Remote sensing tonometric catheter apparatus

Claim 1

A tonometric catheter apparatus for measuring a liquid fluid or gaseous fluid property indicative of the condition of an internal organ of a human or other mammal in vivo, comprising: (a) an elongated tonometric catheter tube having a lumen extending longitudinally therethrough, said tube being composed of a first elastomeric material that is substantially impermeable to one or more liquid fluids or gaseous fluids of interest, said fluids of interest including oxygen gases and carbon dioxide gases; (b) at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber being defined by a balloon member generally surrounding a portion of said tube and sealingly interconnected therewith, the wall of said balloon member being composed of a second material that is freely and selectively permeable to said one or more liquid fluids or gaseous fluids of interest, said second material being substantially impermeable to other liquid fluids or gaseous fluids, and said balloon member being inflated for forming an interior space between said balloon member and said catheter tube and for selectively positioning a portion of said balloon member substantially in direct contact with a wall portion of the internal organ in order to allow said one or more liquid fluids or gaseous fluids of interest from the tissue of the wall portion of the internal organ to permeate into said sampling chamber, with said tube extending to a position outside of the body of the human or other mammal, and with said lumen providing fluid communication between said sampling chamber and the outside of the body of the human or other mammal; (c) sensor means for sensing the level of at least one of said liquid fluids or gaseous fluids of interest from the tissue of the wall portion of the internal organ present within said sampling chamber, said sensor means being disposed within said sampling chamber; and (d) means for introducing a calibration fluid into said sampling chamber through said lumen in order to calibrate or recalibrate said sensor means while said balloon member is in said direct contact with the wall portion of the internal organ.