 The hypothesis being tested is that HS will rehydrate CF airway secretions, producing a sustained acceleration in MCC in young children with CF, regardless of whether a measurable mucus clearance defect exists at this relatively early stage of disease. We predict a substantial acceleration of MCC will reduce the exacerbation rate in young children with CF. In addition, with the growing number of treatment modalities that are prescribed to patients with CF, adherence to complex and time consuming medical regimens becomes increasingly problematic and important. We therefore, wish to test an improved drug delivery platform for HS- the eFlow Pari Pharma vibrating mesh nebulizer, which has the potential to reduce treatment times, improve compliance, and increase treatment efficacy. 