Ernst O. Attinger

Wall Properties of Veins

After a brief review of the venous wall structure, the physical properties of veins are discussed in terms of their stress-strain relationships. In contrast to the high pressure arterial system, the low pressure venous system may exhibit large changes in volume without major pressure changes. Inferences about wall properties and intravascular volume from pressure measurements alone are thus meaningless. Depending upon the interplay between intra- and extravascular forces, the venous cross section may oscillate between complete collapse and a circular shape. The stress-strain relationships are both nonlinear and time dependent. Comparative data are given for representative arteries and veins and the distribution of blood volume within the peripheral vasculature is discussed. Finally, some of the venomotor agents and their effects upon stress-strain relations are reviewed.

Identification of the high-risk population for serious burn injuries

Abstract The incidence of serious burn injuries has been determined for the Commonwealth of Virginia during a 21-month period. The data set included all patients with burn injuries who entered the hospital and were considered serious enough to require inpatient treatment. The risk for burn injury was calculated by age, race and sex. Examination of the data identified a high-risk population that was prone to serious burn injuries. The demographic characteristics of the burn population has been correlated with their socio-economic status.

Epidemiology of minor burn injuries

The incidence of minor burn injuries has been determined for the Commonwealth of Virginia during a 17-month period. The data set included all patients with burn injuries receiving treatment in the emergency department that did not require hospitalization. The risk of burn injury was calculated by age, race and sex. Examination of the data revealed large differences in the magnitude of age-specific incidence rates between men and women and the white and non-white population. Differences in the economic status of the population may explain a large proportion of the variation in the crude burn rates.

Interactions between carotid sinus mechanoreceptor and chemoreceptor reflex loops

SummaryOur experiments were designed to evaluate the combined influence of the mechanoreceptor and chemoreceptor control loops on the cardiovascular and respiratory systems. Both carotid sinus areas were isolated by a complete blind sac preparation in chloralose anesthetized dogs in which a flow probe had been implanted previously on the ascending aorta. The following variables were continuously monitored: central aortic pressure, heart rate, cardiac output, vascular resistance of a hind limb, tidal volume, respiratory rate, and oxygen consumption. While one sinus was submitted to step changes of pressure, the opposite sinus was kept at constant mean pressure. In addition, one sinus was perfused with either oxygenated of deoxygenated blood at constant flow rate.These studies show a definite interaction between the control loops initiated by the carotid sinus mechanoreceptors and those initiated by the chemoreceptors. The influence of the chemoreceptors is most marked in the peripheral beds, where it shifts the whole response curve of the mechanoreceptor control loop upward. This response accounts for most of the upward shift of the pressure response curve.On the other hand, the mechanoreceptor loop affects the ventilation, but this effect is range dependent, being most marked for the low pressure perfusion of the carotid sinus.

Hierarchy levels in the control of blood flow to the hind limb of the dog

In order to quantitatively assess the dynamic interactions between different levels of the O2 transport system control hierarchy from the dynamics of the relative contribution by individual cardiovascular and respiratory variables to the response of the system to stress, flow perturbations were introduced in the hind leg of greyhounds by:1) passive motion of the biceps muscle, 2) electrical stimulation (el. stim.) of the muscle nerve, 3) el. stim. of the femoral and sciatic nerve, 4) el. stim. of the proximal end of both nerves, 5) el. stim. of the peripheral end of both nerves, 6) peripheral stimulation after autonomic blockers and 7) peripheral stimulation after Flaxedil. The following variables were continuously measured: upper and lower inflow in the biceps, inflows into the stimulated and the contralateral leg, O2 saturation of the venous outflow from the muscle and the leg, arterial pressure, heart rate, respiratory rate and tidal volume; and their responses to perturbations were characterized by four parameters [delay time, initial slope, maximum (or minimum) and average response]. Of these, the slope was found to be the most sensitive index of stimulus specificity, while the traditionally measured steady state response, although an important consideration for performance adaptation to stress, does not permit a differentiation between the various control mechanisms which mediate the response. These results indicate that the low frequency dynamics of cardiovascular and respiratory performance contain essential information about the type of control arrangement existing at a given moment. Marked differences in both time course and magnitude of flow responses in vascular beds arranged in parallel and in series were observed with corresponding differences in the changes of the O2 content of their respective venous outflows. From the ranking of the four parameters a numerical estimate of the overall response as well as of its peripheral and central components was obtained. Between the different experimental conditions the spectrum of the overall responses ranged from predominance of centrally mediated control mechanisms (as judged by the magnitude of the contribution by “central” indicators) to predominance of locally mediated control mechanism. The latter depended on the presence of increased metabolic activity. If hierarchy levels are defined functionally (rather than structurally) on the basis of the magnitude of the response of the different indicators our results show a complete reversal of the hierarchical ordering between stimulation of the proximal and peripheral end of the sciatic and femoral nerve. An appropriate choice of sufficient and adequate parameters for the characterization of integrated response pattern is a crucial prerequisite for this type of analysis.

Impacts of the Technological Revolution on Health Care

The last three decades have seen extraordinary advances in biomedical research and in patient care. The prevalence in disease pattern has changed from infectious to chronic diseases; and many of the conservative treatments of the past have given way to aggressive and often heroic procedures in the operating room, in a multitude of intensive care units, and in specialized treatment centers. At the same time, health care expenditures have risen from 13 billion or 4.5 percent of the gross national product (GNP) in 1950, to 322 billion or 10.5 percent of the GNP in 1982. Since the burden of these expenditures has increasingly shifted from individual patients and philanthropic sources to society as a whole, both government and the private sector have become actively involved in attempts to stop or at least slow down the rapid escalation of health care costs. In this paper, I am going to discuss the role which biomedical technology has played in this transition of the health care system.

Evaluation of an emergency medical service referral system for burn patients

It is the purpose of this report to examine the process of burn care of hospitalized burn patients in the Commonwealth of Virginia over a 21 month period. Eighty-nine per cent of the hospitals within the state participated in the study, the results of which provide a positive indication of the performance of our statewide emergency medical service referral system. This system was successful in redistributing patients, with the more severely burned patients being treated in the specialty burn treatment facilities. The process of burn care within the hospital setting was also consistent with the patients severity of injury.

Age distribution, education and societal structure

Abstract Age distribution, educational distribution and societal structure are interrelated parameters that, in the past, were adjusted to each other in an equilibrium that was only perturbed by rather small and slow changes. Built-in trial and error control mechanisms were evidently capable of containing these minor perturbations without excessive instabilities. Recently, major and fast changes have been occurring in the age distribution through the substantial extension of human life expectancy, and in the educational distribution through the wide availability of educational opportunities. The existing trial and error control mechanisms seem to be inadequate for such major perturbations, and new controls will have to be introduced in order to avoid serious instability and disruption. While the age distribution cannot be controlled through morally acceptable means, ways must be found to control the educational distribution, and to match it to existing societal needs.