A declaration shall become operative when (1) it is communicated to the attending physician, (2) the declarant is determined by the attending physician to be in a terminal condition or in a persistent vegetative state, (3) the declarant is determined by the attending physician to be unable to make decisions regarding administration of life-sustaining treatment, and (4) the attending physician has notified a reasonably available member of the declarant’s immediate family or guardian, if any, of his or her diagnosis and of the intent to invoke the patient’s declaration. When the declaration becomes operative, the attending physician and other health care providers shall act in accordance with its provisions or comply with the transfer requirements of section 20-409.