Search PubMed⌕ Search

Biomedical subjects

T Findley

Publications and source records attributed to T Findley.

17 recordsLinked to original sources
PubMed1999

Adaptation of passive rat left ventricle in diastolic dysfunction.

This article deals with providing a theoretical explanation for quantitative changes in the geometry, the opening angle and the deformation parameters of the rat ventricular wall during adaptation of the passive left ventricle in diastolic dysfunction. A large deformation theory is applied to analyse transmural stress and strain distribution in the left ventricular wall considering it to be made of homogeneous, incompressible, transversely isotropic, non-linear elastic material. The basic assumptions made for computing stress distributions are that the average circumferential stress and strain for the adaptive ventricle is equal to the average circumferential stress and strain in the normotensive ventricle, respectively. All the relevant parameters, such as opening angle, twist per unit length, axial extension, internal and external radii and others, in the stress-free, unloaded and loaded states of normotensive, hypertensive and adaptive left ventricle are determined. The circumferential stress and strain distribution through the ventricular wall are also computed. Our analysis predicts that during adaptation, wall thickness and wall mass of the ventricle increase. These results are consistent with experimental findings and are the indications of initiation of congestive heart failure.

Adaptation, Physiological↗
PubMed1998

Evaluation of residual stress in rabbit skin and the relevant material constants.

Material constants are needed in order to evaluate stresses. The material constants for orthotropic rabbit skin when residual stresses are eliminated, have been evaluated by Tong & Fung [(1976). J. Biomechanics 9, 649-657]. It is well documented that a circular skin sample taken from the human body becomes elliptical in shape. Thus, it is clear that there are residual stresses in human skin which need to be taken into consideration when evaluating the material constants. In this paper, we therefore evaluate the material constants for rabbit skin taking into account residual stresses.

Animals↗
PubMed1998

Optimal patterns for suturing wounds.

A mathematical model for computing stresses in sutured human skin wounds is presented. The model uses the incremental law of elasticity and elastic constants valid for in vivo orthotropic skin. The model is applied to compute the principal stress and displacements resulting from suturing small elliptical and circular wounds in a large flat sheet of skin, in order to determine the optimal suturing patterns. It is observed that the average stress index for a circular wound sutured toward the center is almost double that of a wound sutured transverse to the diameter. Thus, the latter type of suturing pattern is preferable. Similarly, suturing an elliptical wound transversely produces a lower average stress index than a circular wound of the same area. It is also found that the optimal ratio of semi-major to semi-minor axis of an elliptical wound is near 3 (for abdominal wounds), i.e., this ratio produces the most uniform stresses along the wound edges, where wound healing is slowest. Since high stresses have adverse effects on healing and blood flow, this work, depicting regions of high stresses, may be used along with other biological factors to help predict regions of slower healing in sutured wounds.

Algorithms↗
PubMed1997

Residual stresses in oscillating thoracic arteries reduce circumferential stresses and stress gradients.

The purpose of this paper is to examine the effects of residual stresses and strains in the oscillating arteries on the stress distribution in the vascular wall. We employ a static theory of large elastic deformations for orthotropic material (Chuong and Fung, 1986, J. biomech. Engng 108, 189-192) with the acceleration term added to make the theory dynamic. We use the static elastic parameters of residual stresses in our analysis because the dynamic parameters are not available in the literature. Our analysis reveals that the effect of considering the residual stresses is to decrease the very large circumferential stresses at the inner wall by 62% and reduces the stress gradient through the arterial wall by 94% compared to the case when residual stresses are ignored. Thus, because the arteries do contain residual stresses, the consequent lower stresses at the inner wall and the reduced stress gradient may reduce the progression of atheroma. Our computations show that the stress gradients do not depend on the heart rate.

Animals↗
PubMed1995

Influence of respiration on metabolic, hemodynamic, psychometric, and R-R interval power spectral parameters.

Because respiration modulates autonomic activity, we determined the magnitude of perturbation of changing breathing frequency and tidal volume on metabolic, hemodynamic, psychometric, and R-R interval power spectral parameters. Seated subjects breathed at three different rates and five different volumes with each of the different rates. Breathing rates and volumes were percentages of the subject's resting breathing pattern and, therefore, identical across all subjects. Increases in rate and volume resulted in significant perturbations in end-tidal CO2 production, CO2 production, ventilatory equivalent for O2, comfort levels, and R-R interval power spectra (P < 0.05). The magnitude of the perturbations in the above parameters indicated a substantial upset in all subjects' metabolic, hemodynamic, and comfort homeostasis, precipitating a significant loss of vagal tone. The implications of our findings are that imposed breathing patterns used to modulate autonomic outflow should be tailored to the individual's resting breathing pattern. These data further support the urgent need for concomitant metabolic and respiratory measurements when analyzing and interpreting heart rate variability data.

Adult↗
PubMedDate not supplied

Factors influencing the specialty choice of the physical medicine and rehabilitation graduating class of 1994 and the entering class of 1995.

