Fig. 3

The time–response relationship association between duration of prone session, PaCO₂, PaO₂, PEEP and 28-day mortality. Cubic spline curves are shown as a solid line, with the shaded area representing the 95% CI. A The time–response relationship association between duration of prone session and 28-day mortality; B The time–response relationship association between PaCO₂ and 28-day mortality; C The time–response relationship association between PaO₂ and 28-day mortality; D The time–response relationship association between PEEP and 28-day mortality. PEEP positive end-expiratory pressure, HR hazard ratio, CI confidence interval