Alveolar fluid clearance in healthy pigs and influence of positive end-expiratory pressure.
BACKGROUND
The 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).


METHODS
Animals (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.


RESULTS
At 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.


CONCLUSIONS
In 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.
Department of Intensive Care Medicine, Virgen de las Nieves University Hospital, Fuerzas Armadas, Granada, Spain. mjgardel@telefonica.net
Manuel
M
García-Delgado
Angel
A
Touma-Fernández
Virginia
V
Chamorro-Marín
Antonio
A
Ruiz-Aguilar
Eduardo
E
Aguilar-Alonso
Enrique
E
Fernández-Mondéjar
D000818:Animals; D015633:Extravascular Lung Water / Q000378:metabolism*; D006439:Hemodynamics; D023421:Models, Animal; D011175:Positive-Pressure Respiration / Q000379:methods*; D011654:Pulmonary Edema / Q000628:therapy*; D013552:Swine; D016896:Treatment Outcome