What is the most important intervention to prevent respiratory complications in postoperative patients?

Postoperative respiratory complications arise from alveolar hypoventilation, atelectasis formation, impaired mucociliary clearance, and reduced lung expansion due to anesthesia effects, pain-related shallow breathing, and immobility, leading to decreased functional residual capacity and impaired gas exchange. Rationale: A. Administering intravenous fluids supports circulatory volume but does not directly prevent pulmonary complications such as atelectasis. Excess fluids may even worsen pulmonary edema in susceptible patients. Therefore, it is not the primary preventive respiratory intervention. B. Routine supplemental oxygen therapy is not indicated for all postoperative patients unless hypoxemia is present. It does not prevent atelectasis or improve lung expansion mechanics. Oxygen corrects hypoxia but does not address underlying ventilation issues. C. Deep breathing exercises and incentive spirometry promote alveolar expansion, prevent atelectasis, and improve ventilation-perfusion matching. They enhance lung inflation, mobilize secretions, and maintain functional residual capacity. This is the most effective intervention for preventing postoperative respiratory complications. D. Early ambulation improves overall pulmonary function and circulation, but it is secondary to active lung expansion techniques in immediate postoperative care. It supports recovery but does not directly target alveolar collapse as effectively as incentive spirometry.