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At least 793 records · Page 44Linked to original sources
PubMed1991

Ongoing pain as a mental workload indexed by P300 depression: discrimination of real and feigned pain conditions.

Two groups of subjects were formed. One, a real pain group, was subjected to aversive pressure on the fingernail surface during pain-only and pain-tracking conditions. The second group (feigned pain) was instructed to feign pain during corresponding runs in which fingernail pressure was applied at a just noticeable (not painful) level. Both groups also simultaneously performed an auditory oddball (.8/.2) task during their pain-only and pain-tracking conditions, as well as during an initial (baseline-1) and final (baseline-2) baseline condition in which only the oddball task was performed. Oddball-evoked P300 amplitudes were significantly different for the groups during the pain-tracking and baseline-2 conditions, with the amplitudes smaller in the real pain groups in both conditions. The pain-only and pain-tracking conditions in both groups caused significant P300 reductions in comparison with baseline-1 values. P300 latencies did not differ as a function of either groups or conditions. 100% of the real pain subjects and 67% of the feigned pain subjects could be correctly classified using P300 amplitude-derived indices.

Adult↗
PubMed1992

Masticatory muscle fatigue: endurance times and spectral changes in the electromyogram during the production of sustained bite forces.

The purpose of this experiment was to determine if the characteristics of fatigue observed in the limb muscle system are also evident in the muscles of mastication, specifically, the masseter and temporalis. Surface electrodes were placed bilaterally over the masseter and temporalis muscles of 10 adults. Each subject was instructed to maintain maximal and six levels of submaximal incisal bite forces for as long as possible. The power density spectrum of the electromyographic signals for each muscle was calculated at the onset and failure of the task. The decrease in endurance time with an increase in bite force followed a pattern similar to that in limb muscles, and each muscle was characterized by a consistent reduction in the mean power frequency of the power density spectrum and a variable change in r.m.s. power. The variability of changes in r.m.s. power (which is inconsistent with changes found in the limb muscles) was explained in terms of either changes in motor-unit firing rate or the muscle's relative contribution to the generation of bite force. The analyses also demonstrated a curvilinear relationship between bite force and r.m.s. power, but no relationship between bite force and the mean power frequency of the power density spectrum.

Adult↗
PubMed1990

Vitamin A deficiency increases noise susceptibility in guinea pigs.

The effect of vitamin A deficiency in guinea pigs on noise-induced temporary threshold shift (TTS) was evaluated after short (15 min) acoustic overstimulation with a moderate (90 dB) broad-band white noise. Some guinea pigs were fed ad libitum a purified diet deficient in vitamin A (VAD group) until biochemical signs of deficiency occurred. A second, control group (VA group) received the same diet as well as 100 IU vitamin A daily by pharyngeal tube. Cochlear potentials were recorded by special computerized equipment using implanted electrodes. Before acoustic stimulation, a baseline value was determined with a test stimulus [90 dBA (A-filter according to usual DIN instructions)] corresponding to that for TTS measurements. Noise-induced changes were determined by calculating the changes in latency and amplitude of the N1-signal of the compound action potential (CAP) at various times (1, 3, 5, 7, 11 min) after termination of acoustic stimulation in comparison with baseline values. Statistical analysis of the CAP data showed that the VAD group had significantly smaller amplitudes and increased latency of the N1-potential after acoustic stimulation and that the VA group did not show a significant change in amplitude or latency. The reduction in N1-amplitude and N1-latency in the VAD group reflects changes in inner ear hair cell activity. We conclude that vitamin A deficiency increases the sensitivity of the inner ear to noise and that this increased sensitivity increases the probability of noise-induced hearing loss.

Acoustic Stimulation↗
PubMed1990

Voluntary facial action generates emotion-specific autonomic nervous system activity.

