[Development of a computer-assisted thermoelectric Peltier cold test procedure with integrated photoplethysmography unit for noninvasive evaluation of acral skin circulation].

Local cold provocation tests are an important, non-invasive diagnostic tool for collecting information about skin perfusion during exposure to cold. In patients suffering from vasospastic circulatory disorders such as Raynaud's phenomenon, it is of particular importance to be able to collect data about acral circulation during the cooling test in the asymptomatic intervals between naturally occurring attacks. By carrying out a series of cold provocation tests, for example, patient response to a newly initiated therapy can be assessed. Here we present a recently developed, computer-aided thermoelectric Peltier device with an integrated finger holder for carrying out local cold provocation tests. The electronic control unit of the Peltier element make it possible to cool or heat to predefined temperatures. At the same time, the temperature of both the finger holder and the skin can be measured. A photoplethysmographic sensor is also integrated within the device, enabling the response of the pulse waves to the controlled temperature changes to be monitored accurately. It is also possible to measure simultaneously laser Doppler flux and capillary pressure in the nailfold and to perform nailfold capillaroscopy to determine red blood cell velocity. The new device provides us with the technical means to study the interrelationship between acral skin perfusion and the thermal regulation of the skin.