It is important not to overlook this stage in the search process. Time spent identifying all possible synonyms and related terms for each of your PICO elements or concepts will ensure that your search retrieves as many relevant records as possible.
It might be useful to check relevant dictionaries, encyclopedias and key texts for alternate terms.
Build a list of each of the search terms you identify. For example, if you were searching for:
Exercise-based rehabilitation for coronary heart disease
Your list of synonyms and related terms might include:
physical education and training
(also consider specific forms of exercise)
Coronary heart disease
coronary heart bypass
coronary artery disease