When NIV Should Not Be Used in Acute Hypoxemic Respiratory Failure

Based on the high intubation rate reported above, it is important to know when NIV should not be applied in patients with acute hypoxemic respiratory failure. Most of the studies that reported the experience of using NIV in acute hypoxemic respiratory failure have proposed predictors of NIV failure. In 2001, Antonelli et al. investigated in a prospective multicenter cohort study factors involved in NIV failure [41]. In a heterogeneous population, the overall efficacy of NIV in avoiding intubation (70%) contrasted with the high rate of failure observed in 86 patients fulfilling the diagnosis of ARDS (51%). The intubation rate was similar among patients with ARDS of pulmonary versus extrapulmonary origin, but sepsis on admission was associated, among other variables, with NIV failure. In a large prospective observational study of NIV in 147 ARDS patients in experienced centers (NIV failure rate around 50%), a high Simplified Acute Physiology Score (SAPS) II and PaO₂/ FiO₂ < 175 mmHg 1 h after initiation of NIV were independently associated with NIV failure [42]. Rana et al. [38] found that NIV success was significantly correlated with low severity scores (Acute Physiology and Chronic Health Evaluation III or Sequential Organ Failure Assessment), with high PaO₂/FiO₂ (147 vs. 112), and with less pronounced acidosis than patients with NIV failure. Last, Thille et al. found that shock, active cancer, low level of consciousness, and mild/severe ARDS were independently associated with NIV failure [39].