Four experiments were conducted to determine whether voluntarily produced emotional facial configurations are associated with differentiated patterns of autonomic activity, and if so, how this might be mediated. Subjects received muscle-by-muscle instructions and coaching to produce facial configurations for anger, disgust, fear, happiness, sadness, and surprise while heart rate, skin conductance, finger temperature, and somatic activity were monitored. Results indicated that voluntary facial activity produced significant levels of subjective experience of the associated emotion, and that autonomic distinctions among emotions: (a) were found both between negative and positive emotions and among negative emotions, (b) were consistent between group and individual subjects' data, (c) were found in both male and female subjects, (d) were found in both specialized (actors, scientists) and nonspecialized populations, (e) were stronger when the voluntary facial configurations most closely resembled actual emotional expressions, and (f) were stronger when experience of the associated emotion was reported. The capacity of voluntary facial activity to generate emotion-specific autonomic activity: (a) did not require subjects to see facial expressions (either in a mirror or on an experimenter's face), and (b) could not be explained by differences in the difficulty of making the expressions or by differences in concomitant somatic activity.

Adult↗
PubMed1992

A successful computerized protocol for clinical management of pressure control inverse ratio ventilation in ARDS patients.

We have developed a computerized protocol that provides a systematic approach for management of pressure control-inverse ratio ventilation (PCIRV). The protocols were used for 1,466 h in ten around-the-clock PCIRV evaluations on seven patients with severe adult respiratory distress syndrome (ARDS). Patient therapy was controlled by protocol 95 percent of the time (1,396 of 1,466 h) and 90 percent of the protocol instructions (1,937 of 2,158) were followed by the clinical staff. Of the 221 protocol instructions, 88 (39 percent) not followed were due to invalid PEEPi measurements. Compared with preceding values during CPPV, the expired minute ventilation was reduced by 27 percent during PCIRV while maintaining a pH that was not clinically different (mean difference in pH = 0.02). There was no difference in the PaO2, PEEPi, or the FIO2 between PCIRV and CPPV. The PEEP setting was reduced by 33 percent from 9 +/- 0.05 to 6 +/- 0.6 and the I:E ratio increased from 0.64 +/- 0.04 to 2.3 +/- 0.10. Peak airway pressure was reduced by 24 percent (from 59 +/- 1.5 to 45 +/- 0.6) and mean airway pressure increased by 27 percent (from 22 +/- 0.8 to 28 +/- 0.6) in PCIRV. Right atrial and pulmonary artery pressures were higher and cardiac output lower in PCIRV but blood pressure was unchanged. The success of this protocol has demonstrated the feasibility of using PEEPi as a primary control variable for oxygenation. This computerized PCIRV protocol should make the future use of PCIRV less mystifying, simpler, and more systematic.

Adult↗
PubMed1991

Tempo, stress, and vowel reduction in American English.

Two processes that affect the acoustic characteristics of vowels, namely, phonological and phonetic vowel reduction are discussed. Phonological vowel reduction applies to unstressed vowels. Phonetic vowel reduction is supposed to apply to all vowels and be caused by fast speech rates, context, as well as lack of stress. In this experiment, the effects of changes in stress and in rate of speech (tempo) on the acoustic characteristics of American English monophthongal, nonretroflex vowels were examined. Four male and four female native speakers produced these vowels in two contexts, [h_d] and [b_d], in a carrier sentence, under four conditions of tempo stress (slow-stressed, slow-unstressed, fast-stressed, and fast-unstressed). Measurements of duration and fundamental frequency showed that the subjects did, in fact, vary tempo and stress as instructed. The effect of a change in stress on vowel duration was found to be slightly larger than that of a change in tempo. The putative vowel portion of each utterance was analyzed, formant tracks were obtained, and these were plotted in an auditory-perceptual space [J.D. Miller, J. Acoust. Soc. AM. 85, 2114-2134 (1989)]. These plots served to determine the part of the utterance that could, in most cases, be considered its steady state. For each utterance, an average of the coordinates of this steady-state portion was taken and was used to represent the utterance as a point in the auditory-perceptual space. The distance of these data points from the point representing the acoustic characteristics of a vowel produced by a neutral vocal tract was used to determine the magnitude of phonetic vowel reduction caused by faster tempo and less stress, relative to the slow-stressed condition. Although the results indicate that tempo and stress may not have a major influence on the distances of individual vowels from the neutral point, the size of the vowel space overall was affected. The vowel space was largest for the slow stressed condition and smallest for the fast unstressed condition. In addition, several vowel classifications schemes were tested using linear discriminant analysis, and the one proposed by Miller (1989) performed better than other combinations of fundamental frequency and the first three formants.

