PubMed Health⌕ Search

Biomedical subjects

D R McNeal

Publications and source records attributed to D R McNeal.

At least 19 recordsLinked to original sources
PubMed1999

Work problems and accommodations reported by persons who are postpolio or have a spinal cord injury.

A number of studies have documented early functional declines in persons with a disability. The purpose of this study was to document (1) whether employees who are aging with their disability have experienced new work problems as a consequence of functional declines and (2) whether their work problems are being accommodated adequately. Ninety-six individuals with a disability (50 who are postpolio and 46 who had a spinal cord injury) were interviewed by phone. Each had worked at least 5 years postonset and was either currently working or unemployed for less than 5 years at the time of the interview. Forty-nine of the 50 persons who are postpolio reported they had experienced functional declines in recent years, and 41 of the 50 rated the severity of their disability greater than it was when they first began working. As a result of the functional declines they had experienced, most (90.9%) of their work problems were new and would not have been significant problems for them when they first began working. The situation was very different for the group with spinal cord injuries. Only a few members of that group had experienced functional declines that were causing new problems at work. A total of 480 work problems were reported by study participants. Three out of every eight problems did not have an accommodation satisfactory to the employee. The primary reason why a satisfactory solution was not provided was that no accommodation had been identified. Employers were generally supportive of the employee's need for accommodation; they paid for 59.1% of the accommodations that had a cost and refused to provide an accommodation for only 18 of the 480 problems.

Activities of Daily Living↗
PubMed1995

Is body powered operation of upper limb prostheses feasible for young limb deficient children?

The investigators measured efficiencies of body powered prehensors and cable control components of prostheses available for young children. Results indicated that the cable control systems and hook type prehensors have moderate to high efficiencies, but children's body powered hands have very low efficiencies. Measures of arm and shoulder strength of 3-5 year-old limb deficient children, both on the limb deficient and sound sides, were less than that reported in the sound sides, were less than that reported in the literature for normal children. The findings were examined in relation to children's strength available compared with prosthesis strength requirements. The comparison demonstrates a way to establish measurable efficiency targets for new prehensor designs. The article includes detailed findings on children's strength, and findings on efficiencies of the prehensors and cable control systems of children's upper limb prosthses. Sample calculations may be useful to future designers of body powered prehensors for young children. A more efficient body powered hand is especially needed. Preliminary calculations indicate that the use of currently available children's voluntary opening (VO), body powered hands is not feasible, given the low strength of young limb deficient children and the low efficiencies of the VO hands. The use of voluntary closing (VC) hands may be feasible but remains to be tested.

Age Factors↗
PubMed1991

Motor point delineation of the gluteus medius muscle for functional electrical stimulation: an in vivo anatomic study.

The purpose of this study was to delineate the motor point region of the gluteus medius muscle to aid in placing epimysial electrodes for functional electrical stimulation. Seven surgically dissected gluteus medius muscles were studied in five patients. The lateral surface of the muscle was sequentially probed with an electrical stimulator. The motor point region, which responded maximally to an applied electric current, was located on the posterolateral aspect of the muscle, adjacent to the superior margin of the piriformis, 3 cm lateral to the greater sciatic notch; it was rectangular or oval, measuring approximately 3.5 cm by 3.0 cm. The mean threshold current that produced a contraction was 14 mA (range = 2 to 26 mA). The mean minimum current required to produce a maximum contraction was 34 mA (range = 11 to 60 mA). This information provides guidelines for the placement of electrodes for functional electrical stimulation of this deeply situated muscle, and it provides electrical stimulation parameters required for adequate muscle activation.

Adult↗
PubMed1990

The Pew National Dental Education Program at the University of Florida College of Dentistry.

The University of Florida College of Dentistry is located in a dynamic environment. Socially, economically, and demographically, the state of Florida manifests changes reflective of the entire nation, i.e., increasing numbers of elderly and minorities, a fluctuating, diversified economy, and altered cultural values. The explosive growth unique to this state has both positive and negative implications for all aspects of its culture and economy. The college resides in a maturing, research-oriented university facing vigorous competition from other major universities in the state. Within the Health Science Center, the college was occupied during the first decade of its existence with development of an innovative curriculum, and now it must turn its attention to a new emphasis on research and service. A process of strategic planning was conducted at the University of Florida College of Dentistry from January 1986 through June 1987. Four consultant groups representing the college, the university, organized dentistry in Florida, and outside consultants, were guided by a steering committee in a thorough evaluation of the external and internal environment of the institution.(ABSTRACT TRUNCATED AT 250 WORDS)

Education, Dental↗
PubMed1989

An extramural dental education program in a rural setting in Florida.

