Engineering Considerations Of Catheters For Intravascular Ultrasonic Measurements (Englisch)

The mechanical properties of commonly used fluid transfusion or pressure monitoring catheters are similar to the properties required of catheters which include sensing devices. Consequently, bending and torsional stiffness of commercial catheters and tubes were measured at both room and body temperature. Five of these usually placed with the aid of fluoroscopy had an average Young's modulus of 5714x101 dyne/cm at 21°C which decreased 29% at body temperature; a shear modulus of 70.5x101 dyne/cm 4 at 21°C which decreased 13% at body temperature, and plastic deformation of 8% when loaded for 1 minute at 37°. Four of these were composed of a composite material. Catheters which are balloon directed during insertion had moduli values approximately 1/3 of these or less. The drag forces produced on balloons used on such catheters were measured for fluid velocities ranging from 10-50 cm/sec. Using this information the average force applied to a balloon throughout a cardiac cycle was calculated; values of 1280 dynes for a .6 ml balloon and 2490 dynes for a 1 ml balloon were found. The maximum wall thicknesses to catheter radii for single lumen catheters were determined for various material moduli which would allow the catheter tip to be directed by a balloon during its passage into the right heart.