ANALYSIS OF THE VASCULAR UNLOADING TECHNIQUE FOR BLOOD PRESSURE MEASUREMENT BY USE OF A CIRCULATORY SYSTEM MODEL.

A study to relate the accuracy and repeatability of the vascular unloading technique of blood pressure measurement to vascular system parameters is described. Difference-differential equations of fluid flow in distensible tubes were used to obtain pressure-flow-volume relationships for the blood vessels of the human finger. The radii, lengths and numbers of variously sized vessels in the finger were extrapolated from previously obtained data, and a segmented hemodynamic model was constructed. This model accounts for the blood volume changes in the vessels due to variations in vascular compliance and blood pressure. Volume changes due to counter-pressure applied to the finger vasculature were calculated using the model. The model results were verified by comparing them to measured pressure-volume signals in the human finger. The model was shown to agree closely with experimental measurements of pressure, flow, and volume

Influence of vascular parameters on the effectiveness of intra-aortic balloon pumping: A model study

The intra-aortic balloon pump has been widely used as a temporary heart-assist device. In this investigation, a nonlinear mathematical model of the arterial system and intra-aortic balloon pump was studied analytically. Thus, the influences of a number of vascular parameters on the effectiveness of intra-aortic balloon pumping (IABP) were determined. The effects of changes in vascular parameters of the model on a number of performance indexes were investigated. These performance indexes (aortic mean diastolic pressure, aortic end diastolic pressure, cardiac output, coronary flow and phase differences between the fundamental Fourier components of aortic root pressure and flow) were used as the criterion for an evaluation of the effectiveness of the assist pump. The following vascular parameters were perturbed by four steps (±10%, ±20%) from the values in the standard model: heart rate, peripheral resistance, left ventricular pressure, aortic elastance, aortic radius, arterial wall thickness, and aortic length. This model was evaluated for a wide range of balloon-pump phase-control settings (assisted case) and for the unassisted case (when the pump is disabled). It is concluded that changes in heart rate, peripheral resistance and left ventricular pressure cause the most significant changes in pump performance. © 1982 IFMBE

Semitransparent reconstruction of cardiac structures from MR data

A computationally intensive approach to three-dimensional cardiac magnetic resonance (MR) reconstruction is described. This technique used semitransparent surface rendering to give a view of human left and right blood pools within the cardiac structure. Blood was given a colored solid surface, while the cardiac wall was semitransparent

The use of fractal dimension in MR image segmentation: A variance technique

The use of a variance driven dimension determinator to find the left ventrical/blood pool border in cardiac MR (magnetic resonance) images is considered. Use is made of the fact that the determinator produces a low value on borders between two different distributions. The smallest closed contour surrounding the center of the image is then labeled as the border of interest, using the knowledge that the scanner is centered upon the left ventrical. It is concluded that methods of segmenting MR cardiac images using fractal dimension have considerable promise

Hands-On Microprocessor Education at the University of Rhode Island

This paper documents the impact of microprocessor technology on electrical engineering education at the University of Rhode Island. Originally introduced as a method of giving computer experience to a larger number of students, it has become a key element in the undergraduate curriculum. “Microprocessor Laboratory” emphasizes hands-on experience by making computers available for “check-out” use at home. It is introduced as a required course at the sophomore level and the textbooks used are manufacturers’ manuals. We employ a series of nine basic exercises and couple these to an end-of-semester project. The course is offered each semester and attracts students from other engineering disciplines and from other colleges within the University. It has been successfully adapted to a five-week summer session and a four-day short course for engineering faculty. The course forms the basis for introducing microprocessors into other, more advanced engineering courses. Copyright © 1981 by The Institute of Electrical and Electronics Engineers, Inc

Intra aortic balloon computing: Observations from a mathematical model and in vivo experiment

The authors examined the dynamics of an intra aortic balloon (IAB) in the aorta and its effect on the hemodynamic response of the cardiovascular system. A mathematical model was developed and in vivo animal experiments were performed. The model describes the balloon inflation and deflation as an aortic-pressure-dependent wavefront. To validate the model, X-ray images and hemodynamic waveforms were acquired from animal experiments using two differently shaped balloons. The model-generated images and hemodynamic data compare very favorably to those taken in vivo. This phenomenon is shown to greatly affect the hemodynamic effectiveness of the IAB. Furthermore, the wavefront and the effectiveness are directly related to balloon length. Thus, short balloons are significantly more effective than long balloons of the same overall volume

Real-time graphics display and simulation for the intra aortic balloon pump

A system was developed to simulate the operation of an intra-aortic balloon pump (IABP) console, and the corresponding patient response. It displays aortic pressure and left ventricular pressure as sliding waveforms in real-time, as well as all of the IABP controls. The system is designed to execute in a PC architecture. The embedded arterial model is based on a multiple-order nonlinear system model of the vascular system. This allows health care professionals to practise controlling an IABP without using a commercial pumping console. Thus, the software is a very useful educational platform

Intraaortic balloon pump: optimization assist device parameters during low cardiac output by use of a mathematical model

It has been suggested that volume displaced by the intraaortic balloon is more significant than any other IAB (intraaortic balloon) factors (such as timing and speed), especially during the low cardiac output states. To investigate the operation of the balloon in the aorta during such conditions, a refined mathematical model of the balloon system was incorporated into a cardiovascular model. The model describes the balloon inflations as a pressure-dependent wavefront. This results in cardiac ouptut that is not linearly proportional to IAB volume. Thus for example under typical condition a single-chamber 4-cm3 IAB has the same effect on cardiac output as a 60-cm3 IAB

Fractal dimension as a method of segmenting cardiac images

Cardiac magnetic resonance (MR) images were segmented by the use of fractal concepts. The method utilized is a robust two-dimensional extension of the previous work of T. Lundahl et al. (IEEE Trans. on Medical Imaging, vol. MI-5, no. 3, 1986). The results show that this technique can provide a method to extract cardiac borders from MR images in situations where conventional approaches fail

Intraaortic balloon pumping during low cardiac output: Validation of a mathematical model

Conventional intra-aortic balloon therapy has been of less than optimal value when used to improve cardiac output in cases of extreme heart failure. In order to determine the major factors responsible for this situation, a mathematical model was constructed. In the model it is possible to place an arbitrary size balloon within any section of aorta. The model was validated by comparing predicted cardiac output to that measured in a series of eight animal experiments. The animals were placed in a halothane-induced low-output state. Intra-aortic balloons of from 20 to 75 cc were used. With 138 observations from both model and experiment, the correlation was good (r = 0.99, p \u3c 0.00001). Thus the model was considered valid for detailed investigation. Increasing the balloon displacement in the model from 40 to 100 cc can increase cardiac output from less than 10% to more than 40%. Thus this may be a way to improve device efficacy