Fig. 2

Kaplan–Meier curves of mortality for the three study groups. Differences in mortality between rapidly improving acute respiratory distress (ARDS) group, intermediate group and persistent severe ARDS group were assessed using the log-rank test. There was no statistically significant difference between rapidly improving ARDS group and intermediate group, while there were statistically significant differences between persistent severe ARDS group and rapidly improving ARDS group (p = 0.018) or intermediate group (p < 0.001). Patients discharged from the intensive care unit with unassisted breathing before 28 days considered to be alive at 28 days following intubation