Patent ID: 7842031

Claim:
A method for determining fluid egress comprising: positioning a catheter at a tissue treatment site, the catheter comprising: a shaft having a proximal portion, a distal tip, and at least one fluid pathway therebetween; an expandable element defining a cooling chamber therein in fluid communication with the at least one fluid pathway; a first electrode located on an exterior surface of the shaft between the proximal portion and the expandable element; and a second electrode located on the exterior surface of the shaft between the expandable element and the distal tip; applying an electrical current between the first and second electrodes to form an electrical field about the expandable element; measuring impedance between the first and second electrodes; and correlating the measured impedance to a condition of fluid egress from the cooling chamber to a point exterior to the catheter, and generating a signal indicating the condition of fluid egress from the cooling chamber to the point exterior to the catheter.