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 < .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 < .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.