Th e incidence of IPF exacerbations varies greatly between studies (from 8.5% to 60%) mainly because of diff erences in their design [3] [4] [5] [6] 8, 14, 16, 19, 28, 29, [31] [32] [33] [34] [35] : (a) case series and retrospective cohorts [4, [17] [18] [19] , (b) randomized controlled trials of specifi c treatments for IPF [3] , (c) autopsy reviews [8, 16, 33] , and (d) retrospective reviews of ICU admissions [28, 29, 31, 32] . Discrepancies in reported frequen cies should be attributed to the diffi culty in strictly respecting the defi nition criteria especially concerning symptom duration (less than 4 weeks) and the defi nite exclusion of infection [3, 6, 36] . IPF exacerbations do not appear to be linked to disease duration, functional derange ment, age, gender, or smoking history [4, 29] , although further studies are necessary to confi rm early development as well as lack of association with immunosuppression [37] . Exacerbation mortality approaches 100%, questioning the need for ICU admission [2] [3] [4] [5] [6] 8, 14, 16, 19, 28, 29, [31] [32] [33] [34] .