Fig 2. Ultrasound-guided DNTP technique.

The radial artery (RA) was identified in an out-of-plane approach with an ultrasound probe. (A) The needle was inserted through the skin, and the needle tip (arrowhead) appeared as a hyperechoic dot on the display. (B) The probe was moved slightly further without moving the needle, and the hyperechoic dot disappeared as the needle tip exited the ultrasound plane. (C) The needle was advanced toward the radial artery with the probe held in place, and the needle punctured the radial artery. (D) The probe was moved proximally again, and the needle tip disappeared from the display. (E) The needle was advanced, and it was confirmed that the needle tip remained in the radial artery. Arrowheads on the ultrasound images indicate the needle tip of the angiocatheter. DNTP, dynamic needle tip positioning.