Device for shielding a sharp tip of a cannula and method of using the same

1. A method of shielding a sharp tip ( 28 ) of a cannula ( 20 ) at least partially defining an interior passage including first and second opposite ends, the method comprising:

collecting a sample of tissue from a patient in the passage of the cannula;

inserting a shaft ( 55 , 155 ) into the passage through the first end thereof to push the sample out of the second end of the passage to collect the sample, the step of inserting including shielding the sharp tip of the cannula with a shield ( 48 ) when the shaft is inserted a predetermined distance into the cannula; and

retaining the shaft relative to the cannula against movement out of the passage through the first end so as to hold the shield over the sharp tip;

wherein the step of inserting the shaft ( 55 , 155 ) into the passage further includes retracting a catch ( 60 , 160 ) mounted on the shaft as the catch contacts the first end of the cannula so that the catch is nearer to the shaft for movement of the shaft through the passage of the cannula ( 20 ); and

wherein the step of retaining the shaft ( 55 , 155 ) includes extending the retracted catch ( 60 , 160 ) to a position in which the catch projects out from the shaft as it exits the second end of the passage.

2. A method as set forth in claim 1 wherein the step of retaining the shaft ( 55 , 155 ) comprises extending a catch ( 60 , 160 ) for engagement to retain the shaft in the passage.

3. A method as set forth in claim 2 further comprising releasing the catch ( 60 , 160 ) to permit the shaft ( 55 , 155 ) to be withdrawn from the passage.

4. A method according to claim 1 wherein the step of inserting the shaft into the passage includes inserting the shaft into the distal end of the cannula, wherein the sharp tip is formed on the distal end of the cannula.

5. A method according to claim 1 wherein the tissue includes bodily fluid.