Pneumonia is a significant global and national health issue, particularly posing a notable threat to elderly population. Accumulation of sputum in pneumonia patients often results in impaired airway clearance, negatively impacting disease management and recovery. Clinically, nebulization therapy is widely employed to facilitate sputum clearance; however, evidence regarding the comparative effectiveness of different nebulized solution concentrations remains limited and inconsistent. Therefore, this study aims to evaluate and compare the clinical effects of nebulized solutions with various osmotic concentrations (3% hypertonic saline, 0.9% normal saline, 0.45% hypotonic saline, and distilled water) on airway clearance in patients with pneumonia. A randomized, double-blind controlled trial design will be used, recruiting 80 patients with pneumonia from a regional teaching hospital in northern Taiwan. Participants will be randomly assigned into four groups, receiving nebulized therapy four times daily over a period of seven days. This study outcome including the length of hospital stay, venous blood gas analysis, routine sputum examination, and arterial oxygen content. The findings of this the study are anticipated to provide evidence-based recommendations for the clinical application of nebulized solutions with different concentrations, aiming to enhance airway clearance efficiency, improve clinical care outcomes for pneumonia patients, and serve as a practical reference for healthcare professionals.