A heating element includes an electrically insulating layer; resistive layer formed of a positive temperature coefficient material; and an electrically conductive layer disposed between the electrically insulating layer and the resistive layer and including a first bus and a second bus that is spaced apart from the first bus, the resistive layer electrically connecting the first bus and the second bus. The electrically insulating layer, the electrically conductive layer, and the resistive layer are stacked to form a lamination and the lamination having a thickness and a width and length extending orthogonal to the thickness. The lamination may have slits extending through the thickness thereof and along a portion of the length thereof. Terminals may be connected to the buses and arranged to provide a counter current flow pattern across the lamination. The lamination may be used in a warming device and in connection with a patient warming system.