Your PubMed Search History is available on the Advanced Search page.
This page shows your search strategies and number of items found for each search.
The search statement numbers can be combined with each other or with new search terms using Boolean logic (e.g., #1 AND #2).
The video illustrates the directions that are on this page.
This video can be seen directly at http://www.nlm.nih.gov/bsd/disted/pubmedtutorial/videos/020_400.mp4