Abstract: A device for cooling a small area of skin over several cycles is used to measure the condition and efficiency of the capillary bed in returning the skin temperature to normal. The system has a heat exchanger which is attached to the skin. Controlled amounts of a low-boiling point liquid are injected into a cooling chamber. One side of the chamber has conductive material, which against the skin. The heat of the skin boils the liquid, which in turn cools the heat conductive material and the skin. A wick help carries the liquid to the heat conductive surface. A vessel stores the liquid. A movable divider separates the vessel into two spaces. The low-boiling point liquid is stored on one side of the divider. The second space contains a fluid having a significant higher vapor pressure then the first-mentioned fluid so that the pressure from the second fluid pressurizes the first fluid, keeps it in liquid state and drives it to the heat exchanger. Flow is controlled by a valve mounted in the heat exchanger.

Abstract: A heat exchanger changes the temperature of a predetermined area of the skin at a programmed rate preferably by cooling. The rate at which the area of skin changes in response to temperature change of the heat exchanger and the rate the skin temperature returns to normal are then measured and compared to standard rates over a number of cycles. Impaired peripheral blood flow is evident especially on subsequent cycles as vascular disease slows the rate of return to normal temperature of the skin. The heat exchanger has a cooling chamber with one side of the chamber being a cooling surface adjacent to the skin. An injector is connected to a source of fluid having a boiling point at ambient pressure less than the temperature to which the skin is to be cooled and greater than ambient temperature of the apparatus. The injector injects fluid into the chamber and onto the side of the cooling surface opposite the skin to boil the fluid on the surface to cool the surface and the skin.