The person who creates a power of attorney is the principal and the person the principal names to act on his/her behalf is the agent.  The agent's authority to act on behalf of a principal is derived from the Power of Attorney Act.   Once the agent's authority is established by the creation of a power of attorney document, third parties, including health care providers, are required to honor the agent's decisions.  Third parties are not obligated to comply with agent's decisions unless they are aware of the agent's status under the power of attorney. 

The agent is granted the same rights as a spouse or adult child of the principal to visit the principal in a hospital or other institution, regardless of the institution's rules to the contrary  &55 Illinois Compiled Statutes 45/4-10.