To understand better how career choices are made by physiatrists, a 16-item, 7-page questionnaire was sent to all 1994 graduating physical medicine and rehabilitation (PM&R) resident physicians in the United States. Of the 343 senior residents, 202 completed the questionnaire for a response rate of 59%. The questionnaire focused on the following areas: timing of the decision to enter PM&R; and how the medical school curriculum, certain groups of people, and certain specific factors influenced their choices. There were 130 factors modeled after the American Association of Medical Colleges (AAMC) annual medical student questionnaire that the recipients were asked to grade on a numerical scale: 1 = unimportant to 5 = very important. Of the graduating residents, 60.1% (119/198) made the decision to enter PM&R in their 3rd or 4th yr of medical school, 13.1% (26/198) in the first 2 yr, and 11.1% (22/198) after starting another residency. The five factors ranked most important in the decision were (mean rank score): sufficient time/flexibility for family obligations (4.60); opportunity to make a difference in peoples lives (4.57); interest in helping people (4.55); types of patient problems encountered (4.50); and consistency with personality (4.49). We also obtained the AAMC's 1993 annual data on medical students choosing PM&R. Their top five factors were the same as those listed by the graduating residents, but in a slightly different rank order. Profiles have also been derived on those graduating PM&R residents who chose an academic career (n = 68) v nonacademic (n = 133) and fellowship (n = 34) v nonfellowship (n = 163).

Career Choice↗
PubMedDate not supplied

Functional outcome and comorbidity indexes in the rehabilitation of the traumatic versus the vascular unilateral lower limb amputee.

This study compared the Functional Independence Measure (FIM) scores of traumatic (n=12) and vascular (n=12) unilateral lower limb amputees at admission and discharge from a rehabilitation facility. FIM scores that were measured were amputation FIM subscores and total FIM scores. Comorbidity indexes were developed to weight the stump condition and comorbidities seen in both groups. The vascular group was significantly (P<0.01) greater stump comorbidity, but there was no significant difference with respect to length of stay, medical comorbidity score, and amputation and total FIM scores both at admission and discharge between the two groups. Medical comorbidity was significantly (P<0.05) correlated with amputation and total FIM scores at discharge for traumatic amputees with r = -0.64 and r = -0.66, respectively. Stump comorbidity was significantly (P<0.05) correlated with total FIM at discharge with r = -0.64 for vascular amputees. Medical comorbidity was a good predictor of discharge FIM scores for traumatic amputees, whereas stump comorbidity predicted discharge FIM scores for vascular amputees, although not as well. In conclusion, inpatient traumatic amputees may be younger than vascular amputees, but traumatic amputees may not necessarily be healthier or do better functionally at discharge than vascular amputees.

Adult↗
PubMedDate not supplied

Practice and career satisfaction among physiatrists. A national survey.

To evaluate physiatrist career satisfaction and current practice patterns, a 15-page survey was mailed randomly to 400 fellow members of the American Academy of Physical Medicine and Rehabilitation. The 208 questionnaires (52%) returned revealed respondents' level of satisfaction with career choice, current practice, relationships with other physicians, their own residency training, and problems experienced that impede their practice. Factor analysis identified six areas of satisfaction: time demands, organizational support, current practice, current specialty, profession, and training. Problems with work consisted of four factors: external intrusions into practice, having to deal with non-rehabilitation problems, dealing with PM&R problems, and insufficient time for patients. Results showed that 75% of physiatrists were satisfied with their practice/profession. Satisfaction with current practice was greater with fewer external intrusions into practice, a larger percentage of income from traditional non-managed payment sources (including Medicaid), and less competition. Changes in health care, such as managed care, competition, and increased external regulations, appear to interfere with current practice. Variation in satisfaction was not significantly correlated with size of community, variation in rates of payment denials, workloads of greater than 50 hours per week, and a number of other factors that one might expect to affect satisfaction. Physiatrists had made many changes in their practice in response to the changes in the health care environment but had not cut care for indigent patients. Needs for greater residency training in outpatient clinics, physicians' offices, managed care, and long-term care settings were expressed. This is the first comprehensive published report on physiatric satisfaction in a changing health care environment. Further research in some of the areas will be required.

Adult↗
PubMedDate not supplied

Randomized clinical trials in medical rehabilitation research.

The purpose of this article is to provide researchers and clinicians with a basic understanding of randomized clinical trials and to discuss their potential application to and limitations in the field of physical medicine and rehabilitation. A brief history of the development of randomized clinical trials, definitions of clinical trials, types of trials, and overview of methodological issues related to design are offered. Information is provided about the need to establish clear and concise study objectives and to explicitly define interventions and expected outcomes. Recommendations for developing clinical protocols and determining adequate sample size are presented, and various statistical considerations, including power, are discussed. Issues related to sampling strategies, and recruitment are reviewed. Importance of randomization and blinding is emphasized. Readers are also referred to other resources available on this topic. Finally, the authors describe shortfalls associated with the use of this design in rehabilitation research. These are further explored and discussed in terms of the actual benefits and limitations of randomized clinical trials in physical medicine and rehabilitation research. Recommendations are made regarding the use of this methodology to address relevant needs in clinical practice.

Bias↗