We have demonstrated the feasibility of using laser doppler spectroscopy to map regional blood flow distribution on the surface of the cerebral cortex. Rhesus monkeys underwent craniotomy, with replacement of part of the calvarium by a transparent plastic dome. A stroke was produced on one side by ligation of the middle cerebral artery. A flow index was computed from a weighted bandwidth of the doppler spectrum of helium-neon laser light scattered from the surface of the cortex, the doppler shift being due to scattering from moving blood cells in the microcirculation. By measuring the doppler flow index at a grid of points over the surface, the region of the stroke was easily delineated, and its progression with time observed. The method provides a rapid measurement with a spatial resolution of about 1 mm.
A method is given for the in vitro evaluation of transfusion therapy of patients with sickle cell anemia. Changes in volumetric flow rate, hemoglobin flow rate, and oxygen delivery at three values of PO2 (25, 40, and 80 mmHg) induced by transfusion of two units of AA blood in three patients are evaluated. The viscosity-shear rate data are obtained in a precision cone and plate viscometer with controlled environment. This data is then used to calculate flow rates in model tubes of varying diameters (50-500 microns). The increase in oxygenated hemoglobin flow rates at low oxygen tensions after transfusion can be striking-sometimes greater than a factor of two. A preliminary evaluation of the potential effect of auto-transfusion or androgen therapy on these flow rates is also discussed.
The Biomedical Engineering Division of the Indian Institute of Technology in Madras engages in a program of research, development and teaching. A visitor to our institution would, at any time, find a considerable variety of projects and courses being followed as well as active consultation with industry and the medical profession.
Flow through the vocal cords and collapsible tubes passes through a narrow elastic gap whose cross-sectional area varies with the transmural forces induced by the flow. In both systems, the equations used to describe steady flow are the same and have similar dependence on cross-sectional area. Since collapsible tubes have been shown to be flow-controlled nonlinear resistances (QNLR) analogous to transistors, it is expected that the vocal cords will also exhibit the QNLR property for steady flow. A new equivalent circuit including a transverse impedance to represent wall motion is postulated for the vocal cords based on the tube analogy. Collapsible tubes oscillate when the magnitude of their negative dynamic resistance is greater than the ac resistance of the external circuit plus parasitic tube impedances. Self-oscillation conditions for the cords should be the same. since they are common to all negative resistance systems of QNLR type.
A low-cost FM/FM radio telemetry system is detailed, designed for motion analysis of the knee joint during walking in total knee replacement patients.
Present techniques of assessing rotational alignment in bone are limited to gross anatomical and radiographic observations made at a single point in time. Because of these quantitative limitations, this paper describes a radiographic technique devised to give precise information elucidating the direction, magnitude and site of rotational change. This technique is based on the radiographic monitoring of a positional change, in vivo, of biologically inert marker pins in the long bones. Animal investigations have demonstrated the validity of the in vivo angular assessments and have also shown morphologic and biomechanical compatibility. Laboratory experiments simulating an in vivo deflection were performed with a correlation of 0.999 found between the calculated angles and those measured in vitro.
It can be seen that the radiation emissions of nuclear power plants are small indeed, compared to natural background radiation and other man-made sources of radiation. For example, the poulation is exposed to 100 times more radiation from television sets than from nuclear power reactors. The assumed risks to the people in this country from nuclear power reactors are also small compared to the normal risks which are tolerated in this society. The complete elimination of all hazards is a most difficult if not impossible task. If we need and desire a certain level of electrical energy, if we must choose between alternative sourves of the energy, then it is apparent that the total impact on our health from nuclear power generation of electricity, under normal operations and in consideration of catastrophic accident probabilities, is significantly less than that of continuing or increasing use of fossil fuels to generate electricity.
This report describes a model that may be used in the evaluation of the mechanism(s) of action engaged in renal autoregulation of blood flow. This model was derived from both the steady-state and transient behavior of the renal autoregulatory response. The response computed by an analog computer simulation of the model compared favorably to those observed in experimental animals.
The ambulance service is an important component in the emergency medical system of a community. The availability of performance information on several aspects of the ambulance system may improve ambulance management. The location of new ambulance stations, selection of the destination hospital for urgent cases, scheduling of crew changes, and evaluation of crew performance can be approached through an examination of existing data. Management use of such an information system by the Victorian Civil Ambulance Service in Melbourne, Australia is included in the discussion.
