You can search many resources, especially library databases, more successfully by typing in keywords rather than phrases or sentences.
Why? Because computers do not think. But computers are good at matching your words with words in the records in the database.
High blood pressure AND doctors AND medicine
gives different results than
Hypertension AND physicians AND drugs
Try it in CINAHL
You may want to start your research by reading up on a topic. You may want to consult an encyclopedia--for example the Gale Encyclopedia of Medicine, available under the databases link in the Search UM Libraries box on the right hand side of the box.
You might want to read a literature review or meta-analysis article in a database such as CINAHL.
To see a video on locating a literature review or meta-analysis, check here.
Both of these approaches will help you explore issues involved and the language used in explaining your topic.
Put terms or short phrases on different lines in databases. Then examine your results to see if there are other relevant terms. Look especially at the subjects that are assigned to the records. These are the "language of the database." Include these terms in your searches. In most databases there will be a box to check to limit your research to peer-reviewed (scholarly) sources. You can see the full-text immediately, check to see if it is in another database, or order through Interlibrary Loan.
Here is a short video which will illustrate this. Searching CINAHL.
Reviewing the records will help you refine your topic--you'll see areas that have been well researched and areas which have not been.