an enclosure including an interior and an exterior, the enclosure closed on one end and open on the other end and sized and shaped to receive the patient's extremity, the enclosure defined by a collapsible bag including two sheets of fluid impervious material sealed together, a first side of one sheet defining the exterior of the enclosure, a first side of the other sheet defining the interior of the enclosure, the sheets further forming a plurality of pockets such that gas can be delivered to the pockets to inflate and maintain the enclosure in a substantially rigid condition when treatment gas pressure in the interior of the enclosure is cycled between first and second pressures.