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

Annals of Intensive Care

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

Variable	With dead space estimation	Base model^a	p-value	NRI (95% IC)	IDI (95% IC)
Day 1
V_D/V_T
Harris–Benedict	0.69	0.69	0.68	0.23 (0.09 to 0.36)	0.001 (− 0.001 to 0.004)
Penn State	0.69	0.69	0.82	0.22 (0.09 to 0.36)	0.002 (− 0.001 to 0.005)
Direct	0.69	0.69	0.74	0.15 (− 0.17 to 0.30)	0.002 (− 0.001 to 0.006)
VR	0.69	0.69	0.47	0.10 (− 0.03 to 0.24)	0.002 (− 0.001 to 0.006)
Day 2
V_D/V_T
Harris–Benedict	0.72	0.69	< 0.01	0.44 (0.30 to 0.57)	4.36 (2.90 to 5.80)
Penn State	0.72	0.69	< 0.01	0.40 (0.25 to 0.52)	4.46 (3.02 to 5.91)
Direct	0.72	0.69	< 0.01	0.47 (0.33 to 0.60)	4.54 (3.07 to 6.01)
VR	0.72	0.69	< 0.01	0.45 (0.32 to 0.60)	4.51 (3.04 to 6.00)

V_D/V_T estimated dead space fraction, VR ventilatory ratio, NRI net reclassification improvement, IDI integrated discrimination improvement
^aBase model includes APACHE IV, PEEP, PaO₂/FiO₂, driving pressure and compliance of the respiratory system