Predictors of failure of noninvasive ventilation in patients with severe community-acquired pneumonia

Purpose: The study aimed to investigate cardiorespiratory parameters potentially predictive of failure of noninvasive ventilation (NIV) in severe community-acquired pneumonia (CAP). Patients and Methods: Sixty-four consecutive patients with severe CAP entered the study and underwent NIV with a helmet. Arterial blood gases, PaO2/FIO2, and oxygenation index (OI; mean airway pressure × FIO2 × 100/PaO2) were determined before and after a 1-hour trial of NIV. Results: Noninvasive ventilation succeeded in 28 patients (43%) and failed in 36 patients (56%). Patients who avoided intubation had significantly (P b .05) shorter stays in ICU and lower rates of mortality in ICU and in hospital. Patients who failed NIV had higher Simplified Acute Physiology Score II at ICU admission (33 ± 11 versus 29 ± 9) and lower pH before NIV trial (7.37 versus 7.44). Furthermore, patients who required intubation failed to improve or worsened arterial blood gases during NIV trial and, by the end of the trial, had lower (P b .05) pH (7.34 versus 7.44) and PaO2/FiO2 (177 versus 228) and higher OI (8.6 versus 5.0) and respiratory rate (28 versus 23 breaths/min). In a multivariate analysis, post-NIV to pre-NIV deltas of PaO2/FiO2 and of OI were independent predictors of NIV failure, with OI delta being significantly more accurate. Conclusions: Noninvasive ventilation failed in approximately half patients with severe CAP. Posttrial to pretrial deltas of PaO2/FiO2 and OI may help to guide decision about endotracheal intubation.