Fig. 2

Visualization of the fractional polynomial regression with inverse-transformed PaO₂ (= 1/PaO₂); p-value = 0.060. Figure Description: The figure illustrates the relationship between arterial oxygen partial pressure (PaO₂) and adjusted predicted 28-day mortality. The shaded blue area represents the 95% confidence interval for the predicted mortality. At PaO₂ levels below 10 kPa, predicted 28-day mortality is high, indicating a greater risk of death. As PaO₂ increases, predicted mortality decreases rapidly, showing that even small improvements in oxygen levels can significantly reduce mortality risk. Beyond 20–30 kPa, further increases in PaO₂ result in only marginal decreases in mortality, suggesting diminishing returns at higher oxygen levels. Abbreviations aBGA, Arterial Blood Gas Analysis. *adjusted on age, ISS, AIS head, systolic blood pressure (with imputed values), and prehospital intubation