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PubMedDate not supplied

Combined peritoneal dialysis and hemodialysis: our experience compared to others.

OBJECTIVE: To determine the clinical experience of using combined-modality [simultaneous hemodialysis (HD) and peritoneal dialysis (PD)] treatment in patients with end-stage renal disease. DESIGN: We reviewed data on 4 patients from our center that were treated with "combined-mode therapy." We then conducted a retrospective survey by sending questionnaires to nephrologists in the US and Canada by mail and by posting the survey on the Internet. Data queried included number of patients on combined modality, solute clearances, albumin levels pre and post combined therapy, reasons for using combined therapy, duration and success of combined therapy, and reimbursement issues. SETTING AND PARTICIPANTS: Ours is a tertiary-care center. Patients that were not doing well on PD alone were put on combined modality of treatment between 1992 and 1998. MAIN OUTCOME MEASURES: Clinical improvement in the indication for which the participant was started on combined modality. RESULTS: In response to the survey, data on 27 patients were collected. These data were combined with data on 4 patients from our unit that had previously been treated with combined HD and PD. Most patients were reported to have more than one clinical reason for changing from PD to combined therapy. The main clinical reason for offering combined treatments was inadequate solute clearance (34%), followed by ultrafiltration problems (16%) and neuropathy (11%). Mean duration of time followed on combined treatment was 8.5 +/- 0.12 months. Most patients tolerated combined treatment well and were reported to show improvement in the clinical reasons for which they needed the combined modality. Dual access and reimbursement issues were not a problem. There was no single method used for calculating total (HD, PD, and residual renal) solute clearance. No universal total solute clearance goal was reported. CONCLUSION: Hemodialysis and PD are not mutually exclusive. They can be used in combination to achieve targeted solute clearances, to improve certain clinical conditions, and to control volume and blood pressure in a subset of patients. Further evaluation is needed to better establish the long-term outcomes of using combined modality. Total solute clearance goals and methods for determining total solute clearance need to be standardized.

Drug Therapy, Combination↗
PubMed1996

Neural connectivity only accounts for a small part of neural correlation in auditory cortex.

In order to allow the relation of functional connectivity patterns (inferred from cross-correlograms) to structural connectivity (the anatomical substrate), we analyzed cross-correlogram peaks for spontaneous and stimulated activity in the auditory cortex. It was assumed that the broad correlograms, usually encountered, represent neural connectivity as well as secondary effects such as intrinsic firing patterns, global synchrony related to the ongoing electroencephalographic activity, and stimulus-related effects. Data were collected from 604 neuron pairs recorded under spontaneous conditions in primary auditory cortex of seven juvenile (30-70 days) and nine adult cats. Three hundred and six pairs (51%) had a peak cross-correlation coefficient significantly different from zero. For 113 neuron pairs out of this subgroup, correlations were calculated also for spike trains recorded during click stimulation. After a combined burst-correction and deconvolution procedure was carried out, the correlation peak strengths were not significantly changed for spontaneous activity, but peak width was narrower for single-electrode pairs than for dual-electrode pairs, suggesting a better synchronization for neighboring neurons. Under click stimulation conditions, overall peak synchronization strength was independent of interelectrode distance, whereas, after correction for secondary and stimulus effects, peak synchronization was significantly lower for dual-electrode pairs. However, the primary peak width for single-electrode pairs under stimulus conditions was no longer different from that of dual-electrode pairs. This implies that both under spontaneous and stimulus conditions secondary effects largely obscure any underlying correlation produced by anatomical connectivity. The secondary effects may be the result of intrinsic as well as network properties in auditory cortex and may functionally be more important than the weak primary effects resulting from anatomical connections. Cross-interval analysis suggests that the correlations in auditory cortex are dynamic and may show random switching between states of stronger and weaker synchronization.

Acoustic Stimulation↗
PubMed1995

Quality control of DXA instruments in multicenter trials.

Dual-energy X-ray absorptiometry (DXA) has become the measurement of choice for multicenter trials with bone density endpoints. When performing DXA measurements with several different systems, it is important to implement a quality assurance program to guarantee that any observed density changes are real and not due to machine and/or operator variability. In this study, we present a series of procedures based on phantom measurements designed to monitor DXA instrument stability. Techniques for longitudinal evaluation of machine performance and cross-calibration of instruments are described. These procedures are then demonstrated using quality assurance data collected from a number of different DXA scanners. Together these methods provide a defined approach to instrument quality control. Though based primarily on the use of spinal phantoms, these procedures can be generalized for use in any multicenter DXA study.

Absorptiometry, Photon↗
PubMed1983

Data acquisition in neurophysiology. A flexible microcomputer system for recording neurophysiological data.