An extramural dental education experience which is a required component of the University of Florida College of Dentistry is described. The program, established in 1977, is conducted on a contractual basis between the college and the Lafayette-Suwannee Rural Health Corporation, Inc., the governing body of the Dental Center clinic located in the town of Mayo, Florida, which is 65 miles from the dental school. The program has brought high quality comprehensive dental care to a previously underserved population. Dental students are provided with experiences that enhance social sensitization, and that are perceived by them as a help in bridging the gap between dental school and dental practice after graduation. The program has made valued contributions to the education, research, and service components of the dental school's mission.

Clinical Competence↗
PubMed1989

Recruitment data for nerve cuff electrodes: implications for design of implantable stimulators.

Recruitment characteristics of nerve cuff electrodes implanted in four cats for five months were measured. Monopolar, bipolar, and tripolar configurations were considered. Approximately twice the current was required to achieve a given response using the tripolar configuration as compared with monopolar stimulation. Bipolar stimulation also required more current than monopolar stimulation. Using the recruitment data, a number of strategies for modulating muscle tension were considered. It was shown that both pulse amplitude and pulse duration should be software-selectable to achieve adequate control of muscle tension when using either pulse amplitude modulation or pulse duration modulation. When using pulse amplitude modulation, it was found to be desirable to operate at a low pulse duration in the high end of the allowable range for pulse amplitude. For pulse duration modulation, one should operate at a low pulse amplitude in the high end of the allowable range for pulse duration. The effect of pulse amplitude and pulse duration step size on the maximum step change in muscle tension and the linearity of the recruitment curves were examined. The use of logarithmic steps in the modulation parameter was examined and was shown to result in improved controllability and linearity.

Animals↗
PubMed1989

A four-channel IBM PC/AT compatible biphasic pulse generator for nerve stimulation.

An IBM PC/AT compatible four-channel biphasic pulse generator has been developed to assist in functional electrical stimulation (FES) related research. Each channel uses a bipolar 12-bit digital-to-analog converter (DAC) to generate biphasic voltage pulses between +/- 5 VDC and three 16-bit timers to control first, second, and interphase durations. Two vectored interrupt generators are available for precise pulse timing control. Potential uses of this device include FES research, the characterization of the recruitment properties of percutaneous electrodes in multichannel stimulation systems, or as a subassembly in commercial medical devices requiring electrical simulation in an IBM PC/AT platform.

Electric Stimulation↗
PubMed1989

Open-loop control of the freely-swinging paralyzed leg.

An experimental model has been used to study issues that are relevant to the use of electrical stimulation to help paralyzed individuals walk. Modulated stimulation sequences for the quadriceps muscles were manually selected using an iterative trial-and-error procedure to cause the knee angle to follow a specific movement pattern (desired trajectory). Four paraplegic subjects were tested before and after an eight-week program in which the quadriceps were exercised daily with electrical stimulation. It was found that 12.6 +/- 2.9 iterations were required to approximate the desired trajectory. The average error of the final match between the actual and desired trajectories was 2.1 degrees +/- 0.7. Repeated responses were extremely consistent; the average difference between successive trials was less than 1 degree in 81 percent of the trials. When the stimulation sequence was repeated every 3 s for 50 cycles, however, there was a progressive degradation in the response, even in exercised legs, that demonstrated the limitations of open-loop control. Stimulus modulation envelopes for all four subjects were similar in shape (although varied in amplitude) indicating that the iterative process can be shortened by starting with an "average" modulation envelope. Stimulation sequences achieved accurate matches of the desired trajectory on subsequent days when adjusted by a simple gain factor. The relevance of these results to multichannel control of walking is discussed.

Adult↗
PubMed1989

Standing balance training: effect on balance and locomotion in hemiparetic adults.

The effects of balance retraining on standing balance and locomotor performance were examined in postacute hemiparetic adults. Balance during habitual and instructed-even standing, as well as locomotor performance, were measured before and after a three- to four-week treatment period. Two groups of 21 matched subjects participated in physical therapy. One group received standing balance training with a specially designed feedback device that provided dynamic visual information about relative weight distribution over the paretic and nonparetic limb. Subjects trained with the feedback device showed significantly better static standing symmetry than did subjects who did not receive augmented feedback, p less than .05. Although both groups improved significantly in gait velocity, cadence, stride length, and cycle time, p less than .01, the initially identified asymmetrical locomotor pattern appeared to be only minimally affected by the standing balance training. Results indicated that although standing balance and locomotor control mechanisms may be highly interrelated, a reduction in standing balance asymmetry does not necessarily lead to a concomitant reduction in the asymmetrical limb movement patterns associated with hemiparetic locomotion.

