POSITIVE END-EXPIRATORY PRESSURE REDUCES INTRACRANIAL COMPLIANCE IN THE RABBIT

Acute respiratory distress syndrome is commonly encountered in head-in jured patients. Positive end expiratory pressure (PEEP) is useful in i mproving oxygenation. However, PEEP, by increasing intrathoracic press ure, decreases venous return, mean arterial pressure, and cardiac outp ut and increases jugular vein pressure. There is conflicting evidence in the literature as to the potential effect of PEEP on intracranial p ressure (ICP). The present study was undertaken to examine the effect of PEEP on ICP and intracranial compliance. Twelve male rabbits weighi ng 3.5-4.5 kg were used. The following parameters were monitored: arte rial blood pressure, ICP (intraparenchymal Camino device), PaCO2, and PaO2. A space-occupying lesion was produced by inflation of a double l umen pediatric Swan-Ganz catheter placed over the right parietal dura. The amount of fluid required to reach the point of exponential increa se of ICP was recorded at PEEP of 0 and 10 cm H2O. The mean volume nee ded to reach the deflection point of ICP was significantly lower when PEEP was 10 cm H2O compared to the value when PEEP was 0 cm H2O (685 /- 48 vs. 883.3 +/- 46 mu l, respectively; p < 0.01). The results of t he present study indicated that PEEP of 10 cm H2O decreases intracrani al compensatory reserves for maintaining ICP at normal levels in the p resence of an expanding intracranial mass.