The advent of the microprocessor, and its incorporation in relatively low-cost microcomputer systems, offers a new range of possibilities for the recording of evoked and event-related potentials. A flexible system for recording evoked potentials, entitled DAN, has been developed using an Apple microcomputer. The main objective in developing DAN was to make it sufficiently flexible so that it could be used in both a research and a clinical environment for a wide range of responses, from the auditory brainstem to much slower cortical responses. A specific response can be selected from a standard range of evoked responses, or if a non-standard response is required, it is a simple matter to specify the response stimulus parameters, time duration and data sampling rate. This degree of versatility is achieved by designing a programmable audiometer, a special-purpose hardware interface for the Apple and software to generate the stimulus and control the data-acquisition interface. The main hardware components of the DAN system are listed (a) Apple microcomputer operating under U.C.S.D. PASCAL operating system; (b) dual 5 1/4 inch floppy disk drives and controller; (c) Video monitor; (d) DAN data-acquisition interface; (3) programmable audiometer; (f) Epson MX-80 printer/plotter. Disk drive 1 of the dual drive set is used to store the PASCAL operating system and the DAN programs. Drive 2 is used to store the data. The data-acquisition interface and audiometer interface plug into slots in the Apple. The software includes routines to generate the stimulus and store it in the audiometer prior to the data-acquisition phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Computers↗
PubMed1984

Dual-mode computer processing for high resolution DNA thermal denaturation experiments.

Two modes of data processing are appropriate in conducting high resolution thermal denaturation experiments (thermal increments of 0.05 degrees or closer). In the first mode, a general purpose microcomputer provides on-line services important to the control and monitoring of the initial experiment, including control of the spectrophotometer and heater, the recording of data, and the display of current hyperchromicities and approximate first derivatives. A subsequent microcomputer program then reads the recorded data files and carries out accurate calculations of derivative denaturation profiles and the estimate of the statistical error of the first derivative at each point. The data collection program handles three samples at a time and was designed to provide optimal results in thermal denaturation experiments with a single-beam spectrophotometer.

Computers↗
PubMed1991

RBRVS: execs defuse touchy med staff issues.

The Medicare program's anticipated implementation of Harvard's resource-based relative value scale to physician reimbursement is creating dual headaches for hospitals, executives say. Although physician payment reform won't come on-line until 1992, some physicians are already moving services off-campus to offset anticipated income losses, experts say. The result: Hospitals face lower revenues and increasing tension as they compete for services with their medical staffs.

Attitude of Health Personnel↗
PubMed1982

A dual-channel signal averager for spontaneous signals.

This signal averager has been developed for spontaneous transients of tension and of aequorin bioluminescence in skinned cardiac cells. The signal with the largest signal-to-noise ratio (generally the tension transient) is entered in Channel 1 and triggers the system. Then the averager will unmask the signal entered in Channel 2 if it was buried in the noise during the direct recording. This signal averager uses an inexpensive microcomputer and a program written in Assembly Language. To facilitate its use, the averager is remotely controlled by a potentiometer for the adjustment of the threshold voltage above which the signal in Channel 1 will be collected and by three push buttons for starting the data collection, for averaging and displaying the results, and for resetting the system. The display is purely analog on the recorder, including averaged signals and interval for the signals in both channels together with a graphical representation of the standard deviations and of the number of observations. This signal averager could be used for any preparations developing spontaneous signals with variable intervals, provided that at least one of the synchronous signals has a large enough signal-to-noise ratio to trigger the system.

Action Potentials↗
PubMed2005

Cyclosporine-based immunosuppressive strategies for kidney recipients: interim analysis of German data from the Multinational Observational Study (MOST).

INTRODUCTION: We collected data from kidney recipients with a functioning graft at German kidney transplant centers in order to analyze the efficacy of various cyclosporine (CsA)-based immunosuppressive strategies, the effects of different perioperative and maintenance regimens, and the impact of donor source on clinical outcome. METHODS: As part of the ongoing prospective Multinational Observational Study in Transplantation (MOST), data for both prospective and retrospective analysis were collected from kidney recipients over 18 years bearing a functioning graft that was transplanted at 21 German kidney transplant centers between 1987 and 2002. RESULTS: Data from 1223 renal graft recipients, including their CsA-based immunosuppressive regimens, were stratified as: 402 de novo patients (median 6.8 months posttransplant) and 821 patients on maintenance therapy (median 71 months posttransplant). Triple regimens with CsA + mycophenolate mofetil (MMF) + steroids (Ste) currently comprise the major perioperative immunosuppressive strategies in Germany (de novo 65%). IL-2 receptor antagonist (IL-2Ra) use is increasing (de novo 18%, maintenance 4%), while mono and dual regimen use de novo is declining (de novo 4%, maintenance 20%). Among 689 patients transplanted between 1987 and 2002 with outcome data, the mean incidence of acute rejection during the first posttransplant year was 21.6%. Rejection rates on initial therapy with CsA + MMF + Ste +/- antibodies (n = 517) averaged 17.8%. CONCLUSIONS: Between 1987 and 2002, CsA-based immunosuppression combined with MMF and Ste became the most commonly used strategy for both initial and maintenance therapy after kidney transplantation in Germany, yielding the low acute rejection rates particularly when combined with IL-2Ra.

