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IPF is a type of interstitial lung disease. It is caused by lung tissue becoming thick and stiff and eventually forming scar tissue within the lungs. The scarring, or fibrosis, seems to result from a cycle of damage and healing that occurs in the lungs. Over time, the healing process stops working correctly and scar tissue forms. What causes these changes in the first place is unknown.
To understand IPF it helps to understand How the Lungs Work. In IPF, the scarring makes it difficult to breathe and deliver oxygen from the lungs to the rest of the body. In healthy lungs, oxygen passes easily through the walls of the air sacs, called alveoli, into your capillaries and bloodstream. However, in IPF, the scarring makes the walls of the alveoli thicker. The thickened walls of the alveoli make it harder for oxygen to pass into the blood.