Abstract: This is a catheter assembly which may be used in accessing a tissue target within the body, typically a target which is accessible through the vascular system. Central to the invention is the use of a braided metallic reinforcing member, typically of a stainless steel or super-elastic alloy ribbon, situated within the catheter body in such a way to create a catheter section having a thin wall, controlled stiffness, and high resistance to kinking. The distal-most section of the catheter is much more flexible than are other braided catheters of the genre due to choice of braid construction features of that distal-most section. The distal-most braid, and optionally, intermediate braid components are constructed to be more flexible than the more proximal sections due to deletion of ribbons from the braid structure, change of ribbon material, and change of pitch. The various sections include braids which may have a consistent pitch or may vary in pitch along the axis of the catheter or catheter section.

Abstract: A multi-lumen, multi-purpose cardiac catheter which incorporates optical filaments and an optical coupler for use with external apparatus for determining the oxygen concentration in the blood of a patient under critical care conditions, as well as incorporating therein a thermal element useable with a second external apparatus for measurement of continuous cardiac output. The thermal element is disposed at a necked down portion of the catheter at the distal end thereof, with at least one of the lumens of the catheter substantially compressed at the necked down portion thereof. The catheter also includes a thermistor and at least one injectate port for enabling the user to also conduct thermal dilution readings and obtain intermittent measurements of cardiac output. The combination of a thermal dilution catheter with a SVO.sub.