Adult↗
PubMed1989

An electrophysiological investigation of the spatial distribution of attention to colored stimuli in focused and divided attention conditions.

In the present experiment ERPs were recorded to colored stimulus bars (red or blue) which were randomly presented at one out of eight different spatial locations on a visual display. The locations were situated on a hemi-circle around the fixation point, with four locations lying in each visual half-field. The subjects were instructed to attend to one stimulus location (the most peripheral left or right location: the relevant location) in a focused attention condition and to all four locations within the same visual half-field in a divided attention condition, and were instructed to respond to stimulus bars in one color presented at the relevant location(s). In the focused attention condition, spatial attention resulted in early positivity in the P1 latency range (ca. 100-175 ms), followed by a prolonged negativity in the N1, P2, and N2 latency range (ca. 175-350 ms). These effects generalized to locations in the same visual half-field as the relevant location. The effect of attending and responding to the target color consisted of a number of different effects. An early anterior positivity, occipital negativity was observed for the relevant location and for locations in the same visual half-field as the relevant location, but not for the locations in the opposite visual field. A later central negativity (N2b) appeared to be confined to the relevant location and one location adjacent to it. Finally, a late parietal positivity (P3b) was exclusively evoked by target stimuli at the relevant location. In the divided attention condition, the ERPs evoked by stimuli presented at each of the four locations within the relevant visual half-field showed increased early positivity (enhancing P1 amplitude) as compared to the ERPs to stimuli in the opposite (irrelevant) visual half-field. The early color selection effect was also found to all stimuli within the relevant half-field, but the N2b component was evoked both by stimuli within the relevant half-field and by stimuli at the location in the irrelevant half-field closest to the midline. The P3b was present to target stimuli at the three most lateral positions within the relevant half-field but it was absent to the relevant location closest to the midline. The data suggested that the attentional spotlight encompassed at least approximately 2 degrees in the focused attention condition, and an efficient selection by visual half-field in the divided attention situation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

Image data compression using a new floating-point digital signal processor.

A new dual-ported, floating-point, digital signal processor has been evaluated for compressing 512 and 1,024 digital radiographic images using a full-frame, two-dimensional, discrete cosine transform (2D-DCT). The floating point digital signal processor operates at 49.5 million floating point instructions per second (MFLOPS). The level of compression can be changed by varying four parameters in the lossy compression algorithm. Throughput times were measured for both 2D-DCT compression and decompression. For a 1,024 x 1,024 x 10-bit image with a compression ratio of 316:1, the throughput was 75.73 seconds (compression plus decompression throughput). For a digital fluorography 1,024 x 1,024 x 8-bit image and a compression ratio of 26:1, the total throughput time was 63.23 seconds. For a computed tomography image of 512 x 512 x 12 bits and a compression ratio of 10:1 the throughput time was 19.65 seconds.

Algorithms↗
PubMed1991

PNM: a program for parametric and nonparametric mapping of multidimensional data.

A program named PNM is presented for the mapping of multidimensional data within a two-class classification problem. A novel mapping method is used for the purpose. The computing procedure implemented in the program is described in detail. Definitions and examples of the control instructions of the program are given at length. An application of PNM for classifier design concerning differential diagnoses of the cerebrovascular accident is presented. It confirms the efficiency of the program in solving classification problems of relatively large size on a small computer.

Brain Ischemia↗
PubMedDate not supplied

Computerized management of patient care in a complex, controlled clinical trial in the intensive care unit.

