Final answer:
The best etiology to support the nursing diagnosis of ineffective airway clearance is bronchitis.
Step-by-step explanation:
The best etiology to support the nursing diagnosis of ineffective airway clearance in this case would be bronchitis. Bronchitis is an inflammation of the bronchi, which are the air passages that conduct air into the lungs. It is characterized by symptoms such as coughing, wheezing, and production of phlegm or mucus. In this scenario, the patient was diagnosed with bronchitis, congestive heart failure, and fever, and the nurse's assessment found peripheral edema and rhonchi, which are abnormal breath sounds.