Pleural effusion during weaning from mechanical ventilation: a prospective observational multicenter study

Annals of Intensive Care

Table 4 Univariate and multivariable logistic regression of factors associated with weaning failure (n = 246)

Variables	Missing values, n (%)	Absolute standardized differences	Odd ratio (95% confidence interval), p value by logistic regression
Variables	Missing values, n (%)	Absolute standardized differences	Univariate	Multivariable
Age (per year)	0	47	1.03 (1.01–1.05), p = 0.01	1.02 (0.997–1.05), p = 0.08
Body mass index (per kg/m²)	6 (2%)	32	1.06 (1.01–1.11), p = 0.02	I/NR
COPD (yes vs. no)	0	48	3.0 (1.6–5.8), p = 0.001	2.2 (1.02–4.7), p = 0.045
Cardiac disease (yes vs. no)	0	37	2.2 (1.2–4.0), p = 0.01	I/NR
Left ventricle ejection fraction at cardiac ultrasound (%)	44 (18%)	27	0.98 (0.96–1.0), p = 0.09	NI
Supra–ventricular arrhythmias (yes vs. no)	0	26	1.9 (1.01–3.6), p = 0.046	NI
Septic shock (yes vs. no)	0	37	2.1 (1.2–3.7), p = 0.01	I/NR
Fluid balance between ICU admission and first SBT (per L)	15 (6%)	44	1.07 (1.03–1.12), p = 0.002	NI
Acute respiratory failure as cause of intubation (yes vs. no)	0	55	3.0 (1.7–5.2), p < 0.001	NI
PaO₂/FiO₂ ratio (per mmHg)	3 (1%)	58	0.994 (0.991–0.997), p < 0.001	0.996 (0.993–1.0), p = 0.03
Duration of MV before the first SBT (per day)	0	57	1.11 (1.06–1.17), p < 0.001	1.11 (1.05–1.17), p < 0.001
ARDS before the first SBT (yes vs. no)	0	49	3.0 (1.6–5.7), p < 0.001	NI
Neuromuscular blockade before the first SBT (yes vs. no)	0	54	3.5 (1.9–6.6), p < 0.001	NI
VAP before the first SBT (yes vs. no)	0	33	2.6 (1.2–5.4), p = 0.01	NI
Moderate-to-large pleural effusion (yes vs. no)	0	58	3.2 (1.8–5.7), p < 0.001	3.0 (1.5–5.8), p = 0.001

SAPS II simplified acute physiology score, COPD chronic obstructive pulmonary disease, ARDS acute respiratory distress syndrome, VAP ventilator-associated pneumonia, SBT spontaneous breathing trial, NI not included, I/NR included, but not retained by the final model
Among related univariate factors, only the most statistically robust (yet clinically relevant) was entered into the regression model in order to minimize the effect of colinearity. The selection process was guided by consistency (less than 5% missing values) and maximal imbalances between groups (as estimated by absolute standardized differences), as follows: cardiac disease was selected among supra-ventricular arrhythmias, left ventricle ejection fraction and cardiac disease; septic shock was selected among fluid balance between ICU admission and first SBT and septic shock; PaO₂/FiO₂ ratio was selected among acute respiratory failure as cause of intubation and PaO₂/FiO₂ ratio; duration of MV before the first SBT was selected among neuromuscular blockade, duration of MV before the first SBT, VAP, and ARDS. The multivariable model showed a good calibration as assessed by the Hosmer and Lemeshow goodness-of-fit test [χ² (8 df) = 6.8, p = 0.56] and a fair discrimination as assessed by the receiver operating characteristics curve [area under the curve of 0.76 (0.69–0.82), p < 0.001]