A declaration shall be effective from the date of its execution until revoked in a manner prescribed by this chapter. Nothing in this chapter shall be construed to prevent a declarant from reexecuting a declaration at any time in accordance with the formalities of this chapter, including reexecution after a diagnosis of a terminal condition. If the declarant has executed more than one (1) declaration, then the latest declaration known to the attending physician shall take precedence. If the declarant becomes comatose or if the declarant's condition renders the declarant incapable of communicating with the attending physician, the declaration shall remain in effect during the comatose condition or until the declarant's condition renders the declarant able to communicate with the attending physician.