Apparatus and methods for cooling liquid coolant, such as nitrous oxide, to be delivered to a cryo-ablation device such as a balloon catheter. A hose or conduit in fluid communication with the ablation device includes an outer member and inner tubes. A first inner tube disposed within a lumen of the outer member carries liquid coolant to the ablation device. Another inner tube also disposed within the lumen carries liquid coolant and terminates within the lumen such that gaseous coolant derived from liquid coolant flowing through the second inner tube flows within the lumen to cool or chill the first inner tube and liquid coolant carried by the first inner tube to the ablation device.