Using Experimental Modal Analysis Principles to Evaluate the Dynamics of Catheter Transducer System in Invasive-Pressure Measurements

The main objective of this paper is to employ basic modal testing principles in order to assess the dynamic behavior of fluid filled catheter in invasive pressure measurements. This type of dynamic measurement is particularly suitable in biomedical engineering applications, where accurate blood pressure readings are required in order to assess the patient real condition. The measurement procedure requires that a fluid filled catheter be introduced in the patient’s body through a prescribed artery, and its tip positioned in the desired location where the blood pressure is to be monitored. The other catheter end is connected to a pressure transducer that senses the pressure pulse transmitted through the fluid along the catheter length. This blood pressure pulse can then be monitored by appropriate clinical hardware. Previous studies reported that the catheter-transducer system alters significantly the shape and amplitude of the pressure pulse transmitted along the catheter’s length. In particular, the catheter’s radial compliance and geometry appears to be an important factor in the pressure distortions observed. In the present work experimental simulations are performed by using a catheter-transducer system that is connected to an artificial blood pressure simulator. This simulator is capable of generating pressure pulses that are close to real signals observed in patients during blood pressure monitoring. A special type of piezoresistive pressure transducer is used in the experimental work in order to measure the simulated pressure signals. One transducer is used tq capture the input pressure to catheter at the simulator stopcock. A second pressure transducer is used to measure the pressure at the other catheter’s end. Pressure frequency response functions (PPRF) are gathered by using several input pressure pulses from the simulator and also horn an external signal generator. These PFRF are then used to get estimates of the catheter’s modal parameters. A two degree of freedom dynamic model is then adjusted to the measured PFRP and this model is then used to correct the input pressure distortions caused by the dynamics of the catheter. Paul0 S. Varoto