Positive end-expiratory pressure, prone positioning, and activated protein C: a critical review of meta-analyses

The results of meta-analyses on the effectiveness of high positive end-expiratory pressure (PEEP) and prone positioning in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are not consistent. In addition, the meta-analyses on the activated protein C in patients with sepsis combine trials with discordant results. Therefore, the aim of this paper was to give a critical review of these meta-analyses. All relevant meta-analyses were identified by a computerized search of PubMed using combinations of the following terms: acute lung injury, acute respiratory distress syndrome, positive end-expiratory pressure, mechanical ventilation, prone position, drotrecogin, activated protein C, sepsis, and septic patients. A high level of PEEP and prone ventilation was shown to reduce the mortality in patients with severe acute hypoxemic respiratory failure. Although the evidence for the efficacy of activated protein C is not conclusive, it should be considered in patients that are at a high risk for death without any contraindications related to bleeding risk. Meta-analysis models can be very useful for clinical decisions if they include all of the similar papers on a medical topic and are correct from the methodological point of view; however, these results must be checked by a careful and well-informed reader.