Fig. 3

Kaplan–Meier curves of hospital survival probability in the whole (non-matched) cohort (a) and in the propensity score-matched cohort (b). ARDS patients with no risk factor identified (red curve) exhibited a non-significantly different probability of mortality during hospital stay, as compared with those having one or more risk factor identified (blue curve) both in the whole (a, p = 0.13, by the log-rank test) and the matched cohort (b, p = 0.73 by the Cox proportional hazard model)