A medical instrument having an aspiration needle and a protective needle cap. The cap protects a scope from damage due to needle insertion. The cap is placed over the end of a needle before insertion into an endoscope (e.g., bronchoscope) before use in a patient. The cap includes a first section having a first cross-sectional dimension based on an outside diameter value of a distal end of a medical device used in an endoscope and a second section having a second cross-sectional value that is smaller than the first cross-sectional value. A connection force exists between the first section and the distal end of the medical device, the connection force being greater than a frictional force between the device and an interior wall of an endoscope as the medical device is moved within the endoscope.
