A Study Into Design and Development of Noninvasive Blood Pressure Monitoring Device

Abstract

This work describes the design, development and testing of an instrument for continuous, noninvasive measurement of blood pressure in humans. While there is a great need in medical fields for such an instrument, it is not available at present. Tonometry principle is used in this work. This method has the difficulty in locating the tonometer over the artery. However, this difficulty was overcome by locating the tonometer where major arteries are absent, such as fingertips or ear lobes. Linear relationship between the blood pressure variations in the arterioles, capillaries and the main arteries, is shown by mathematical analysis and simulation tests. While it is shown that it is possible to obtain the measurements in various locations, the present work concentrates to develop a device suitable for the finger. Such device is built and tested successfully on a number of individuals as well as in a hospital. Also , a calibration procedure using a standard cuff method has been worked for this device. However, one difficulty has been still remains to be solved, namely, long-term zero shift of the measuring system. This is due t o the convection currents and the deterioration of the adhesive presently in use .