The clinical diagnosis or evaluation of the disease needs to be performed by blood sampling. The blood sampling tests include routine blood, biochemical routine, coagulation, and even immune routine. The main reasons for failure to draw blood are as follows: 1. the patient is too obese, resulting in subcutaneous fat hypertrophy, and the superficial veins on the body surface are not obvious to touch, resulting in puncture failure. 2. the patient’s blood is too viscous, and after the blood collector is inserted into the blood vessel, the blood flow is slow, and even the blood cannot be extracted. 3. the patient with collapsed veins in critical patients, accompanied by hemorrhagic shock or infectious shock. Blood cannot be extracted even after the blood collector is inserted into the blood vessel, and deep venipuncture is needed.