Acute respiratory distress syndrome (ARDS) is often not responsive to conventional supportive therapy and the mortality rate may exceed 90%. A new form of supportive care, extracorporeal carbon dioxide removal (ECCO2R), has shown a dramatic increase in survival (48%). A controlled clinical trial of the new ECCO2R therapy versus conventional continuous positive pressure ventilation (CPPV) is being initiated. Detailed care protocols have been developed by 'expert' critical care physicians for the management of patients. Using a blackboard control architecture, the protocols have been implemented on an existing hospital information system and will direct patient care and help manage the controlled clinical trial. Therapeutic instructions are automatically generated by the computer from data input by physicians, nurses, respiratory therapists, and the laboratory. Preliminary results show that the computerized protocol system can direct therapy for acutely ill patients.

Blood Gas Analysis↗
PubMed1991

Bayesian image reconstruction for emission tomography incorporating Good's roughness prior on massively parallel processors.

Since the introduction by Shepp and Vardi [Shepp, L. A. & Vardi, Y. (1982) IEEE Trans. Med. Imaging 1, 113-121] of the expectation-maximization algorithm for the generation of maximum-likelihood images in emission tomography, a number of investigators have applied the maximum-likelihood method to imaging problems. Though this approach is promising, it is now well known that the unconstrained maximum-likelihood approach has two major drawbacks: (i) the algorithm is computationally demanding, resulting in reconstruction times that are not acceptable for routine clinical application, and (ii) the unconstrained maximum-likelihood estimator has a fundamental noise artifact that worsens as the iterative algorithm climbs the likelihood hill. In this paper the computation issue is addressed by proposing an implementation on the class of massively parallel single-instruction, multiple-data architectures. By restructuring the superposition integrals required for the expectation-maximization algorithm as the solutions of partial differential equations, the local data passage required for efficient computation on this class of machines is satisfied. For dealing with the "noise artifact" a Markov random field prior determined by Good's rotationally invariant roughness penalty is incorporated. These methods are demonstrated on the single-instruction multiple-data class of parallel processors, with the computation times compared with those on conventional and hypercube architectures.

Algorithms↗
PubMed1989

A review of medical education and medical informatics.

Physicians have considerable difficulty collecting and interpreting information from patients, dealing with the uncertainties associated with diagnosing and treating their patients, communicating precisely with one another, keeping up to date, and applying recommended procedures when indicated. Some of the advances in information technology may help physicians to manage information more effectively through more accessible, validated clinical indexes, data bases of diagnostic test characteristics, computerized audits of clinical activities with feedback, expert systems, on-line access to the medical literature, and other tools of medical informatics. Medical educators can catalyze this process by facilitating the introduction of information technology into academic clinical settings so that students can learn its use first-hand and by promoting the evolution of this and other aspects of medical informatics, a new discipline dedicated to the solution of information problems in health care. The potential roles for computer-aided instruction and centralized computer laboratories in medical schools are much less clear.

Canada↗
PubMed1977

Roentgen-tele-data: a radiodiagnostic recording system.

A radiodiagnostic data-handling system with telephones connected to the hospital exchange is described. Time, date, and location of examination are automatically recorded. The system can deliver spoken instructions from the computer and warns if data are not valid. Diagnosis, their degree of verification, and cases of special interest are added at display terminals. Codes, equipment, and output are described. Costs represent 1% of the department's expenditures. Future plans include a booking sytem, rapid access, and on-line connection to the main data system.

Computers↗
PubMed1990

Increase of interproximal bone density after subgingival instrumentation: a quantitative radiographical study.

Ten interproximal sites, with periodontal pockets deeper than 5 mm and showing loss of bone on standard dental radiographs, were treated by subgingival instrumentation in 10 patients properly motivated and given thorough hygiene instructions. The index of gingival inflammation, the plaque index, the degree of mobility, the depth of the pockets, and the loss of attachment were measured before starting the treatment, and 2 months, 6 months, and 1 year after treatment. Standardized reproducible radiographs of the 10 sites were taken by using a recently developed paralleling instrument before treatment, immediately after and 2 months, 6 months, and 1 year afterwards. The density of the interdental bone was measured on the radiographs by a computer assisted densitometric technique at three levels of the interdental septum: the most occlusal or "superficial" level; the "deep" level, arbitrarily chosen 1.5 mm below; and the "control" level, in a much deeper area of interproximal bone. As further control, the density of the superficial crestal bone was also followed in 5 healthy untreated sites from 5 of the patients. As expected, a significant improvement of the clinical parameters was observed during the year following therapy. The results of the radiographical analysis showed statistically significant increases of both the superficial and deep average densities of interproximal bone at 6 months and 1 year after treatment. The superficial bone density was, on the average, 13% higher at 6 months and 16% higher at 1 year, as compared to that measured immediately after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1992

Fulfilling the promise: implementing IAIMS at Georgetown University.

