Help needed with PICCs

I have found a couple of things to help, but sometimes it just isn't going to happen...

--try having them reposition the arm...straight out beside them, above the head, etc. Do this while pt is laying down, then try with pt sitting up if needed.

--try having them cough then using different arm positions.

--have pt lay on their side

--last ditch, sometimes 1 cc of heparin put into the lumen and left for 15 minutes or so will help.

I find attempting to draw from anything less then a 4 french can collapse the lumen, and , while there is some blood return, it can still be difficult to get enough for an adequate sample.

My 'tricks' include:

1) inserting at least a #4 if I have the say in the beginning;

2) flushing vigorously with at least 20cc NS before withdrawing the waste;

3) repositioning the arm- rotating it sometimes will free the line from a trapped position between muscles;

4) having the patient take a deep breath and hold it for a few seconds, then withdrawing just as they start to exhale:

5) being sure that the patient/caregiver knows to flush the line properly, using positive pressure when clamping (seems to be frequently missed point with many of the patients I see).

4) having the patient take a deep breath and hold it for a few seconds, then withdrawing just as they start to exhale:

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What's the mechanism behind this? Something about changing intrathoracic pressure??