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Biomedical subjects

B R Davis

Publications and source records attributed to B R Davis.

170 records · Page 10Linked to original sources
PubMedDate not supplied

The contribution of the ossific nucleus to the structural stiffness of the capital femoral epiphysis: a porcine model for DDH.

The preosseous femoral head is thought to be vulnerable to compressive ischemic injury during the treatment of developmental dysplasia of the hip. The ossific nucleus has been proposed to increase the mechanical strength of the capital femoral epiphysis (CFE) and to decrease the risk of avascular necrosis. Sixty mixed-breed fetal and postgestational femoral head specimens were evaluated for structural stiffness in relation to the size of the ossific nucleus within the CFE. The structural stiffness of the CFE in the porcine model was found to increase exponentially with the size of the ossific nucleus. A finite-element model revealed that the presence of an ossific nucleus occupying 40% of the epiphyseal volume reduced the compressive strain in the region of the posterior-superior branch of the medial circumflex artery by an average of 54%. The results of this study support the hypothesis that the presence of the ossific nucleus may protect the CFE from compressive ischemic injury in the treatment of DDH.

Animals↗
PubMedDate not supplied

The prognostic value of the duration of the ambulatory electrocardiogram after myocardial infarction.

The purpose of this study was to examine the value of various durations of ambulatory ECG recording with regard to providing useful prognostic information. The authors explored a decision theoretic approach to determine the most useful period of monitoring for making a treatment decision based upon postulated benefit-to-risk ratios of antiarrhythmic therapies. They used data collected as part of the Beta-Blocker Heart Attack Trial (BHAT), a randomized clinical trial of propranolol versus placebo in 3,837 post-myocardial-infarction patients. In BHAT, 1,336 placebo-treated patients had a 24-hour ambulatory ECG that had at least 23 readable hours. Sensitivity and specificity were calculated for eight definitions of ventricular arrhythmia using either total mortality or sudden death (death within one hour of symptoms) as an endpoint. These indices were obtained using the first 1, 2, 4, 6, 12, and 24 hours plus a random hour, a random daytime hour, and a random nighttime hour of the 24-hour ECG of 1,336 placebo-treated patients. The study showed that in the case of high-risk, low-benefit therapies, no test is needed to make a treatment decision. No one should be treated. In the case of high-benefit, low-risk therapies, again, no test is required. Everyone should be treated. For therapies in the middle benefit-to-risk ratio range the most appropriate test for a treatment decision changes from the very specific to the most sensitive. Twenty-four hours of ambulatory monitoring is usually not necessary for a treatment decision, since four hours is likely to be sufficient.

Adult↗
PubMedDate not supplied

Statistical methods that distinguish between attributes of assessment: prolongation of life versus quality of life.

The authors propose a method to generate information relevant to the decision tree that adds additional perspective to the characterization of health quality during survival. Their approach uses survival data to distinguish two attributes of utility: prolongation of life and quality of life (QOL). Health-state transition probabilities correspond to the prolongation of life and are modeled in a discrete-time transient semi-Markov process. Quality-of-life-state transition probabilities are derived from the assumptions of a simple recurrent Markov process. They reflect events within the health-state sojourn time that differentiate perceptions of pain and suffering over a short fixed time period. Outcomes for these two dimensions of utility are highly relevant to the assessment of medical technology that might prolong life at the cost of increased pain and suffering, implying a reduced QOL. The methods are demonstrated on a subset of follow-up data from the Beta-Blocker Heart Attack Trial (BHAT).

Adult↗
PubMedDate not supplied

Experimental approaches to determining the choice of first-step therapy for patients with hypertension. The ALLHAT Research Group Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial.

Detection, treatment and control of hypertension is one of the best proven approaches to prevention of cardiovascular disease. Antihypertensive treatment trials have convincingly demonstrated that diuretics and beta-blockers reduce the risk of stroke and coronary heart disease. Corresponding information is not yet available for newer classes of antihypertensive drug therapy such as calcium channel blockers, angiotensin converting enzyme inhibitors and alpha 1 receptor blockers. Several experimental studies are now addressing this question. The largest such trial (n = 40,000) is the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). This manuscript describes two studies (TOMHS and the VA study on antihypertensive agents) that compared several classes of antihypertensive drugs with regard to blood pressure outcomes and ALLHAT, which is comparing the effect of four first-step approaches to antihypertensive therapy on combined incidence of fatal coronary heart disease and non-fatal myocardial infarction.

Aged↗
PubMedDate not supplied

An experimental model for the study of thermochemotherapy in vivo.

Human melanomas serially passaged in nude mice as xenotransplants were used as models for the study of the effects of thermochemotherapy of human malignant tumours in vivo. Three such melanomas, one (BRO) fast-growing, one (SCH) slow-growing, and one (BEL) of intermediate growth rate, were chosen. One group was left untreated as a control, one received chemotherapy (cyclophosphamide), one received hyperthermia, and one a combination of both treatments. In all three tumours, the best results were obtained associating chemotherapy with hyperthermia. The fastest growing tumor responded more than the slower, which responded better than the slowest. This model should prove useful in testing the effectiveness of anticancer agents used in association with hyperthermia.

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