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Biomedical subjects

A W Davidson

Publications and source records attributed to A W Davidson.

12 recordsLinked to original sources
PubMed2006

Autonomic dysfunction in dementia.

BACKGROUND: There are no studies of autonomic function comparing Alzheimer's disease (AD), vascular dementia (VAD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). AIMS: To assess cardiovascular autonomic function in 39 patients with AD, 30 with VAD, 30 with DLB, 40 with PDD and 38 elderly controls by Ewing's battery of autonomic function tests and power spectral analysis of heart rate variability. To determine the prevalence of orthostatic hypotension and autonomic neuropathies by Ewing's classification. RESULTS: There were significant differences in severity of cardiovascular autonomic dysfunction between the four types of dementia. PDD and DLB had considerable dysfunction. VAD showed limited evidence of autonomic dysfunction and in AD, apart from orthostatic hypotension, autonomic functions were relatively unimpaired. PDD showed consistent impairment of both parasympathetic and sympathetic function tests in comparison with controls (all p<0.001) and AD (all p<0.03). DLB showed impairment of parasympathetic function (all p<0.05) and one of the sympathetic tests in comparison with controls (orthostasis; p = 0.02). PDD had significantly more impairment than DLB in some autonomic parameters (Valsalva ratio: p = 0.024; response to isometric exercise: p = 0.002). Patients with VAD showed impairment in two parasympathetic tests (orthostasis: p = 0.02; Valsalva ratio: p = 0.08) and one sympathetic test (orthostasis: p = 0.04). These results were in contrast with AD patients who only showed impairment in one sympathetic response (orthostasis: p = 0.004). The prevalence of orthostatic hypotension and autonomic neuropathies was higher in all dementias than in controls (all p<0.05). CONCLUSION: Autonomic dysfunction occurs in all common dementias but is especially prominent in PDD with important treatment implications.

Aged↗
PubMed2005

En-bloc resection, extracorporeal irradiation, and re-implantation in limb salvage for bony malignancies.

We treated 50 patients with bony malignancy by en-bloc resection, extracorporeal irradiation with 50 Gy and re-implantation of the bone segment. The mean survivor follow-up was 38 months (12 to 92) when 42 patients were alive and without disease. There were four recurrences. The functional results were good according to the Mankin score (17 excellent, 13 good, nine fair, three failures), the Musculoskeletal Tumour Society score (mean 77) and the Toronto Extremity Salvage score (mean 81). There was solid union, but bone resorption was seen in some cases. The dose of radiation was lethal to all cells and produced a dead autograft of perfect fit. Extracorporeal irradiation is a useful technique for limb salvage when there is reasonable residual bone stock. It allows effective re-attachment of tendons and produces a lasting biological reconstruction. There should be no risk of local recurrence or of radiotherapy-induced malignancy in the replanted bone.

Adolescent↗
PubMed2003

Ilizarov wire tensioning and holding methods: a biomechanical study.

AIM: To investigate and compare two specific methods of Ilizarov wire tensioning and hold. METHOD: This study utilised the vertical Hounsfield test machine H25KS, a stress/strain device with a load-cell linked to a computer program. Firstly, the department's present mechanical tensioners were assessed. Secondly, the method of twisting the three designs of wire holding bolts to achieve wire tension, as described by Ilizarov, was assessed. These bolts are described as "cannulated", "slotted" and "Russian" (which are hexagonal headed with a slot down one side). RESULTS: The mechanical tensioners were found to be accurate, if inefficient, with a maximum producible tension of 1330N. The most effective bolts for creation of tension were the Russian, which produced mean wire tensions of 785N at 45 degrees; 1200N at 90 degrees; 1695N at 135 degrees. The cannulated and slotted bolts regularly broke the wires at 90 degrees twist. CONCLUSION: The findings demonstrated two effective methods. The present tensioners were found to be inefficient when compared to the simple twisting of the wire holding bolts, which created equivalent tensions with ease and are capable of producing greater wire tensions. The Russian bolts are recommended for use when wire tension is created by bolt twisting.

