ICU · Respiratory / ventilation

PEEP — Physiology, Setting & Optimisation

Also known as Positive end-expiratory pressure · PEEP · Extrinsic PEEP · Intrinsic PEEP · Auto-PEEP · Best PEEP · Alveolar recruitment · Recruitment manoeuvre · Atelectrauma · Driving pressure

Positive end-expiratory pressure (PEEP) is positive pressure maintained in the airways above atmospheric at end-expiration. It recruits collapsed alveoli, raises functional residual capacity, improves oxygenation by reducing shunt, and prevents the cyclic collapse-reopening of atelectrauma, which is central to lung-protective ventilation (the ARDSnet PEEP/FiO2 tables). Excessive PEEP reduces venous return and cardiac output, raises RV afterload, overdistends alveoli (volutrauma), and raises intracranial pressure. 'Best PEEP' maximises oxygenation and compliance without haemodynamic compromise. Intrinsic (auto-) PEEP from incomplete expiration in COPD and asthma causes hyperinflation; applying external PEEP at about 75-80 per cent of auto-PEEP counteracts the inspiratory threshold load.