Final answer:
The nurse should first check the patient's O2 saturation when the endotracheal tube position has changed to ensure proper oxygenation, followed by reassurance and assessment of the patient's condition before informing the healthcare provider.
Step-by-step explanation:
When a nurse notes that a patient's endotracheal tube has shifted from the initial placement mark of 22-cm to the 25-cm mark, and the patient exhibits symptoms such as anxiety and restlessness, the first action the nurse should take is to check the O2 saturation. This is imperative to ascertain whether the patient's oxygen levels are within the normal range and to ensure that there is adequate oxygen exchange occurring in the alveoli of the lungs. The next steps would involve reassuring the patient, listening to breath sounds to detect any abnormalities, and notifying the patient's healthcare provider of the situation for further evaluation and management.