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Table 4 Area under the curve (AUC) differences and summary of added value for the predictive variables to the model at days 1 and 2

From: Estimated dead space fraction and the ventilatory ratio are associated with mortality in early ARDS

VariableWith dead space estimationBase modelap-valueNRI (95% IC)IDI (95% IC)
Day 1
 VD/VT
  Harris–Benedict0.690.690.680.23 (0.09 to 0.36)0.001 (− 0.001 to 0.004)
  Penn State0.690.690.820.22 (0.09 to 0.36)0.002 (− 0.001 to 0.005)
  Direct0.690.690.740.15 (− 0.17 to 0.30)0.002 (− 0.001 to 0.006)
 VR0.690.690.470.10 (− 0.03 to 0.24)0.002 (− 0.001 to 0.006)
Day 2
 VD/VT
  Harris–Benedict0.720.69< 0.010.44 (0.30 to 0.57)4.36 (2.90 to 5.80)
  Penn State0.720.69< 0.010.40 (0.25 to 0.52)4.46 (3.02 to 5.91)
  Direct0.720.69< 0.010.47 (0.33 to 0.60)4.54 (3.07 to 6.01)
 VR0.720.69< 0.010.45 (0.32 to 0.60)4.51 (3.04 to 6.00)
  1. VD/VT estimated dead space fraction, VR ventilatory ratio, NRI net reclassification improvement, IDI integrated discrimination improvement
  2. aBase model includes APACHE IV, PEEP, PaO2/FiO2, driving pressure and compliance of the respiratory system