A needle puncture system for automatic blood sampling

As a part of automatic blood sampling system, we developed equipment for needle puncture that measured force acting on the needle tip and electric impedance between inside of the needle and skin of the subject. To obtain the needle tip pierced into the blood vessel, the changes in puncture force (PF) and electric impedance (EI) were evaluated. The puncture experiments were carried out on the vein of a rabbit's ear. The PF increased gradually when the tip of the needle touched the skin. Then some peaks in PF, caused by piercing the skin and the vessel wall, were observed. When the needle punctured the vein, blood flowed into the needle and caused a short circuit of EI measurement. We have shown that the combination of PF and El will provide information to realize automatic blood vessel puncture.