[The significance of point-inflection at static pressure-volume curve in optimal PEEP at early stage of ARDS in sheep].
OBJECTIVE
To study the optimal level of PEEP at early stage of ARDS.


METHODS
The parameters of hemodynamics, lung mechanics, and gas exchange were compared at different levels of PEEP, including maximal static compliance PEEP, point-inflection PEEP, 3 cmH2O higher or lower than point-inflection PEEP, and zero end-expiratory pressure.


RESULTS
Point-inflection PEEP (6.8 +/- 1.4 cmH2O) was significantly lower than maximal static compliance PEEP (9.3 +/- 1.4 cmH2O), P < 0.01. The hemodynamic parameters were not significantly different in point-inflection PEEP compared with 0cmH2O-PEEP (P > 0.05), but oxygenation index (PaO2/FiO2) and lung mechanics (static compliance and airway resistance) were improved significantly at point-inflection PEEP (P < 0.01). At maximal static compliance PEEP or 3 cmH2O higher than point-inflection PEEP, the hemodynamic parameters and PaO2/FiO2 were not different from those at point-inflection PEEP (P > 0.05). The pulmonary vascular resistance index (PVRI) was significantly higher (P < 0.05) and the mean airway pressure and peak inspiratory pressure increased significantly (P < 0.01).


CONCLUSIONS
In the treatment of early ARDS, the PEEP needed may be lower than the "optimal PEEP" determined by obtaining the maximal static compliance. The application of point-inflection PEEP determined at inspiratory static pressure-volume curve was appropriate as the best PEEP.
Zhang
H
H
Department of Critical Care Medicine, Peking Union Medical College Hospital, Beijing.
Ma
S
S
Chao
Y
Y
D000818:Animals; D006439:Hemodynamics; D011175:Positive-Pressure Respiration; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*; D012756:Sheep