Noninvasive ventilation in critically ill very old patients with pneumonia: A multicenter retrospective cohort study

Background Very old patients (>= 80 years-old, VOP) are increasingly admitted to intensive care units (ICUs). Community-acquired pneumonia (CAP) is a common reason for admission and the best strategy of support for respiratory failure in this scenario is not fully known. We evaluated whether noninvasive ventilation (NIV) would be beneficial compared to invasive mechanical ventilation (IMV) regarding hospital mortality. Methods Multicenter cohort study of VOPs admitted with CAP in need of IMV or NIV to 11 Brazilian ICUs from 2009 through 2012. We used logistic regression models to evaluate the association between the initial ventilatory strategy (NIV vs. IMV) and hospital mortality adjusting for confounding factors. We evaluated effect modification with interaction terms in pre-specified sub-groups. Results Of 369 VOPs admitted for CAP with respiratory failure, 232 (63%) received NIV and 137 (37%) received IMV as initial ventilatory strategy. IMV patients were sicker at baseline (median SOFA 8 vs. 4). Hospital mortality was 114/232 (49%) for NIV and 90/137 (66%) for IMV. For the comparison NIV vs. IMV (reference), the crude odds ratio (OR) was 0.50 (95% CI, 0.33-0.78, p = 0.002). This association was largely confounded by antecedent characteristics and non-respiratory SOFA (adjOR = 0.70, 95% CI, 0.41-1.20, p = 0.196). The fully adjusted model, additionally including P(a)o(2)/F(i)o(2) ratio, pH and P(a)co(2), yielded an adjOR of 0.81 (95% CI, 0.46-1.41, p = 0.452). There was no strong evidence of effect modification among relevant subgroups, such as P(a)o(2)/F(i)o(2) ratio <= 150 (p = 0.30), acute respiratory acidosis (p = 0.42) and non-respiratory SOFA >= 4 (p = 0.53). Conclusions NIV was not associated with lower hospital mortality when compared to IMV in critically ill VOP admitted with CAP, but there was no strong signal of harm from its use. The main confounders of this association were both the severity of respiratory dysfunction and of extrarespiratory organ failures.