A 5-point decline of forced vital capacity expressed as % predicted, over 6 months, is the current definition of disease progression (fast decline in lung function) in idiopathic pulmonary fibrosis. There is a need for techniques allowing to characterize disease progression earlier, so that treatment may be adapted as early as possible in the lack of a response.

Hypothesis. Our hypothesis is that 3-month changes of lung function parameters measured by a novel technique, impulse oscillometry, predicts 6-month changes in forced vital capacity in idiopathic pulmonary fibrosis.

A 5-point decline of forced vital capacity expressed as % predicted, over 6 months, is the current definition of disease progression (fast decline in lung function) in idiopathic pulmonary fibrosis. There is a need for techniques allowing to characterize disease progression earlier, so that treatment may be adapted as early as possible in the lack of a response.

Hypothesis. Our hypothesis is that 3-month changes of lung function parameters measured by a novel technique, impulse oscillometry, predicts 6-month changes in forced vital capacity in idiopathic pulmonary fibrosis.

Inclusion Criteria:

• Age ≥ 45 years.
• Idiopathic Pulmonary Fibrosis defined Interstitial Lung Diseases with 1) lack of any known cause for Interstitial Lung Diseases and 2) either the "definite usual interstitial pneumonia" pattern at CT scan, or the usual interstitial pneumonia (definite, probable or possible) pattern at lung biopsy, according to the Lung Function Group of the French Pulmonology Society criteria.

Exclusion Criteria:

• History of chronic obstructive airway disease.
• History of congestive heart failure.
• Emphysema-fibrosis syndrome, defined as emphysematous lesions involving >15% of the lung area at the level of the aortic arch (upper lobes).
• History of lower respiratory infection or acute respiratory failure of any cause less than 90 days before inclusion.
• Opposition to data processing.

Patients with Idiopathic Pulmonary Fibrosis