Effectiveness and predictors of success of noninvasive ventilation during H1N1 pandemics: a multicenter study.

The use of non-invasive ventilation (NIV) in acute hypoxemic respiratory failure (AHRF) due to H1N1 virus infection is controversial. In this multicenter study we aimed to assess the efficacy of NIV in avoiding endotracheal intubation (ETI) and to identify predictors of success or failure. In this prospective multicenter study, 98 patients with new pulmonary infiltrate(s) sustained by H1N1 virus and a PaO2/FiO2<300 were eligible for study. 38/98 required immediate ETI, while the others received NIV as a first line therapy. 13/60 patients failed NIV and were intubated after 5.8+5.5 hours from enrolment. The remaining 47/60 patients were successfully ventilated with NIV. Hospital mortality was significantly higher in those patients who failed NIV vs those who succeeded (53.8% vs 2.1%; OR=0.52, p<0.001). ETI was associated with higher number of infectious complications, mainly sepsis and septic shock. The OR of having one of these events in the NIV failure group vs NIV success was 16.7, p<0.001. According to logistic regression model, a SAPS II >29 and a PaO2/FIO2R127 at admission and PaO2/FIO2R149 after 1 hr of NIV were independently associated with the need for ETI. The early application of NIV, with the aim to avoid invasive ventilation, during the H1N1 pandemics was associated with an overall success rate of 47/98 (48%). Patients presenting at admission with an high SAPS II score and a low PaO2/FiO2 ratio and/or unable to promptly correct gas exchange are at high risk of intubation and mortality.