The most common postoperative respiratory problems are atelectasis, pneumonia, and pulmonary emboli. Pneumonia is the inflammation of lung tissue that causes a productive cough, dyspnea, and crackles. Pulmonary edema usually results from L-sided heart failure, and it can be caused by medications, fluid overload, and smoke inhalation. CO2 retention results from the inability to exhale CO2 in clients w/conditions such as COPD. Fluid imbalance can be a deficit or excess related to fluid loss or overload.