This study will compare the use of inhaled concentrated sodium chloride solution to an inhaled solution of sodium bicarbonate in an attempt to decrease the thickness and stickiness of the mucus in the lungs of a person with cystic fibrosis. Also, this study is also looking at whether or not it is possible to decrease the acidity of the airways by inhaling sodium bicarbonate through nebulizer treatments.

This study will compare the use of inhaled concentrated sodium chloride solution to an inhaled solution of sodium bicarbonate in an attempt to decrease the thickness and stickiness of the mucus in the lungs of a person with cystic fibrosis. Also, this study is also looking at whether or not it is possible to decrease the acidity of the airways by inhaling sodium bicarbonate through nebulizer treatments.

Inclusion Criteria:

1. FEV1 greater than 50% predicted.
2. Ability to spontaneously expectorate sputum (with or without chest physiotherapy).
3. Stable disease as defined by absence of exclusion criteria numbers 3-5 and clinician assessment.

Exclusion Criteria:

1. Reactive airway disease
2. Use of inhaled hypertonic saline in the past 28 days
3. Use of IV antibiotics in the past 4 weeks
4. Changes in CF-related medications in the four weeks prior to study screening
5. SpO2 < 94% on room air or use of supplemental oxygen.
6. Presence of untreated gastroesophageal reflux disease (GERD) or residual acid reflux symptoms in cases of treated GERD more than three times per week.
7. Pregnant or nursing females.