Clinical Studies Assessing NIV in ARDS

NIV has been chiefly evaluated in two indications in ALI/ARDS: first, as an alternative to invasive mechanical ventilation in patients with acute hypoxemic respiratory failure meeting criteria for intubation, and second, as a mean of avoiding intubation in patients with acute respiratory failure who do not meet criteria for invasive mechanical ventilation.

NIV as an Alternative to Invasive Mechanical Ventilation

This indication has been investigated in the seminal study by Antonelli et al. [28]. The authors compared conventional mechanical ventilation and NIV (pressure support plus positive end-expiratory pressure). They reported similar improvement in gas exchange with the two techniques. Notably, only 31% of patients (10/32) treated with NIV required tracheal intubation. Furthermore, authors found that 9 of the 10 patients who were intubated after failing the NIV attempt died in the ICU (90%), whereas only 15 of 32 (47%) who had been intubated without a previous NIV trial died [28]. Complications were decreased in the group using NIV, and mortality tended to be lower with NIV. The study design differs from other NIV studies. The more conventional design has been to randomize patients to NIV or conventional medical therapy as a way to prevent the need for intubation, intubation being an outcome variable. When patients in the control group are intubated per study protocol, it prompts the question of whether intubation was indeed mandatory in all patients in the control group. Furthermore, the study of Antonelli et al. enrolled patients with a variety of diagnoses, making it difficult to apply the study findings to individual patients presenting with acute hypoxemic respiratory failure. Finally, this was a small sample size of patients coming from a single-center study. This kind of protocol has never been replicated. Therefore, the role of NIV with acute hypoxemic respiratory failure as an alternative to intubation remains ambiguous.