Reliability of the nitrogen washin-washout technique to assess end-expiratory lung volume at variable PEEP and tidal volumes

Intensive Care Medicine Experimental

Table 3 Diagnostic performance of EELV _WI-WO to detect variations in ELLV _CT at different thresholds

ΔEELV_CTthreshold for AUC computation (mL)	AUC (CI 95%)	Optimal ΔEELV_WI-WOcut-off (mL)	Se	Sp	PPV	NPV	PLR	NLR	Youden index
100	0.58 (0.50 to 0.66)	42	0.84	0.33	0.57	0.66	1.25	0.48	0.17
150	0.73 (0.64 to 0.81)	166	0.65	0.75	0.46	0.87	2.61	0.47	0.40
200	0.79 (0.70 to 0.89)	166	0.80	0.75	0.42	0.94	3.26	0.27	0.55
250	0.87 (0.79 to 0.94)	169	0.90	0.77	0.41	0.97	3.89	0.13	0.67
300	0.89 (0.83 to 0.95)	169	0.93	0.77	0.41	0.98	4.05	0.09	0.70

AUC, area under receiver operating characteristic curve; CI 95%, 95% confidence interval; ΔEELV_CT, absolute change in end-expiratory lung volume assessed by computed tomography between consecutive time points; ΔEELV_WI-WO, absolute change in end-expiratory lung volume assessed with the nitrogen washin-washout technique between consecutive time points; NLR, negative likehood ratio; NPV, negative predictive value; PLR, positive likehood ratio; PPV, positive predictive value; Se, sensitivity, Sp, specificity.