Two-stage fluid medicament jet injector

Abstract

A jet injector, and a method, for injecting fluid medicament into a patient in a two-stage process. During the first stage fluid is expelled from the injector under relatively high pressure, to create a hole through the skin of the patient. During the second stage, fluid is infused through the hole into the patient at a much lower pressure, and for a much longer period of time. The jet injector includes a syringe unit, and a drive mechanism which is selectively connectable with the syringe unit. Specifically, the drive mechanism includes two springs which are positioned to urge against a push rod as they elongate. When the drive mechanism is engaged with the syringe unit, the push rod is positioned longitudinally co-linear with a plunger in the chamber. When the springs are released, they push the push rod which, in turn, pushes the plunger, causing the fluid to be expelled through an injection tube connected to the chamber. The syringe unit also includes a suction compartment for pulling the skin against a syringe tip at the end of the injection tube. To prepare the injector, the chamber of the syringe unit is filled with a fluid medicament, the drive mechanism is cocked, and the syringe unit is engaged with the drive mechanism. A vacuum source is then connected in fluid communication with the suction compartment. The syringe tip and the opening to the suction compartment are then pressed against the skin, and the injector is activated.