Many of these options are available either on the left side of the screen after a CINAHL search or in the CINAHL Advanced Search.
I like to start a search with broader terms and gradually narrow down my search, like an inverted pyramid. If you add in a term or limit and suddenly you get 0 results in a search that before gave you 2,000, something is wrong. Remove that last change and try something else.
The search in the image below reads (dnr OR "do not resuscitate" OR "resuscitation orders" OR "no code order")" AND (nurs* OR "healthcare professionals" OR "healthcare workers" OR "hospital staff") AND ethic*
Also highlighted in the image below are the "Advanced Search" link and the link to explore CINAHL Subject Headings mentioned above.