Predictions are that the integration of multiple information systems of a medical center will change the way doctors work and practice medicine in the future. Several major steps must be taken by an institution to make this a reality. The IAIMS program sponsored by the NLM is designed to achieve integration of resources in the medical center environment. The purpose of the IAIMS project at Georgetown is to develop a medical decision support system by bringing together multiple sources of information that reside on disparate computers and different database systems. This immense and complex task is described in this paper from an organizational, academic and technical perspective. Georgetown is developing a Biotechnology and Biomedical Knowledge Network which includes several informational and clinical databases, a variety of scholar workstations, instruction on use of computers, a campus-wide network with local area network nodes and a modular approach to systems integration. The IAIMS project is spearheaded by the medical library which has enabled a broad body of medical center users to benefit directly from new, dynamic services.

Academic Medical Centers↗
PubMed1992

Health status measurement. Implementation strategies.

The creation of valid instruments of health status measurement does not guarantee their use in the clinical setting. Traditional continuing medical education has not been shown to effect physician behavioral change. Examination of the literature on the dissemination of new technology underscores the need for the acceptance and use of new methods by local opinion leaders whose behavior serves as a model for their colleagues. Since health status measurement will require a new way of evaluating the patient visit and the creation of new provider behaviors, widespread implementation will require the recruitment of local clinical leaders to serve as spokesmen for reconsideration of office care procedures. Advocates of health status measurement should seize on a variety of opportunities to disseminate their work. Medical school curricula in courses such as physical diagnosis could expose different approaches to the patient encounter to a new generation of physicians in a fairly painless and seamless manner. Academic practice plans, by virtue of their increasing trend to centralization, could commit to patient-oriented data collection--if not for instructional purposes, then for the overall health of the delivery system. The instruction of nurses and paraprofessionals in the collection of these data could expand the measures and help drive the system when physicians are not embracing the technology. There is need to exploit the enhanced capacity of computer hardware and software in the service of efficient data collection and trend analysis of health status.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1991

Medical Practice Support System. A medical practitioner's multimedia workstation.

The United States Navy has developed a computer based Medical Practice Support System (MEPSS) intended for use by medical practitioners working in isolated situations. The system, now being tested in operational settings, emphasizes inexpensive, easily obtained off-the-shelf hardware and specially developed, readily implemented software to provide users with: 1) medical record keeping, 2) an electronic medical library, 3) interactive video instruction programs suitable for continuing medical education, 4) computer based medical diagnosis and treatment assistance, and 5) electronic communications with other facilities. This demonstration emphasizes a user based developmental approach, integration of diverse systems under a single user interface, and portable hardware. The resulting system makes medical information needed by practitioners instantly available at the time of a patient encounter, whenever and wherever that encounter may occur. Making clinically valuable information immediately available, MEPSS demonstrates how practitioners can use computers to help their own efforts to improve patient care quality and efficiency.

Decision Making, Computer-Assisted↗
PubMedDate not supplied

A real-time analysis of a transplantation program with a personal computer.

This study concerns the use of commercial software (a spreadsheet combined with database and graphic functions) to analyze data on kidney transplantation. The program consists of a section containing (macro) instructions, a section for entering data, a database, a set of spreadsheets (one for each field) with which the statistical calculations and summary tables are executed, and a set of diagrams for the final visual output. Three kinds of data are made available: descriptive statistics, actuarial survival rates, and risk factor evaluation. The program can analyze the importance of the variables considered and estimate the effect of a therapeutic or diagnostic maneuver.

Computer Systems↗