PubMed Health⌕ Search

Biomedical subjects

L L Baker

Publications and source records attributed to L L Baker.

At least 19 recordsLinked to original sources
PubMed2001

Electromyographic activity of selected trunk muscles during dynamic spine stabilization exercises.

OBJECTIVES: To compare the electromyographic activity of the trunk flexors and extensors during 2 spine stabilization exercises and to evaluate the changes in muscle activity with increasing levels of exercise difficulty. DESIGN: Descriptive study. SETTING: Research laboratory. PARTICIPANTS: Twelve healthy subjects without history of lower back pain. INTERVENTION: Subjects were instructed how to perform the Dying Bug and the Quadruped exercises. Electromyographic and motion data were recorded from each muscle group during maximum voluntary isometric contraction (MVIC). MAIN OUTCOME MEASURES: Surface electromyographic recordings of the erector spinae, rectus abdominus, abdominal oblique, and gluteus maximus muscles. RESULTS: During the Dying Bug exercise, the trunk flexors (rectus abdominus, abdominal oblique) were equally active and demonstrated proportional increases in electromyographic activity with increasing level of exercise difficulty. In the Quadruped exercise, significantly greater electromyographic activity was observed in the abdominal oblique compared with the rectus abdominus; however, abdominal oblique activity did not change with increasing level of difficulty. The erector spinae and gluteus maximus demonstrated a significant level effect and were most active during elevation of the ipsilateral leg. At no point did activity of any of the muscles studied exceed 41% of the MVIC. CONCLUSIONS: Results indicated the Dying Bug exercise predominantly recruited the abdominal musculature, while greater activity was observed in the trunk and hip extensors during the Quadruped exercise. The relatively low levels of electromyographic activity observed in both exercises suggests that the intensity of muscle recruitment is not likely sufficient to provide a strengthening effect in healthy subjects.

Abdominal Muscles↗
PubMed1997

Effects of electrical stimulation on wound healing in patients with diabetic ulcers.

OBJECTIVE: To evaluate the effects of two stimulation waveforms on healing rates in patients with diabetes and open ulcers. The hypothesis was that stimulus waveforms with minimal polar characteristics would provide significant healing for this patient sample. RESEARCH DESIGN AND METHODS: This was a prospective study that enrolled 80 patients with open ulcers. Patients received stimulation with either an asymmetric biphasic (A) or symmetric biphasic (B) square-wave pulse. Amplitudes were set to activate intact peripheral nerves in the skin. Two other groups received either very low levels of stimulation current (MC), or no electrical stimulation (C). When combined these groups were referred to as the control group. Treatment was carried out daily until the wound healed, the patient withdrew from the study, or the physician changed the overall wound management program. Average healing rates were calculated from weekly measures of the wound perimeter and were used for statistical comparison through a one-way analysis of variance. RESULTS: Stimulation with the A protocol significantly increased the healing rate, enhancing healing by nearly 60% over the control rate of healing. Stimulation with the B protocol did not increase the healing rate when compared with control subjects. CONCLUSIONS: Electrical stimulation, given daily with a short pulsed, asymmetric biphasic waveform, was effective for enhancement of healing rates for patients with diabetes and open ulcers.

Adult↗
PubMed1996

Atlanto-axial subluxation and cervical osteomyelitis: two unusual complications of adenoidectomy.

Grisel's syndrome (atlanto-axial subluxation) and cervical osteomyelitis are two unusual complications of adenoidectomy. We present two patients; one with atlanto-axial subluxation following uncomplicated tonsillectomy and adenoidectomy, and one with cervical osteomyelitis following uncomplicated adenoidectomy. Both patients presented with persistent postoperative neck pain. Surgical intervention, as well as long-term intravenous antibiotics, was required. A high index of suspicion, as well as cervical spinal series with flexion-extension views, is necessary for diagnosis. Flexible nasopharyngoscopy and computed tomography of the cervical spine also aided in diagnosis and treatment planning. With early diagnosis and proper treatment, the prognosis is good. Neurologic sequelae were prevented in both of our patients.

Adenoidectomy↗
PubMed1995

Inter-hospital transport of neonatal patients on extracorporeal membrane oxygenation: mobile-ECMO.

