(a) This section applies when an adult qualified patient has executed or issued a directive and is incompetent or otherwise mentally or physically incapable of communication.
(b) If the adult qualified patient has designated a person to make a treatment decision as authorized by § 166.032(c), the attending physician and the designated person may make a treatment decision in accordance with the declarant’s directions.

(c) If the adult qualified patient has not designated a person to make a treatment decision, the attending physician shall comply with the directive unless the physician believes that the directive does not reflect the patient’s present desire.