• Manuel García-Delgado, Angel Touma-Fernández, Virginia Chamorro-Marín, Antonio Ruiz-Aguilar, Eduardo Aguilar-Alonso, and Enrique Fernández-Mondéjar.
• Department of Intensive Care Medicine, Virgen de las Nieves University Hospital, Fuerzas Armadas, Granada, Spain. mjgardel@telefonica.net
• Crit Care. 2010 Jan 1; 14 (2): R36.

IntroductionThe objectives were to characterize alveolar fluid clearance (AFC) in pigs with normal lungs and to analyze the effect of immediate application of positive end-expiratory pressure (PEEP).MethodsAnimals (n = 25) were mechanically ventilated and divided into four groups: small edema (SE) group, producing pulmonary edema (PE) by intratracheal instillation of 4 ml/kg of saline solution; small edema with PEEP (SE + PEEP) group, same as previous but applying PEEP of 10 cmH2O; large edema (LE) group, producing PE by instillation of 10 ml/kg of saline solution; and large edema with PEEP (LE + PEEP) group, same as LE group but applying PEEP of 10 cmH2O. AFC was estimated from differences in extravascular lung water values obtained by transpulmonary thermodilution method.ResultsAt one hour, AFC was 19.4% in SE group and 18.0% in LE group. In the SE + PEEP group, the AFC rate was higher at one hour than at subsequent time points and higher than in the SE group (45.4% vs. 19.4% at one hour, P < 0.05). The AFC rate was also significantly higher in the LE + PEEP than in the LE group at three hours and four hours.ConclusionsIn this pig model, the AFC rate is around 20% at one hour and around 50% at four hours, regardless of the amount of edema, and is increased by the application of PEEP.

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