Detection of needle puncture to blood vessel by using electric conductivity of blood for automatic blood sampling

Although blood sampling is frequently performed, a system to take blood sample automatically has not yet been developed. To achieve needle control for automatic blood sampling, the changes in puncture force and electric conduction by blood were evaluated. An injection needle with electric conduction electrode was set on a device for measuring puncture force by using a loadcell. When the needle punctured a blood vessel, blood flowed into the needle and caused a short circuit between electrodes attached on the skin surface and inside of the needle. Totally 18 of puncture experiments were carried out on vein of a rabbit's ear. The peak of puncture force caused by piercing the vessel wall and the electric conduction by the blood, were simultaneously observed in successful cases. When the needle pierced the vein out, no peak of puncture force but the electric conduction of the blood was obtained. This result shows that the electric conduction by blood can be applied to control needle insertion to the vein for automatic blood sampling.