long as desired as is controlled by the user the bladder 382 is connected and supplied inflation gas thereto from the gas source 380 by lines 381 381 or multiple lines not shown from the gas source 380 multiple gas sources are also permissible the lines 381 381 may be permanently attached but are preferably removably connected the lines 381 381 connect to the outer bladder layer 384 via airtight ports not shown the ports preferably include valves not shown such as a check valve or stop cock to prevent escape of gas from the bladder 382 once the lines 381 381 are disconnected or to permit the input or discharge of gas as desired the ports may be located anywhere along the outer bladder layer 382 the inner and outer shells 336 338 and the outer bladder layer 384 are preferably made of a material impervious to liquid and gas thermoplastic elastomers tpes which can be made into film or sheeting by extrusion casting calendering or other manufacturing processes are appropriate included among these tpes are polyurethane copolyesters styrene copolymers olefins and elastomeric alloys preferred tpes will have good elongation and tear strength good resistance to flex fatigue at both low and high temperatures good dynamic properties resist water alcohols and dilute bases and acids and exhibit good thermal conduction properties to permit the rapid transfer of heat from the person or cadaver the materials for the inner and outer shells may also comprise teflon u00ae tyvek u00ae or gore tex u00ae type materials or the like the material of the inner shell may include microscopic pores these microscopic pores permit.