As Paul says the only sure way is to visit everyday and make sure he is being given the proper and needed care. Unfortunately, here in the USA, the nursing home system is inadequately regulated and monitored.

If you can not be there everyday maybe you can trade off with someone else or at least try to get in good relations with a supervisor or a aide who will give you a few minutes each day on the phone to check in and get an honest update.

You just need a real person who can watch out, sad but true.