Fig. 4

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