APRV outcomes

Proponents of APRV emphasize that the high mean airway pressure and long inspiratory time increase alveolar recruitment, including dependent alveoli, and thereby improve oxygenation in patients with ARDS. Several features, however, violate principles of conventional lung-protective ventilation. Whereas the equivalent of the plateau pressure—Phigh—is typically set at or below 30 cm H2O, the driving pressure (Phigh-Plow) often exceeds 15 to 20 cm H2O. Additionally, in published APRV trials, tidal volume often exceeded 6 mL/kg predicted body weight. Further, the very brief Tlow results in incomplete exhalation and autoPEEP are uniformly present.

Demonstration of clinical outcome benefit of APRV has been hindered by a paucity of multicenter, randomized, controlled trials (RCTs) and by wide variability in APRV ventilator settings (particularly Plow and Tlow). Two 2021 meta-analyses were inconsistent in their conclusions about potential clinical benefits of APRV, but better oxygenation, shorter ICU length of stay, and lower 28-day mortality were reported in one or the other meta-analysis. Oddly, these meta-analyses analyzed somewhat different published studies (perhaps explaining the differences in their results), and both raised concerns about potential bias and inconsistent comparison with modern low tidal volume ventilation. A 2018 RCT of children with ARDS demonstrated a trend for higher mortality with APRV compared with conventional ventilatory management. Collectively, these results highlight the need for additional high-quality, adequately powered RCTs.1234567

Footnotes

  1. SEEK Questionnaires ↩

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  7. Zhou Y, Jin X, Lv Y, et al. Early application of airway pressure release ventilation may reduce the duration of mechanical ventilation in acute respiratory distress syndrome. Intensive Care Med. 2017;43(11):1648-1659. PubMed ↩