US Patent 7156840 Pressure monitor for cryoablation catheter

A cryoablation device having a pressure monitoring system includes an elongated catheter tube that has a central lumen and is formed with a closed distal end. The distal end of a refrigerant supply line is positioned in the central lumen and distanced from the catheter tube's distal end to establish an expansion chamber therebetween. A return line, which can be established between the supply line and the catheter tube or can include a return tube, is provided to exhaust expanded refrigerant from the chamber. First and second pressure sensors are respectively positioned in the supply line upstream from the expansion chamber and in the return line. Typically, both sensors are positioned to remain at extracorporeal locations throughout a cryoablation procedure. Measured pressures are used together with the supply and return line dimensions to analytically estimate the chamber pressure and allow the expansion of refrigerant in the chamber to be monitored.