This experiment is designed to test the effectiveness of a new electronic nose device, which allows a non-invasive breath test for markers of lower respiratory tract infection, which may predict the probability of bacterial organisms in the lower respiratory tract. It consists of:

• A breath collection apparatus for collection of volatile organic compounds in breath onto a sorbent trap and Tedlar bag, as well as for the collection of a separate sample of room air.
• Analysis of the volatile organic compounds in breath and room air by short acoustic wave/gas chromatography.
• Interpretation of the volatile organic compounds with a proprietary algorithm in order to predict the probability of lower respiratory tract colonization and infection.

This study will test the hypothesis that the investigators can identify the presence of Pseudomonas aeruginosa by sampling the "head space" above culture media of sputum provided by patients with cystic fibrosis. This study will test the additional hypothesis that the investigators can identify the presence of Pseudomonas aeruginosa by sampling exhaled breath from the patient providing the sputum.

Inclusion Criteria:

• Clinical diagnosis of Cystic Fibrosis
• Must be able to give breath and sputum samples

Exclusion Criteria:

• Heavy smoker
• Inability to regularly give breath and sputum samples
• History of additional pulmonary disease

Patients will be selected from Dr. Landon's primary care clinic.