Comparison of Airway Clearance Efficacy of Two High Frequency Chest Wall Oscillation (HFCWO) Devices in Cystic Fibrosis

Patients with cystic fibrosis (CF) must perform daily bronchial drainage therapy (BD) to keep their airways clear of secretions. Many different techniques are available to achieve this and there is currently no agreement as to which form of therapy is most effective. High frequency chest wall oscillation (HFCWO is used for this purpose by CF patients throughout the United States and abroad. To perform this therapy, the patient wears a vest which fits over the entire torso and is connected to an air compressor. The compressor generates oscillating air pulses that are transmitted to the lungs, thereby mobilizing secretions. The oscillations produced by the most commonly used device have a sinusoidal wave form (The Vest™ Airway Clearance System, Hill-Rom Inc, St Paul, MN). Previous studies indicate this form of therapy is as effective as more traditional and cumbersome forms of therapy. The design of the pulse generator has been recently modified so that the oscillations produced have a triangular wave form (Respitech Inc, MN). Studies done at the University of Minnesota found that the air flows induced in the airways can vary substantially depending on the wave form applied to the chest. At present, the impact of using a triangular wave form on mucus removal is unknown. The proposed study will compare mucous clearance using a device generating sine wave oscillations to a device generating triangular wave oscillations. Hypothesis: Bronchial drainage using a triangular wave form of HFCWO will result in superior sputum production compared to HFCWO using a sine wave form. Secondary Hypotheses: Bronchial drainage using a triangular wave form of HFCWO may result in sputum with rheologic properties distinct from sputum produced while using sine wave HFCWO. Bronchial drainage using a triangular wave form of HFCWO may result in superior post-therapy pulmonary function tests compared to pulmonary function tests obtained following therapy with sine wave HFCWO. Subjects will perceive bronchial drainage using a triangular wave form of HFCWO as more comfortable than airway clearance using sine wave HFCWO.