Biomechanical Phenomena↗
PubMed2003

Rock-paper-scissors.

A study of 20 doctors in their first or second postgraduate year highlighted deficiencies in their knowledge of the nerve supply of the hand and forearm. The children's game rock-paper-scissors (Figs. 1-3) can be used as a simple aide-memoir for the nerve supply to the hand and forearm. The median nerve creates the "rock position" of the pronated fist (Fig. 1). The radial nerve extends the wrist and hand forming the "paper position" (Fig. 2a and b) and the ulnar nerve creates the "scissor position" (Fig. 3), by clawing the ring and little fingers and spreading the index and middle and adducting the thumb and flexing the interphalangeal joint.

Clinical Competence↗
PubMed2003

The biomechanics of wire fixation in the Ilizarov system.

The purpose of this study was to establish the optimal fixation of tensioned wires to the frame construct in the Ilizarov system. The usual torque to which the fixation bolts were tightened in clinical practice was established by serial testing of orthopaedic surgeons' work in our unit. The force required to produce wire slippage from the different types of wire fixation bolts, tightened to a predetermined torque, was measured using a testing rig. Analysis of the usual torque to which bolts were tightened in clinical practice, revealed values in the range of 5-10Nm. The load required to cause failure of the tensioned wire varied considerably depending on the bolt configuration used and the applied torque. In clinical practice, wires are tensioned using a dynamometer to a variety of loads, depending on the clinical situation, up to 1275N. In applying multiple wires across a single ring, as is normal practice, these loads may be increased still further. The total load transmitted by single wires in weightbearing may be up to 2000N. Utilising the results of our work has enabled us to choose, where practically possible, the optimal bolt configuration for wire fixation. In addition, this work has revealed that in order to withstand the loads seen in clinical practice, wire fixation bolts should be tightened to at least 10Nm. Post-operatively, we now tighten all our wire fixation bolts to 10Nm, using a calibrated torque wrench.

Biomechanical Phenomena↗
PubMed1996

Community-based case management for chronically ill older adults.

A comparison study was done between case managed and non-case managed chronically ill older adults. A decrease in emergency department visits, hospital admissions, hospital length of stay and primary care physician visits resulted. In addition, a +93,519.97 difference in lost net reimbursement was found between the two groups.

Adult↗
PubMed1991

Studying the human-environment phenomenon using the science of complexity.

The principal argument of the present article is that a new theoretical paradigm capable of facilitating the understanding of complex phenomena is necessary to study nursing's claim to its science as the science of unitary human beings, or the integrality between humans and the environment. A research study of the complex human-environment phenomenon illuminating a four-phase methodology is presented. It is argued that much can be learned by the use of the science of complexity to integrate data gleaned from different approaches to knowledge generation into a comprehensive understanding of the human being in the environment as a unified whole.

Adaptation, Psychological↗
PubMed1985

Repatterning of stroke rehabilitation clients following return to life in the community.

The purpose of this study was to learn more about problems stroke patients experience after rehabilitation and how they perceive and interact with their environment. Findings indicate that nurses need to consider individual life patterns, current goals and the resources and impediments of the home and community environment in planning interventions. Subjects wanted a challenging but not overly stressful environment. Most of their energy was consumed with accomplishing the activities of daily living. Complex planning and timing were necessary to continue a few pleasurable activities. Advocates are needed for better design and accessibility in the environment of our aging population, with increasing numbers of chronically ill and disabled, and for all people.

Activities of Daily Living↗
PubMedDate not supplied

Calculation of erythema dose-response curves using a spreadsheet.

A method of using an Excel spreadsheet is described which allows dose and erythema index values to be entered, a sigmoid curve fitted to the data, and a report generated. Summary statistics may be derived from the fitted curve. Data and statistics may be saved in a simple database. It is suitable for implementation by people who have no previous programming experience, although basic familiarity with spreadsheets is assumed.

Dose-Response Relationship, Radiation↗