Effect of mechanical ventilation in the prone position on clinical outcomes in patients with acute hypoxemic respiratory failure: a systematic review and meta-analysis

piratory failure may require mechanical ventilation to maintain oxygenation. Persistent hypoxemia may entail additional treatments, such as inhaled nitric oxide or high-frequency oscillation, but these treatments are not universally available. In contrast, ventilation in the prone position, first recommended in 1974, can be readily implemented in any intensive care unit (ICU), and clinicians should be familiar with its effects on patient outcomes. Improved ventilation-perfusion matching is the major physiologic effect of prone positioning for ventilation in patients with acute lung injury. In the supine position, the dependent dorsal lung regions (compared with nondependent regions) are atelectatic owing to decreased transpulmonary pressure and direct compression by the lungs, heart and abdominal contents (via pressure on a passive diaphragm). Gravity favours increased perfusion to these collapsed dorsal lung segments, which creates shunt conditions. In the prone position, lung compression is decreased, and chest-wall and lung mechanics create more uniform transpulmonary pressure. The previously atelectatic lung thus becomes aerated, Research