OBJECTIVE: To describe the equipment, personnel requirements, training, management techniques, and logistic problems encountered in the design and implementation of a mobile extracorporeal membrane oxygenation (ECMO) program. DESIGN: This is a report of a technique for the transport of patients on ECMO and a description of our retrospective case series. SETTINGS: The study was conducted at a regional referral children's hospital and ECMO unit. PATIENTS: Thirteen neonatal medical patients with acute respiratory failure were transported with mobile-ECMO. RESULTS: Over a 24-month period, we transported 13 neonatal patients with mobile-ECMO. The reason for transport with mobile-ECMO was inability to convert from high-frequency ventilation (4 of 13), patient already on ECMO (1 of 13), and patient deemed too unstable for conventional transport (8 of 13). Eleven of the 13 patients were transported from other ECMO centers. Of the 13, 9 survived. No major complications during transport were reported for any of the patients. Follow-up data were available on all nine survivors of neonatal mobile-ECMO. Eight of these had normal magnetic resonance imaging scans of the brain; the ninth had a small hemorrhage in the left cerebellum. CONCLUSION: Our limited series shows that patients can be safely transported with mobile-ECMO. This program does not replace the early appropriate transfer for ECMO-eligible patients to an ECMO center.

Arkansas↗
PubMed1993

Mobile extracorporeal membrane oxygenation.

Transport of critically ill neonates in need of extracorporeal membrane oxygenation can be risky. Their extreme cardiorespiratory instability may delay or even preclude conventional transport to an extracorporeal membrane oxygenation center. We report the use of a UH-1 helicopter specially adapted for mobile extracorporeal membrane oxygenation support to transport a critically ill neonate.

Acidosis↗
PubMed1993

Trouble shooting the extracorporeal membrane oxygenator circuit and patient.

Patients requiring extracorporeal membrane oxygenation (ECMO) often become totally dependent on the mechanical life support. The Extracorporeal Life Support Organization (ELSO) reports 2486 incidents of mechanical complications in 5905 ECMO supports. To help decrease the number of mechanical complications, an active quality assurance program was initiated at our institution. This resulted in identification of only 14 incidents of mechanical complications in 100 patients (neonate, pediatric, adult, and cardiac). Techniques for dealing with problems such as loss of roller pump occlusion, changing out of the membrane lung or heat exchanger without interrupting ECMO support, venous air lock, tamponade, emergency transfusion, and other situations were generated into written policies and procedures. We routinely review and practice problem solving techniques with specific emphasis on monitoring patient hemodynamics and appearance. We conclude that written policies and procedures, "water drills," and continuing education can be beneficial in early recognition, intervention, and/or prevention of ECMO mechanical complications.

Blood Transfusion, Autologous↗
PubMed1991

Recent advances in MR imaging/spectroscopy of cerebral ischemia.

Recent advances in high-resolution MR imaging and multinuclear spectroscopy have stimulated studies of the functional relationships between tissue hypoperfusion, cellular energy depletion, and brain edema associated with cerebral ischemia. The very slow (microns/sec) random translational motion of water protons in various brain tissues and intracranial fluid compartments can now be assessed with MR diffusion imaging. More slowly diffusing protons in ischemic tissues can be differentiated from normal parenchyma, CSF, and flowing blood, enabling the detection and localization of ischemic regions within minutes of the onset of stroke. Perfusion imaging "snapshots," obtained in as little as 25 msec with echoplanar MR methods, permit the evaluation of tissue washin/washout kinetics of contrast agents in the microvasculature, and thus the quantification of brain perfusion on a regional basis. Also, delineation of major intra- and extracranial arterial and venous structures with MR angiography, acquired with two- or three-dimensional Fourier transformation techniques, has enabled accurate noninvasive assessments of vascular occlusive disease. Finally, improvements in MR spectroscopic techniques have facilitated investigations of metabolic regulation and bioenergetics in experimental animal models of cerebral ischemia, as well as in stroke patients. Combined MR imaging and spectroscopy will likely play an important role in differentiating reversibly from irreversibly ischemic brain tissues and in the investigation of various neuroprotective pharmaceuticals.

Animals↗
PubMed1991

Cerebrovascular disease.

The recent literature addresses the early detection of cerebrovascular disease using imaging techniques, metabolic assessment using spectroscopy, developments in quantitative analysis of brain blood flow, and new interventional techniques for aneurysm obliteration and carotid angioplasty.

Cerebral Angiography↗
PubMed1990

Structure-activity relationships for osteolathyrism. III. Substituted thiosemicarbazides.

