Tracing best PEEP by applying PEEP as a RAMP
Intensive Care Medicine , Volume 24 - Issue 8 p. 821- 828
Objective: The aim of this study was to show the feasibility of a slow continuously increasing level of positive end-expiratory pressure (PEEP) (ramp manoeuvre) in selecting best PEEP and to evaluate whether best PEEP, as definded by maximal oxygen transport, coincides with best systemic arterial oxygenation or best compliance. Design: In 11 anaesthetized piglets, PEEP was increased between 0 cmH 2O (zero end-expiratory pressure; ZEEP) and 15 cmH 2O (PEEP 15) with a constant rate of 0.67 cmH 2O min -1. This ramp manoeuvre was performed both under normal conditions and after induction of an experimental lung oedema. During the ramp manoeuvre, haemodynamic and pulmonary variables were monitored almost continuously. Results: During the rise in PEEP, cardiac output declined in a non-linear way. In the series with normal conditions, best PEEP was always found at ZEEP. In the series with experimental lung oedema, best PEEP, as defined by maximum oxygen transport, was found at PEEP 1-6, as defined by maximal compliance, at PEEP 7.5 and by maximal arterial oxygen tension (PaO 2) at PEEP 10-14. Conclusions: Best PEEP according to oxygen transport is lower than best PEEP according to compliance and PaO 2; the use of PEEP as a ramp might prevent unnecessarily high levels of PEEP.