Figure 3.

Sustained improvement in PaO₂/FiO₂ by days between intubation and proning initiation. Sustained improvement was defined as a ≥10% improvement in PaO₂/FiO₂ between pre-proning measurement and measurement 48 h after proning initiation. Patients were segmented by the timing of proning initiation relative to the timing of intubation. Error bars represent the S.E. of the mean. Statistical significance is given by the χ-squared contingency test with α = 0.05.