Many times, it may seem like you aren't able to find any good articles using the keywords that you've chosen. This could be that your chosen keyword has many meanings, or simply that the database doesn't recognize your term. The good news is that there is another way to search, and it's called subject heading searching.
Subject headings are words that are used by the database developers to describe the content of an article or other information. You may also hear them referred to as descriptors, headings, or index terms. They work in much the same way that tags work on social networking sites, and that is, by describing and organizing content. But unlike their "tag" counterparts, subject headings are not set by the user, but by the database publisher. They are the "controlled vocabulary," or limited set of words used to establish order and provide access points for articles and other information. Controlled vocabularies are specific to individual databases, but are usually available within each database under links such as "thesaurus," "headings," or "subjects."
Both CINAHL and PubMed use a controlled vocabulary. CINAHL calls its thesaurus "CINAHL Headings" and PubMed calls its thesaurus "MeSH," which stands for Medical Subject Headings. Because CINAHL was modeled after PubMed, you will notice that they share many similar features and functions.