PICC Care- cap change

I was wondering if anyone could give me some information about changing PICC line caps that have no clamps. Normally I would clamp the lines prior to changing the caps to prevent air from getting into the line. If there are no clamps wouldn't this be a concern?
Generally PICC lines without clamps, such as SOLO PICCs have no clamps because they are valved, so no, clamping should not be necessary in theory when changing the cap. That being said, I wouldn't leave the line uncapped for an unnecessarily long period of time when changing the cap.

As Muno appropriately stated, the IV catheters without an intregal clamp on the catheter itself, are usually Valved. Valved IV catheters will remain closed, in most cases, as long as negative pressure with withdraw, or positive pressure with flushing is not occurring. The only time that isn't the case, is when the valve is malfunctioning, such as a time when fibrin is preventing the valve from closing, or the valve is pushed up against something which is causing it to remain open, or malfunctioning.