Patent ID: 7300453

Claim:
A catheter system to determine pressure in a catheter for use in the system to change the temperature of blood by heat transfer to or from a circulating working fluid, comprising: a supply lumen to introduce a circulating working fluid to a heat transfer element wherein said supply lumen is substantially straight through the heat transfer element; a helical return lumen, helically encircling the substantially straight supply lumen, to extract a circulating working fluid from the heat transfer element, the return lumen having a cross-sectional area greater than the cross-sectional area of the supply lumen to enhance flexibility of the heat transfer element, wherein the helical return lumen encircles the supply lumen such that blood flows between the helical return lumen and the supply lumen, and wherein turbulence is induced in a substantial portion of a free stream of blood by contact with both the helical return lumen and the supply lumen, and a pump for circulating fluid through the supply lumen and helical return lumen to change the temperature of the heat transfer element to a temperature different from a patient temperature, to heat or cool the patient, wherein the pump speed and current drawn by the pump are used in a calculation of pressure.