Well you should read this FAQ to assist with your research
The points which I think you need to focus on
== Secrecy vs. Integrity: What are you trying to protect?
I would imagine that for patient information, you would want to make sure that the messages are authentic.
Undetected tampering with the message is at least as serious as unwanted disclosure.
== Keys vs. Passphrases
They may have a 256 bit key, but your users are going to be using typically quite short pass phrases. If they use the passphrase as the key (this is a big NO-NO), then a passphrase of "fred" is about 10 bits, not 256 bits.
== Secret Algorithms
Their web page mentions "the Atlantis encryption function". Is this secret, or is it an implementation of one of the standard algorithms like DES?
== Recoverable Keys
Ask if they have any means to recover an encrypted message. If they have, then it isn't secure.
Personally, I would use a specific encryption product like PGP just for the encryption. If you like the word processor as a word processor, thats fine - but verifying its encryption credentials could be rather more difficult, with no guarantee of a passing grade.