Final answer:
When assessing the respiratory system for complications of immobility, the nurse should focus on auscultating the entire lung region to assess lung sounds.
Step-by-step explanation:
When assessing the respiratory system for potential complications of immobility, the nurse should focus on auscultating the entire lung region to assess lung sounds. This is because abnormalities in lung sounds can indicate respiratory problems and allow for early intervention. Inspecting chest wall movements primarily during the expiratory cycle, focusing auscultation on the upper lung fields, and assessing the patient at least every 4 hours are not specific actions related to assessing respiratory complications of immobility.