in Hodgkin-Huxley potassium kinetics between the two kinds of cell. The same model which faithfully reproduces repetitive firing behavior also reproduces (given appropriate synaptic inputs) the following intracellular events recording during epileptic seizures: (a) a burst of action potentials superimposed on and followed by a PDS, and (b) rapid repetitive firing succeeded by an IPSP. Thus, a single set of parameters can reporduce both normal physiological behavior and 'epileptic' behavior: the particular behavior seen depending on how the cell is stimulated. This overall result is the same as for our model of the CA1 hippocampal cell. It suggests that certain acutely acting epileptogenic agents, e.g. penicillin, may act by increasing synaptic input (perhaps both excitatory and inhibitory) to pyramidal cells, rather than by altering their membrane properties. As in our CA1 hippocampal cell model, bursting seems to be a phenomenon generated by the apical dendrite.

Biophysical Phenomena↗

PubMed1983

Evaluation of the reproducibility of two bitewing techniques by means of a microdensitometric recording method.

A new, simple, metal bitewing holder with a radiation dose-reducing collimator using principles suggested by Eggen is presented and recommended. The reproducibility of the bitewing holder technique was compared with that of the conventional bitewing loop technique. The material consisted of twenty seven sets (fifty four pairs) of radiographs. A microdensitometric method was developed and used to assess the reproducibility of the radiographs, and 108 pairs of microdensitometric tracings were produced to evaluate the two techniques. The results showed that the metal bitewing holder was significantly superior to the bitewing loop for obtaining radiographs with high reproducibility. The suitability of the microdensitometric method is discussed.

Densitometry↗