Miniaturized Pressure Transducer Intended for Intravascular Use

A pressure transducer utilizing an electrooptical method is described. As the transducer is primarily intended for intravascular use, it has been given the form of a catheter with the pressure-sensing part at the one end and the necessary bulky components at the other end. A light guide of glass fibers inside the catheter transports light from a light source to the measuring tip. Here the pressure variations affect a movable membrane which reflects a variable amount of light into another light guide leading to a photodetector. The variations in the signal from the detector are thus proportional to the applied pressure. The main part of the paper is concerned with a theoretical investigation of the principle for transducers of this type. This analysis gives relationships between the geometry of the measuring tip, the number of glass fibers, and their distribution, material constants, and signal parameters. Using these relations, it is possible to arrive at the fundamental limitations of the method, particularly in regard to the miniaturization. Furthermore, some temperature effects which are generally neglected, are analyzed.