AN EXPERIMENTAL AND THEORETICAL INVESTIGATION OF THE OSCILLOMETRIC METHOD OF INDIRECT BLOOD PRESSURE MEASUREMENT
Abstract
In recent clinical studies utilizing the oscillometric method of indirect blood pressure measurement, the cuff pressure at which cuff pressure oscillations are maximum in amplitude has been found to closely correspond to true mean arterial pressure. Although a reasonable correspondence between the cuff pressure at maximal oscillation amplitude and true mean arterial blood pressure appears to occur clinically, the physics of the oscillometric method is poorly understood. The present research critically examines the physics involved in the oscillometric method using both experimental and theoretical studies. Employing several simplifying assumptions, the complex system of blood pressure cuff, arm tissues and artery is reduced to a simplified experimental model consisting of a collapsible elastic vessel enclosed within a rigid compression chamber filled with liquid and air. A one-dimensional theoretical model based upon the experimental model is also derived. Employing the experimental and theoretical models, the effects of system parameters are examined. The accuracy of the oscillometric method in predicting direct mean arterial pressure for the model was found to be most dependent upon the ratio of compression chamber air volume to unstressed arterial volume, with a decrease in accuracy as the volume ratio increases. The existance of an optimal value for the ratio of compression chamber air volume to unstressed arterial volume is both suggested experimentally, and shown to exist theoretically. Increasing arterial length was found to have a minimal effect for small volume ratios, and result in a slight improvement in accuracy for large volume ratios. The effects of arterial distensibility on the oscillometric method were examined using the theoretical model and shown to have a minimal effect on the prediction of mean arterial pressure. The present results from the simplified model indicate several aspects of the clinical method of oscillometric blood pressure detection which should be examined. Detailed recommendations are made.
Degree
Ph.D.
Subject Area
Biomedical research
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