The role that the pattern of vessel wall growth plays in determining pressure-lumen area (P-A) and pressure-compliance curves was examined. A P-A vessel model was developed that encompasses the complete range of pressure, including negative values, and accounts for size given the fixed length, nonlinear elastic wall properties, constant wall area, and collapse. Data were obtained from excised canine carotid and femoral arteries, jugular veins, and elastic tubing. The mean error of estimate was 8 mmHg for all vessels studied and 2 mmHg for blood vessels. The P-A model was employed to examine two patterns of arterial wall thickening, outward growth and remodeling (constant wall area), under the assumption of constant wall properties. The model predicted that only outward wall growth resets compliance such that it increases at a given arterial pressure, explaining previously contradictory data. In addition, it was found that outward wall growth increases the lumen area between normal and high pressures. Remodeling resulted in lumen narrowing and a decrease in compliance for positive pressures.

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A real-time (instantaneous) system is presented to measure the dynamic volume of the left ventricle. This system uses the invasive measurement of long axis diameter, short axis diameter, and wall thickness of the cardiac left ventricle. Three pairs of pulse-transit ultrasonic dimension transducers are used to obtain these measurements. The dynamic volume was then found by applying these measurements to an ellipsoidal shell model of the left ventricle. It is possible to obtain on-site, real-time, continuous measurements of the left ventricular volume (LVV) by employing an electronic device which implements a corrected volume equation for the ellipsoidal shell model. The device's output is a calibrated estimation for the LVV. The function of the device is shown to compare well with other accepted measurements for the LVV.

An instrument is presented which produces a simulated circulatory pulsatile pressure wave for small sized vessels. The linear hydraulic pressure-pulse actuator (LHPA) is designed to be extremely versatile, that is, a blood pressure wave source of any shape, amplitude, offset and frequency can be simulated. In addition, the LHPA can reproduce accurately a real pulse pressure wave by simply imputting an actual data record of a circulatory pressure pulse. The design is accomplished by incorporating the use of a linear force solenoid driven with a voltage-to-current source power amplifier. Testing of the device is presented here, as well as pressure pulse results from a recorded pulsatile pressure input to the LHPA. The device is simple to implement in that its response is linear, for volume changes upto +/- 5 mL, without the need for feedback compensation.