Adult↗
PubMed1999

Posterior 180 degrees 99mTc-dimercaptosuccinic acid renal SPECT.

UNLABELLED: As a result of a high percentage of hypoactive upper poles of kidneys in traditional 99mTc-dimercaptosuccinic acid (DMSA) SPECT, a prospective study was conducted using 180 degrees acquisition technique compared with 360 degrees to minimize tissue attenuation. METHODS: Anterior 180 degrees, posterior 180 degrees and 360 degrees renal SPECT images were obtained simultaneously using a dual-head camera. Forty-one subjects without renal disease and 16 subjects with 21 cortical defects were included in this study. The total counts of the raw data in the anterior 180 degrees, posterior 180 degrees and full 360 degrees were calculated. Small regions of interest were drawn over the cortex of the kidney on coronal and reoriented sagittal slices. Quantitative evaluation of regional activity was performed on the same frames in all three acquisition methods. RESULTS: Comparison of the total renal counts between the anterior and posterior 180 degrees data showed reduced counts in the anterior 180 degrees data collection (P < 0.01). Visual evaluation of the reconstructed images from anterior 180 degrees, posterior 180 degrees and full 360 degrees data collection showed the best image uniformity in the posterior 180 degrees image. The upper/lower pole ratio in the posterior 180 degrees renal SPECT images increased significantly in comparison to full 360 degrees renal SPECT images (P < 0.01) and anterior 180 degrees SPECT images (P < 0.01). The renal defects were more clearly visualized in the posterior 180 degrees renal SPECT images than the full 360 degrees renal SPECT images. The defect/normal cortex ratios in the posterior 180 degrees renal SPECT images were much lower than those from the full 360 degrees SPECT images (P < 0.01) and those from the anterior 180 degrees SPECT images (P < 0.01). CONCLUSION: The posterior 180 degrees acquisition technique can avoid the problem of hypoactive upper pole and can be less time consuming in 99mTc-DMSA SPECT images. It also provides superior lesion contrast in the clinical evaluation of patients with renal scarring.

Child↗
PubMed1996

Dual X-ray absorptiometry quality control: comparison of visual examination and process-control charts.

Dual X-ray absorptiometry (DXA) is widely used to monitor treatment efficacy in reducing the rate of bone mineral loss. In order to assure the validity of these measurements, instrument quality control of the DXA scanners becomes very important. This paper compares five quality control procedures (visual inspection, Shewhart chart with sensitizing rules, Shewhart chart with sensitizing rules and a filter for clinically insignificant mean changes, moving average chart and standard deviation, and cumulative sum chart [CUSUM]) in their ability to identify scanner malfunction by means of (1) an analysis of five longitudinal phantom data sets that had been collected during a clinical trial and (2) an analysis of simulated data sets. The visual inspection method is relatively subjective and depends on the operator's experience and attention. The regular Shewhart chart with sensitizing rules has a high false alarm rate. The Shewhart chart with sensitizing rules and an additional filter for clinically insignificant mean changes has the lowest false alarm rate but a relatively low sensitivity. The CUSUM method has good sensitivity and a low false alarm rate. In addition, this method provides an estimate of the date a change in the DXA scanner performance might have occurred. The method combining a moving average chart and a moving standard deviation chart came closest to the performance of the CUSUM method. Comparing the advantages and disadvantages of all methods, we propose the use of the CUSUM method as a quality control procedure for monitoring DXA scanner performance. For clinical trials use of the more intuitive Shewhart charts may be acceptable at the individual sites provided their scanner performance is followed up by CUSUM analysis at a central quality assurance center.

Absorptiometry, Photon↗
PubMed2004

Energy cost and intracyclic variation of the velocity of the centre of mass in butterfly stroke.

