HFCWO was performed using a VestTM Airway Clearance System Model 105 (Hill-Rom, St. Paul, Minnesota) connected to a vest via two flexible tubes by trained nurses who were blinded to the purpose of the study. All of the nurses had been well trained in how to perform both HFCWO and CCPT before the study, as these procedures are routinely performed by nurses at the investigators institution. HFCWO was applied to each subject at a frequency of 10-12 Hz and a pulse pressure setting of 1-2 selected from a scale ranging from 1 to 10 (arbitrary units) for 15 minutes. The patients receiving HFCWO were placed in a semi-upright sitting position, and the patients undergoing CCPT received cup-hand percussion with the hands positioned 3 inches from the chest, striking the chest with a waving movement while they were placed in right and left decubitus positions for 5-10 minutes each1. Following HFCWO or CCPT, suction was performed immediately via an endotracheal tube.