Temperature sensing system with retrograde sensor

1. A system for measuring the temperature of a body fluid flowing within a body lumen at a location upstream of the insertion of a temperature probe into the body lumen, comprising:

a temperature probe having a proximal end, an intermediate region having a bend formed therein and a distal region, the distal region being proximal of the bend and having a distal tip with a temperature sensor mounted thereon; and

a sheath adapted for insertion into a body lumen, the sheath having a proximal end and a distal end, the sheath having

a central lumen having a proximal opening disposed at the proximal end of the sheath, a distal opening disposed at the distal end of the sheath and a central lumen axis extending from the proximal opening to the distal opening,

a capture tube attached to the distal end of the sheath, the capture tube having a distal opening adjacent the central lumen distal opening, a proximal opening, and a lumen extending therebetween, the lumen having a lumen axis parallel to the central lumen axis, the lumen having a length, the length selected to receive and protect the distal tip and at least a portion of the distal region of the temperature probe when the sheath and temperature probe are inserted into a body lumen; and

wherein retracting the proximal end of the temperature probe from the sheath causes the distal tip of the temperature probe to move in a proximal direction, moving the distal tip out of the proximal opening of the capture tube to a desired location proximal to the proximal opening of the capture tube without additional assistance.

2. The system of claim 1 , wherein the proximal end of the temperature probe extends into the distal end of the sheath and through the central lumen.