NIV as a Prophylactic Ventilator Support

This indication has been tested in several studies (Table 15.1). Wysocki et al. randomized 41 patients with acute respiratory failure not related to chronic obstructive pulmonary disease [29]. Patients were randomly assigned to receive conventional therapy (oxygen and medications related to the cause of the respiratory distress (antibiotics, diuretics)) or conventional therapy plus NIV. In this study, respiratory distress was due to pneumonia in 16 patients (39%) but not necessarily associated with ARDS. Seven of these patients were randomly assigned to NIV, none was successful, and all required endotracheal intubation. By contrast, respiratory distress was not due to pneumonia in 25 other patients (61%), and 14 were randomly assigned to receive NIV; 8 were successfully ventilated with NIV (p = 0.04). In a larger study, Ferrer et al. randomized 105 patients with severe acute hypoxemic respiratory failure to receive, via oronasal mask, either NIV or high FiO2 [30]. The main causes were pneumonia and cardiogenic lung edema, but there were 15 patients with ARDS. Overall the study was very positive in favor of NIV, which prevented intubation, reduced the incidence of septic shock, and improved survival compared with high-concentration oxygen therapy. The efficacy of NIV was, however, poor in the ARDS subgroup (intubation rate 86%). This study strictly selected cooperative patients with no other organ dysfunction. Confalonieri et al. randomized 56 patients presenting with acute hypoxemic respiratory failure and community-acquired pneumonia (not ARDS) to receive either NIV or standard treatment [37]. The intubation rate was 21% versus 50% for the NIV group and standard group (p = 0.03), respectively. The main limitation of this study was the presence of COPD in many patients, driving the benefits of NIV.

The role of NIV in the treatment of ALI was assessed in critically ill patients with bilateral infiltrates of different origin in a study from the Mayo Clinic [38]. In this observational cohort study, Rana et al. prospectively assessed the outcomes of 54 consecutive patients. They found that 70% of the patients failed NIV. It was of notice that in patients who failed NIV, the observed mortality was higher than APACHE-predicted mortality (68% vs. 39%, p < 0.01). Among 113 patients receiving NIV for acute hypoxemic respiratory failure (82 with acute ARDS and 31

Table 15.1 Studies reporting the effect of noninvasive ventilation on acute hypoxemic respiratory failure in immunocompetent patients

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Table 15.1 (continued)

ALI acute lung injury. ARDS acute respiratory distress syndrome. ARF acute respiratory failure. AECOPD acute exacerbation of chronic obstructive pulmonary disease. RCT randomized controlled trial. AW nonin vasive ventilation. CPAP continuous positive airway pressure. IMV invasive mechanical ventilation. HFNC high-flow oxygen through nasal cannula. SAPS II simplified acute physiology score without), Thille et al. reported intubation rates significantly different between ARDS and non-ARDS patients (61% vs. 35%, p = 0.015) and according to clinical severity of ARDS: 31% in mild, 62% in moderate, and 84% in severe ARDS (p = 0.0016) [39].

More recently, Frat et al. randomized 310 patients presenting acute hypoxemic respiratory failure without hypercapnia to receive either high-flow oxygen therapy or standard oxygen therapy delivered through a face mask or NIV [36]. The intubation rate was similar between the three groups (38%, 47%, and 50%, respectively, for the high-flow oxygen group, the standard group, and the NIV group; p = 0.18). However, it is important to note that the hazard ratio for death at 90 days was 2.01 (95% confidence interval [CI], 1.01-3.99) with standard oxygen versus high-flow oxygen (p = 0.046) and 2.50 (95% CI, 1.31-4.78) with NIV versus high-flow oxygen (p=0.006). Finally, another monocentric study reported intriguing results [40]. In this prospective study, investigators randomized 83 hypoxemic patients after 8 h of NIV to receive NIV provided with a helmet or NIV with a facial mask (as it was previously provided) [40]. The study was stopped earlier for safety since the preestablished criteria for stoppage were met. Hence, the main primary endpoint, the intubation rate, was 61.5% in the face mask group and 18.2% in the helmet group (absolute difference, -43.3%; 95% CI, -62.4% to -24.3%; p< .001). The helmet group had a higher PEEP (8 vs. 5 cmH₂O), whereas the pressure support level was higher in the face mask group (11 vs. 8 cmH₂O). With helmet, the assessment of tidal volume is not possible; however, the results could be explained by more protective ventilation provided by the helmet. Since it was a monocentric study, further studies are mandatory to confirm these challenging results.