It is the goal of the proposed study to compare the efficacy, as assessed primarily by sputum weight, of these two different devices (the Electroflo 500 and the G5 Flimm-Fighter) for airway clearance (AC) in CF patients with mild to moderate lung disease, who have stable lung health and perform AC at home as part of their routine therapeutic regimen.

The investigators hope to enroll 25 patients with cystic fibrosis (with daily sputum production) in this study. It is the goal of the proposed study to compare the efficacy, as assessed primarily by sputum weight, of these two different devices (the Electroflo 500 and the G5 Flimm-Fighter) for airway clearance (AC) in CF patients with mild to moderate lung disease, who have stable lung health and perform AC at home as part of their routine therapeutic regimen.

Inclusion Criteria:

1. Diagnosis of CF established by standard criteria (sweat chloride > 60 mmol/L and/or two alleles affected by gene mutations know to be associated with CF).
2. Age older than 8 years.
3. Known to consistently produce sputum.
4. Currently on a home therapeutic regimen that includes some form of AC performed at least 1 time daily.
5. FEV1 > 30%-predicted, and with stable lung function

Exclusion Criteria:

1. Hospitalization for CF pulmonary complications in the 1 months preceding enrollment.
2. Hemoptysis > 60 cc in a single episode in the 4 weeks preceding enrollment.
3. Chronic chest pain.
4. Participation in another interventional clinical trial in the previous 30 days.

All participants had the diagnosis of cystic fibrosis. All enrolled had baseline sputum production and were deemed at their baseline health status.