A heat exchange catheter comprising: a catheter body (21) having a proximal end, a distal end, a flow inlet lumen (24 or 26) and a flow outlet lumen (24 or 26)； a helically configured heat exchange balloon (28, 28a) connected to the flow inlet and flow outlet lumens so that the heat exchange fluid can circulate through the flow inlet lumen, through the balloon already through the flow exit lumen, said exchange balloon that has a wall thickness of less than 0.01651 mm (0.00065 inches) and that is foldable to a folded configuration that can be inserted into the vasculature of a human subject through a tubular introducer having an external diameter of not more than 5 mm and, thereafter, expandable to an expanded configuration having at least 125 cm2 of surface area of contact with blood； and a distal portion of the catheter body, which can be inserted into the vasculature of a human subject while the heat exchange balloon is in its folded configuration and the heat exchange balloon can be expanded to its expanded configuration by the circulation of fluid from thermal exchange through this； the heat exchange balloon, when placed in the vasculature of an adult human subject in said expanded configuration with circulation of cooled heat exchange fluid circulating therethrough, being able to exchange sufficient heat with the blood flowing from the subject to cause the subject's core body temperature to drop from normothermia to 34 degrees C or less in 30 minutes.Un catéter de intercambio de calor que comprende: un cuerpo de catéter (21) que tiene un extremo proximal, un extremo distal, un lumen de entrada de flujo (24 o 26) y un lumen de salida de flujo (24 o 26)； un balón de intercambio de calor configurado helicoidalmente (28, 28a) conectado a los lúmenes de entrada de flujo y de salida de flujo de manera que el fluido de intercambio térmico pueda circular a través del lumen de entrada de flujo, a través del balón y a través del lumen de salida de flujo, dicho balón de i
