A device for positioning a needle tip to a desired location by signaling pressure change is provided. The device includes a barrel, a piston, a biasing element, and a plunger. The barrel defines a reservoir, and it includes a distal end connectable to a puncturing apparatus. The plunger is slidably engaged with the piston, and both are movable within the reservoir. The biasing element connects the plunger and the piston, and its change in length corresponds to the relative position of the plunger and piston. In operation, the piston is at a first position relative to the plunger when the biasing element is at a first length. The piston later moves to a second relative position in response to the biasing element's change of the length resulting from a pressure change inside the reservoir when the puncturing apparatus reaches a location of a mass. The position's change of the piston is visually detectable.