The purpose of this study was to examine the relationship between the intra-cycle variation of the horizontal velocity of displacement (dV) and the energy cost (EC) in butterfly stroke. Five Portuguese national level swimmers performed one maximal and two sub-maximal 200-m butterfly swims. The oxygen consumption was measured breath-by-breath by portable metabolic cart. A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and to collect breathing air samples. Blood samples from the ear lobe were collected before and after each swim to analyse blood lactate concentration. Total energy expenditure ( E (tot)) and EC were calculated for each swim. The swims were videotaped in the sagittal plane with a set of two cameras providing dual projection from both underwater and above the water surface. The APAS system was used to analyse dV for the centre of mass. The E (tot) increased linearly with the increasing V, presenting a significant correlation coefficient between these parameters ( r =0.827, P <0.001). The increase in EC was significantly associated with the increase in the dV ( r =0.807, P <0.001). All data were presented as the mean value and the standard deviation. It is concluded that high intra-cycle variation of the velocity of the centre of mass was related to less efficient swimming and vice versa for the butterfly stroke.

Adolescent↗
PubMed2000

Evaluation of the novel Tanita body-fat analyser to measure body composition by comparison with a four-compartment model.

The Tanita body-fat analyser is a novel device to estimate body fat, based on the principles of bioelectrical impedance. It differs from other impedance systems which use surface electrodes in that the subjects stand bare-footed on a metal sole-plate which incorporates the electrodes, hence impedance is measured through the legs and lower trunk. In 104 men and 101 women (16-78 years and BMI 16-41 kg/m2) the mean bias in body-fat mass measured using the Tanita body-fat analyser was 0.8 (2SD 7.9) kg relative to a four-compartment model. This is comparable to the other prediction techniques tested (conventional tetrapolar impedance -1.3 (2SD 6.9) kg, skinfold thicknesses 0.3 (2SD 7.4) kg, and BMI-based formulas -0.2 (2SD 9.0) kg and -0.6 (2SD 8.5) kg), but the agreement was poorer than for 'reference' methods to measure body fat (density 0.2 (2SD 3.7) kg, total body water -0.9 (2SD 3.4) kg and dual-energy X-ray absorptiometry 0.1 (2SD 5.0) kg). The present paper also describes the derivation of a new prediction equation for the calculation of body composition from the Tanita body-fat analyser. The equation incorporates sex, age, and a log-transformation of height, weight and the measured impedance to predict body fat measured by a four-compartment model. This approach is recommended in the derivation of other prediction equations in body composition analysis. Using this novel prediction equation the residual standard deviations were 4.8% for men and 3.3% for women. A similar analysis using data collected with a conventional tetrapolar system yielded residual standard deviations of 4.3% for men and 3.1% for women. This demonstrates that the practical simplicity of the novel Tanita method is not associated with a clinically significant decrement in performance relative to a traditional impedance device.

Absorptiometry, Photon↗
PubMed2005

The course of bone mineral density and biochemical markers of bone turnover in early postmenopausal spinal cord-lesioned females.

STUDY DESIGN: A prospective observational study. OBJECTIVE: To evaluate bone mineral density (BMD) and biochemical markers of bone turnover in spinal cord-lesioned females in the early postmenopausal period. SETTING: Clinic for Spinal Cord Injuries, H:S Rigshospitalet, Denmark. MATERIAL: In all, 18 early postmenopausal females with spinal cord lesions (SCL) of more than 2 years duration were recruited. In total, 11 completed the study. METHODS: Using dual energy X-ray absorption, BMD of the lumbar spine, femoral neck, trochanter and proximal tibia was measured every 6 months for 30 months. Biochemical markers of bone turnover in blood and urine were collected at the same time points. RESULTS: A significant increase in markers of bone formation in the blood was found and markers of bone resorption in urine tended to increase. BMD values changed insignificantly but for all regions decreased, except the lumbar spine. CONCLUSION: An accelerated bone turnover occurs in early postmenopausal SCL females. At the same time, we showed an insignificant decrease in BMD data from the lower extremity.

Absorptiometry, Photon↗
PubMedDate not supplied

Multi-detector row CT evaluation of living renal donors prior to laparoscopic nephrectomy.

