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Setting PEEP has to be one of the most confusing things I do. There are some pretty clear therapeutic benefits to PEEP - improved oxygenation and improved cardiac performance to name just 2 - but there can be some nasty complications too. Patient dyscomfort, barotrauma including pneumothorax, impaired cardiac output and increased intracerebral pressure are all potential complications. Add to that the heterogenous nature of pulmonary disease, where individual lung units may differ in their "ideal PEEP", and setting PEEP becomes an extremely complex balancing act. So how to set PEEP? Various techniques have been described. Some use the lower inflection point of the dynamic Pressure-Volume loop, arguing that this represents the point at which de-recruitment occurs. Others use improvements in arterial oxygenation, or better still, oxygen delivery, titrating upwards until no further benefit is seen. Some groups follow perform a recruitment manoeuvre and reduce PEEP until evidence of de-recruitment occurs, while others increase PEEP until no further improvements in compliance occur. Others still use tables, as described in the famous ARDS-net trials, titrating PEEP depending on FiO2 required. Each though has its problems. Recently a meta-analysis attempted to review the available literature, reviewing 3 major trials totaling over 2200 patients. They found benefit only in the sickest of patients (those with ARDS), while the incidence of complications did not differ significantly. So until more information comes along, perhaps the best approach remains to "suck it and see". Or is it? Reference : Briel M, Meade M, Mercat A, et al. Higher vs Lower Positive End-Expiratory Pressure in Patients With Acute Lung Injury and Acute Respiratory Distress Syndrome: Systematic Review and Meta-analysis. JAMA.2010; 303: 865-873.