The purpose of this research study is to learn about how long hypertonic saline (HS) works in healthy subjects. Inhaled hypertonic saline is one of the medications used to treat Cystic Fibrosis (CF). In CF and more common lung diseases like chronic bronchitis, mucus builds up in the lungs. Hypertonic saline and other medications currently being developed may help patients with these lung diseases by speeding up mucus clearance from the lung. For these treatments to be effective, they likely need to be able to act for at lease several hours. Investigators are able to measure how lung treatments like hypertonic saline work by conducting a Mucociliary Clearance (MCC) scan. Currently, the investigators do not know how long hypertonic saline works in people who do not have CF. Investigators plan to use this information to improve the design and testing of new treatments for patients with chronic bronchitis.

Objectives:

1. The investigators will use MCC measurements to determine the durability of action of hypertonic saline in healthy (i.e. non-CF) subjects.
2. The investigators will determine the intra- and inter-individual variability of baseline MCC measurements using a slow inhalation/large particle protocol in healthy subjects to guide future sample size calculations.

Inclusion Criteria:

• Healthy subjects, without respiratory or cardiac comorbidities
• Age 18-55 years, inclusive
• FEV1 > 80% predicted and FEV1/FVC ratio >70%
• Non-pregnant female subjects must be either not sexually active, post-menopausal, surgically sterilized, or agree to use an appropriate "double-barrier" method (such as a diaphragm and condom); or, must currently be using a prescribed transdermal, injection, implant, or oral contraceptive during study participation
• Subjects who are capable of providing their written informed consent to participate in the study

Exclusion Criteria:

• History of smoking > 10 pack-years
• Any history of smoking within 60 days of screening
• Acute upper or lower respiratory illness within 30 days of screening
• Respiratory medication for any indication within 30 days of screening
• History of asthma, chronic bronchitis, or other chronic lung disease
• History of intolerance to hypertonic saline
• Women who are pregnant, lactating, or of childbearing potential who are unwilling to use an acceptable method of contraception throughout the duration of the study.
• Any condition that, in the opinion of the investigator, would potentially jeopardize the safety of the participant or the integrity of the study
• History of radiation exposure within the past year that would cause the subject to exceed limits for adults established by Federal Regulations
• Subjects who, in the opinion of the Principal Investigator, should not participate in the study

Healthy subjects of any ethnicity between 18-55 years of age, without respiratory or cardiac comorbidities, FEV1 greater than or equal to 80% predicted, FEV1/FVC ratio greater than 70%, non-pregnant female subjects, and subjects who are capable of providing their written informed consent.