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Biomedical subjects

D R McNeal

Publications and source records attributed to D R McNeal.

At least 19 recordsLinked to original sources
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↗
PubMed1976

Electrical stimulation and feedback training: effects on the voluntary control of paretic muscles.

The carry-over effect of gait-synchronized stimulation of the peroneal nerve on voluntary dorsiflexion of the paretic foot was evaluated in hemiplegic patients. The influence of providing audiovisual feedback of performance on voluntary control was also evaluated. Each patient received three test sessions separated at least one week apart. In each session, measurement of isometric torque from voluntary effort was repeated four times: before, and at 0, 30 and 60 minutes after a 20-minute walk period. Session 2 involved both peroneal stimulation during walking and performance feedback during voluntary efforts. Session 1 had stimulation only. Session 3 had feedback only. The results were inconsistent among the patients. Where increase of voluntary dorsiflexion was obtained, it was more a consequence of performance feedback than peroneal stimulation. General problems of using isometric torque produced by voluntary dorsiflexion as a measure of the carry-over effect are discussed.

Adult↗
PubMed1975

A comparison of the effectiveness of the "Toothkeeper" and a traditional dental health education program.

A study was made of the effectiveness of two dental health education programs in an elementary school in Flint, Michigan. Following stratification by grades, random assignments of students were made by classrooms to either the Toothkeeper group or a "Traditional" group. No control groups were employed. Separate in-service training workshops were attended by the classroom teachers according to the education program to which they had been randomly assigned. An intensive 16-week program was conducted by the classroom teachers following the guidelines of the two programs. Dental examinations which included an assessment of plaque and gingivitis scores were conducted on all participants at baseline, at the end of 16 weeks, and at the conclusion of the school year, some seven months after the initiation of the program. Only minimal reductions in plaque scores were observed with either program and little comparative difference was found in the two programs at the end of the evaluation period. The Toothkeeper group experienced a somewhat greater reduction in plaque scores than the "Traditional" group during the intensive 16-week phase of the study, but these scores worsened from this time to the end of the school year. Gingivitis scores demonstrated more improvement than the reductions in plaque scores would indicate and may be related to the confounding factor of large numbers of children receiving dental treatment, especially prophylaxes during the course of this study. Differences in reductions in gingivitis between the two programs were not meaningful clinically.

Dental Devices, Home Care↗
PubMed1975

Peroneal nerve conduction velocity after chronic electrical stimulation.

The effects of electric stimulation on nerve conduction velocity of the peroneal nerve via surgically implanted electrodes was evaluated in a group of nine hemiplegic patients. After a mean duration of 25 months nerve conduction velocity averaged 47.3 meters/sec in the uninvolved and 46.1 meters/sec in the stimulated (paretic) extremity. In a control group of ten hemiplegic subjects who did not receive stimulation, nerve conduction velocity averaged 43.1 meters/sec in the hemiplegic leg, and 41.3 meters/sec in the uninvolved leg. These differences were not statistically significant. Maximum dorsiflexion strength was increased in all patients following chronic stimulation.

Ankle↗
PubMedDate not supplied

Experience with implanted electrodes.

Implant units, manufactured by Medtronic, Inc., have been implanted in 31 patients for treatment of drop-foot. The principal problem encountered in this series was inflammatory reaction. This was observed in seven patients, and was serious enough in five to require removal of the implant. On the positive side, there have been no failures of the implanted equipment for periods of up to 7.3 years, although there is currently a question on one patient. There has also been no documented damage to the nerve from chronic stimulation. Fine wire elctrodes have been implanted intraneurally in a series of animals and in three patients. Preliminary results look encouraging, and this approach seems to hold considerable promise for a new generation of electrode design.

Amputees↗
PubMedDate not supplied

Spinal cord monitoring using evoked potentials recorded from feline vertebral bone.

A new recording method for continuous spinal cord monitoring has been developed at Rancho Los Amigo Hospital. Using peripheral nerve stimulation, spinal evoked potentials (SEPs) are recorded from cancellous bone of spinous processes. This neurologically noninvasive technique provides a highly reproducible and consistent signal, unaffected by biologic noise and surgical handling of the spinal column. Moreover, the evoked response is extremely sensitive to changes in functional integrity of the spinal cord. In experimental spinal cord injuries, produced by localized distraction of the spine, changes of the evoked responses were well correlated with the change in spinal cord function.

Animals↗