Abstract: A syringe comprising a barrel having a needle extending from a needle end of the barrel, a plunger and a protective sleeve. There is a groove in the inner surface of the sleeve and a key extending from the outer surface of the barrel into the groove. The groove has a longitudinal section and a circumferential section. The circumferential section has opposing and offset zig-zag edges. A spring biases the barrel toward the protective sleeve. By pressing the plunger against the force of the spring, the key moves in the groove, sliding along the zig-zag edges. The design of the groove cooperates with the operation of the syringe and can cause the key to move into the longitudinal groove and the needle to thereby retract into the protective sleeve after the plunger is depressed.

Abstract: An apparatus for monitoring EKG information includes a programmable apparatus carried by an ambulatory patient for performing continuous, real-time analyses of EKG information derived from the patient. The apparatus facilitates the determination of the existence of various conditions based on these analyses which portend cardiac complications including myocardial ischemia, and arrhythemia activity and further instructs the patient on the manner of treatment required for the detected condition.