Eight substituted thiosemicarbazides were assayed for their toxicity and teratogenicity using early embryos of Xenopus laevis. Results of the 96-h static tests on seven 4-position alkyl substituents were used for quantitative structure-activity relationship (QSAR) analyses, with thiosemicarbazide as the parent compound. The compounds induced malformations via the connective tissue defect osteolathyrism. Teratogenicity (log EC50) was negatively correlated with molar refractivity, suggesting that steric inhibitions were important in explaining the variations in biological activity due to changes in the 4-position substituent. It appeared that there were two separate modes of lethal action, one associated with the ring-containing substituents and the other with straight-chain substituents. However, QSARs were not developed for embryolethality (log LC50) or for the mortality/malformation index (LC50/EC50) due to the limited number of chemicals eliciting each lethal mode of action.

Animals↗
PubMed1990

Benign versus pathologic compression fractures of vertebral bodies: assessment with conventional spin-echo, chemical-shift, and STIR MR imaging.

Differentiation of benign from pathologic compression fractures of vertebral bodies was evaluated with magnetic resonance imaging in a prospective study of 53 patients. Twenty-six patients had 34 benign posttraumatic compression fractures. Twenty-seven patients had metastatic disease to the vertebral column and seven pathologic fractures. T1- and T2-weighted spin-echo (SE) sequences (1.5 T) were performed in all patients. A presaturation technique was used to obtain "fat" and "water" images to better assess the degree of normal fatty marrow replacement in fractured vertebrae. Short inversion-time inversion-recovery (STIR) images were also obtained. Discrimination between benign and pathologic compression fractures was generally possible with the SE sequences. Chronic benign fractures demonstrated isointense marrow signal intensity (SI), compared with that of normal vertebrae with all sequences. Pathologic fractures showed low SI on T1-weighted images and high SI on T2-weighted images. Fat images revealed complete replacement of normal fatty marrow, shown as absent SI in the involved vertebral body. Water and STIR images showed diffuse high SI in pathologic fractures, with STIR images having the highest contrast between abnormal and normal marrow. Acute benign compression fractures also demonstrated high SI on T2-weighted, water, and STIR images, but the SI was less pronounced and the pattern was generally more inhomogeneous than that of pathologic compressions. In general, fat images showed only partial replacement of normal fatty marrow by low SI, in contrast to the complete absence of marrow SI typical of pathologic fractures.

Adolescent↗
PubMed1990

Staging of Hodgkin disease in children: comparison of CT and lymphography with laparotomy.

Proper therapy for Hodgkin disease requires accurate staging of the disease. We compared the value of CT and lymphography with that of laparotomy for staging newly diagnosed Hodgkin disease in 46 children. The laparotomy revealed disease in one or more subdiaphragmatic sites in 46%. Correlation of the imaging studies with the laparotomy findings showed that lymphography has a greater sensitivity (80%) than does CT (40%) in detecting retroperitoneal lymph nodes. The sensitivity of CT in detecting splenic involvement was only 19%, presumably because of the small size of tumor deposits in involved spleens. Staging laparotomy altered the clinical stage in 37% of children, which resulted in a significant change of therapy in those patients. Although lymphography and, to a lesser degree, CT are useful for staging of Hodgkin disease, laparotomy continues to be the most important tool in choosing appropriate therapy for children with Hodgkin disease.

Adolescent↗
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↗
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

End-stage periventricular leukomalacia: MR evaluation.

A prospective study was performed to assess the capabilities of magnetic resonance (MR) imaging in evaluation of end-stage periventricular leukomalacia (PVL) in six children, aged 31-54 months, in whom PVL had been documented by neurologic ultrasonography during the neonatal period. Eight children of similar age (four premature infants and four full-term infants) with normal neurologic development served as controls. A characteristic triad of PVL abnormalities was seen on MR images: (a) abnormally increased periventricular white-matter signal intensity on the first and second echo images of a T2-weighted sequence (repetition time = 2,000-2,400 msec, echo times = 20 or 30 and 80 msec), most commonly observed in the trigone regions of the lateral ventricles bilaterally; (b) marked loss of periventricular white matter in these regions of abnormal signal intensity, predominantly in the periatrial regions; and (c) compensatory focal ventricular enlargement adjacent to regions of abnormal signal intensity. In patients with the classic periatrial distribution of PVL lesions, general correlation between the degree of neurologic impairment and the severity of MR abnormalities was demonstrated. MR imaging was useful in detecting subtle forms of PVL in cases in which neurologic damage was subclinical.

Encephalomalacia↗