PEEP Setting Strategy

Conventional PEEP setting often relies on oxygenation, but oxygenation is not a reliable indicator of recruitment. The EXPRESS trial was the only trial comparing PEEP strategies with potentially positive results; it used mechanics-based PEEP titration rather than oxygenation alone and showed benefit on duration of ventilation. Prior randomised trials comparing PEEP levels failed to identify which patients had recruitable lungs, which may explain why high-PEEP benefit could not be separated from harm. PEEP can be beneficial by preventing atelectrauma and promoting recruitment, but harmful in non-recruitable lungs by promoting overdistension and haemodynamic compromise. When airway closure is present, measured plateau and driving pressures reflect pressure in closed airways rather than alveolar pressure, impairing their interpretation. Complete airway closure above 5 cm H2O is present in 30% to 40% of ARDS patients.