SFTPD and idiopathic pulmonary fibrosis: The distance in the 6-min walking test [20] and high serum levels of Krebs von den Lungen-6 [21], Surfactant protein-A and Surfactant protein-D [22], and neutrophil counts in bronchoalveolar lavage [23] have also been reported as prognostic factors for IPF; however, to the best of our knowledge, this is the first report describing the impact of respiratory impedance measured by the oscillometry on survival in patients with IPF.