Arm↗
PubMed1988

Effects of joint angle, electrodes and waveform on electrical stimulation of the quadriceps and hamstrings.

Isometric twitch moments of the quadriceps and hamstrings were recorded in 20 normal subjects at 40 cells of a superimposed grid. Results were compared at 15, 45, and 75 degrees of knee flexion. Bipolar stimulation at 6 pairs of cells was performed to determine the effect of electrode size, waveform, and polarity on moments. The quadriceps had one region of excitability over the femoral nerve and a second broader region of excitability over the muscle mass. Neither location was significantly affected by knee flexion. Regions of excitability for the hamstrings demonstrated more individual variation and were affected by knee angle. Electrode size had little effect on moments produced with monopolar or bipolar stimulation. When monophasic waveforms were used, reversing polarity generally caused changes in moments of greater than 20%, whereas polarity had no significant effect when using biphasic waveforms. Moments produced with biphasic waveforms were always greater (by 20-25%) when compared with monophasic waveforms. During monopolar, monophasic stimulation, the anode, often termed the "indifferent" electrode, produced nearly 70% of the moment produced by the cathode.

Adult↗
PubMed1988

A 3-year clinical trial to compare efficacy of dentifrices containing 1.14% and 0.76% sodium monofluorophosphate.

A 3-yr daily supervised toothbrushing study with a double blind design was conducted to evaluate the anticaries effectiveness of a 1.14% sodium monofluorophosphate (MFP) dentifrice (1500 ppm F) compared to a 0.76% MFP dentifrice (1000 ppm F). This study began with nearly 4000 children, primarily aged 8-11, in grades 3-5, residing in a nonfluoridated community in Florida. A total of 2415 children completed 3 yr of the study, representing 61% of the children who began the study. The results indicate a statistically significant (P less than 0.001) anticaries benefit was derived over a 3-yr period from the use of the higher fluoride dentifrice (1500 ppm F) when compared to the positive control (1000 ppm F). Percent reductions in mean dental caries increments were 20.9%, 22.1%, 21.8%, 24.3%, and 35.2% for DMFT, DFT, DMFS, DFS, and DFS Interproximal, respectively.

Adolescent↗
PubMed1988

Effects of waveform on comfort during neuromuscular electrical stimulation.

Electrical stimulation is a commonly used clinical tool, but subject and patient comfort is still a major problem retarding its widespread application. Stimulus waveform in combination with pulse duration can play a major part in subject comfort. An asymmetric balanced biphasic square waveform was perceived as comfortable and was clinically effective in stimulating wrist flexor and extensor muscles. Subjects preferred the square waveforms over a paired spike monophasic waveform. In the larger quadriceps muscle group, a symmetric biphasic square wave was perceived as more comfortable than either a monophasic paired spike or any of three medium frequency waveforms. There seemed to be, however, a small subpopulation of subjects who consistently preferred the medium frequency waveforms. Medium frequency stimulation should be tried for those patients who have considerable difficulty adapting to the sensory input inherent with the use of surface electrical stimulation.

Adult↗
PubMed1986

Response of single alpha motoneurons to high-frequency pulse trains. Firing behavior and conduction block phenomenon.

Studies were conducted on 25 cats to document the discharge rates of alpha motoneurons during stimulation of the sciatic nerve at frequencies from 100 to 10,000 pulses per second (pps). In addition, the feasibility of using high-frequency pulse trains to block the conduction of action potentials was investigated. Two cuff electrodes were placed around the proximal portion of the left sciatic nerve, and recordings of antidromic potentials were taken from single fibers of the L7 ventral root. When stimulating through the more proximal electrode, discharge rates were generally equal to or were subharmonics of the stimulation rate up to 1,000 pps. Firing often decreased in rate during 3-min runs. At 2,000-10,000 pps, fibers responded briefly at rates of several hundred per second but stopped firing within seconds after stimulus initiation. After cessation of response to the high-frequency pulse train, action potentials generated at 50 pps at the more distal electrode did not propagate to the recording electrodes. The 'electrical block' so induced was maintained for up to 20 min, and recovery following termination of the pulse train was complete within 1 s.

Action Potentials↗