Blood extraction from lancet wounds using vacuum combined with skin stretching.

Key factors and practical limits of blood extraction from lancet wounds on body sites other than the finger were determined by testing a large number of conditions. During these tests, the pain associated with lancing alternate body sites was rated as less painful than a fingerstick 98% of the time. Vacuum combined with skin stretching was effective in extracting an adequate volume of blood from the forearm for glucose testing, up to an average of 16 microl in 30 s. The amount of blood extracted increases with the application of heat or vacuum before lancing, the level of vacuum, the depth of lancing, the time of collection, and the amount of skin stretching. Vacuum and skin stretching led to significant increases, up to fivefold in the perfusion of blood in the skin as measured by laser Doppler. Our observations suggest that vacuum combined with skin stretching increases blood extraction at alternate sites by increasing the lancet wound opening, increasing the blood available for extraction by vasodilatation, and reducing the venous return of blood through capillaries.