Since its introduction in 1995, laparoscopic nephrectomy has become the preferred technique at many medical centers for the harvesting of kidneys from living donors for transplantation. Because the field of view at laparoscopic surgery is limited, preoperative radiologic evaluation of the donor's anatomy---the renal veins and arteries, collecting system, and parenchyma--is critical. Spiral computed tomographic (CT) angiography is a fast, safe, minimally invasive, and generally accepted method for preoperative evaluation of the renal vessels. Multi-detector row CT scanners offer shorter image acquisition time, narrower collimation, better spatial resolution, and less tube heating than do single-detector row CT scanners. Multi-row scanners also provide more complete anatomic coverage, increased contrast enhancement of the arteries, and greater longitudinal spatial resolution--all of which are important both for accurate imaging of the renal vasculature and for three-dimensional postprocessing of image data. Dual-phase multi-detector row CT angiography combined with three-dimensional postprocessing enables minimally invasive and highly accurate depiction of the preoperative donor anatomy. To make the most effective use of this method, radiologists must be familiar with its technical aspects, advantages, and potential pitfalls. They also must be able to identify variations in vasculature and in renal and extrarenal anatomy that are important for laparoscopic donor nephrectomy.

Equipment Design↗
PubMed2003

Determinants of contraceptive method among young women at risk for unintended pregnancy and sexually transmitted infections.

The objective of this study was to examine the relationship between contraceptive method choice, sexual risk and various demographic and social factors. Data were collected on 378, 15- to 24-year-old women, recruited from health clinics and through community outreach in Northern California. Logistic regression analysis was used to estimate the association of predictors with contraceptive method used at last sex. Asian and Latina women were less likely to use any method. Women who were raised with a religion, or thought they were infertile, were also less likely to use any method. Women with multiple partners were generally less likely to use any method, but were more likely to use barrier methods when they did use one. Few women (7%) were dual method users. Women appear to act in a rational fashion within their own social context and may use no methods at all or use methods that are less effective for pregnancy prevention but offer more protection from sexually transmitted infections.

Adolescent↗
PubMed1997

Oral regurgitation after reflux provoking meals: a possible cause of dental erosion?

Certain foods and drinks such as alcohol, heavily spiced or fatty meals are known to provoke gastro-oesophageal reflux (GOR). This may give rise to symptoms of heartburn, epigastric pain and occasionally oral regurgitation of the gastric contents. Oral regurgitation of gastric juice is important in dentistry because of its association with dental erosion. This study measured oesophageal and oral reflux in 12 healthy subjects after a curry meal taken with alcohol 2 h before sleep. Each subject repeated the test with a bland non-reflux provoking control meal. GOR was measured by recording distal and proximal oesophageal pH on a dual channel, portable pH monitor. Oral pH was measured with a pH sensitive radio-telemetry capsule (RTC) held on the palate in a vacuum formed splint. Signals from the RTC were received by an aerial worn around the head. The pH change produced by GOR was estimated as the percentage time that pH (PTpH) was less than 4 in the distal oesophagus. Similarly, the PTpH was estimated < 4 and < 5 in the proximal oesophagus and < 5.5 and < 6 in the mouth over a period of 16 h. All subjects tolerated the monitors overnight with little loss of data and data were collected from all studies. The curry meal provoked GOR in all subjects, but only in six subjects to pathological levels according to international guidelines. The results show that GOR measured as the PTpH < 4 was significantly higher in the distal oesophagus whilst subjects were supine after the curry meal than with the control meal (P = 0.0006) and in the proximal oesophagus in the upright position (P = 0.006). There was a significant difference in the oral PTpH < 5.5 between the two meals for the total study period (P = 0.005). The bland meal provoked pathological levels of reflux in only two subjects. In one of these subjects the bland meal provoked oral regurgitation with a PTpH < 5.5 of 13.5%. In the remaining subjects little oral regurgitation occurred.

Adult↗
PubMed1992

Application of a programmable dual-channel adaptive electrical stimulation system for the control and analysis of gait.

A dual-channel electrical stimulation system with a stimulator and a programmer/stride analyzer was designed for clinical rehabilitation of gait and for subsequent daily use as an orthotic aid. The stimulator, with controls to adjust amplitude only (50 mA), adapts chosen stimulation sequences to the walking rate of a patient. Pulse duration (50-500 microseconds), frequency (5-120 Hz), shape (symmetrical biphasic, monophasic), stimulation sequences (16 stride segments) and their cycle (2-12 sec), and right/left foot-switch choices are selected for each patient and programmed into a separate unit. The programming unit also statistically processes the foot-switch data collected by the stimulator. The device was evaluated with regard to the programmable parameters, effectiveness during gait, and feasibility in clinical use. It was applied to 11 stroke patients and 10 brain injury patients during gait, stimulating 22 combinations of peroneal nerve and hamstring, quadriceps, triceps brachii, and gluteus maximus muscles. Forces on both feet, equinovarus, knee extension and hyperextension, elbow flexion, and hip extension were corrected. Selection of the stimulation sequences, their adaptation, range of pulse duration, and valid statistics were verified. Improved forces and joint angles were recorded together with significant changes in the stride time, length, and velocity by the stimulation.

Adult↗