Table 2.

Multivariable logistic regression analysis on the association between length of NIV application and in-hospital mortality.

	OR of in-hospital mortality (95% CI)	p value*
Age (years)	1.18 (1.04–1.33)	< 0.01
Charlson comorbidity index	0.96 (0.70–1.31)	0.80
SOFA score at ICU admission	1.19 (0.86–1.63)	0.29
PaO2/FiO2 before IMV	1.01(0.95–1.03)	0.55
Length of NIV before ICU admission (days)	2.30 (1.06–4.98)	0.03
Length of NIV after ICU admission (days)	1.16 (0.77–1.73)	0.48
Overall length of NIV (days)	1.12(0.77–1.64)	0.55

Data are expressed as Odds ratios (OR) and 95% Confidence Interval (CI).

Bold values are statistically significant.

*: Stepwise regression models, which combine forward and backward selection methods in an iterative procedure (with a significance level of 0.05 both for entry and retention) to select predictors in the final multivariable model. Independent variables used in the stepwise approach were selected considering their clinical relevance.

SOFA: sequential organ failure assessment; ICU: intensive care unit; PaO₂/FiO₂: ratio between partial pressure of arterial oxygen and fraction of inspired oxygen; NIV: non-invasive ventilation; IMV: invasive mechanical ventilation.