Pneumonia may increase bronchial secretion and decrease mucociliary function, thereby causing lung atelectasis. Patients with acute pneumonic respiratory failure receiving mechanical ventilation may therefore have a large amount of pulmonary secretions, thereby worsening bronchial hygiene, oxyhemoglobin saturation and ventilation-perfusion match. Cough function is paramount for expectoration; however, coughing is not practical for patients with endotracheal intubation and sedation. High frequency chest wall oscillation (HFCWO) may dislodge airway secretions as efficiently as conventional chest physical therapy (CCPT). However, pneumonia is not currently an indication for chest physical therapy.