Inclusion Criteria:

• Adult patients ≥ 18 years old.
• Fulfilling the American College of Rheumatology criteria for SSc.
• For ILD subgroup (n=6):
  • An upright chest-roentgenogram (chest x-ray) is abnormal and compatible with an interstitial lung disease.
  • HRCT of the chest confirms the presence of bilateral reticular, ground glass, and/or honeycomb abnormalities that is otherwise unexplained by an alternative process
  • The HRCT fibrosis score must be ≥ 7.
  • The total lung capacity (TLC, measured by body plethysmography) and/or the diffusing capacity of the lung for carbon monoxide (DLCO) is below the predicted normal.
  • The forced vital capacity (FVC) is reduced below the predicted normal.
  • The patient is symptomatic (i.e. dyspnea and/or a chronic cough) for more than 8 weeks that is otherwise unexplained by an alternative mechanism.
• For No ILD subgroup (n=6):
  • No radiographic evidence of ILD on plain chest x-ray.
  • The HRCT fibrosis score, when performed) must be < 7
  • The TLC and FVC are within their predicted normal.
  • The DLCO is within the predicted normal, except when reduced in isolation by pulmonary hypertension.

Exclusion Criteria:

• Active smoking within the 6 months.
• Pneumonia or bronchitis in past 4 weeks.
• Active acute illness such as uncontrolled heart failure, infection, or asthma.
• Use of more than 3 liters per minute (LPM) of oxygen by nasal cannula at rest.
• Coordinator, investigator, or clinician concerns on the patient's compliance, safety, or in ability to complete study requirements.
• Morbid condition not expected to live more than 1 year.
• Alternative cause or diagnosis for the patient's ILD besides SSc.
• Pregnancy.
• Obstructive lung disease with an FEV1 (forced expiratory volume in 1 second) to FVC ratio less than 0.7, nor radiographic evidence of emphysema on CT.
• Planned therapeutic procedures involving the esophagus (e.g. dilation, surgery) prior to completion of study tests