Abstract-Text (inkl. Referenzen und Bildunterschriften)

Background. In mechanically ventilated neurocritical care patients positive end-expiratory pressure (PEEP) has long been discussed as potentially detrimental for intracranial pressure (ICP). However, various studies failed to identify a relevant effect of PEEP on ICP and to date optimal ventilation strategy concerning airway pressure in brain-injured patients are not established. In this prospective physiological study, we focused on the relevance of different ventilation pressure settings on ICP.

Methods. We prospectively included 22 adult, intubated and mechanically ventilated neurocritical care patients with intraventricular ICP monitoring. Patients were only included with a stable ICP < 20mmHg over at least 72 hours and absence of acute lung injury such as pneumonia or adult respiratory distress syndrome (ARDS). Each patient passed three measurement cycles: at first (cycle 1; C1), PEEP and inspiration pressure (Pinsp) were increased simultaneously, second (C2), only PEEP was increased and third (C3), only Pinsp was increased. The pressure settings were continuously increased in steps of 2 mbar every 5 minutes starting at baseline (t0) until a maximum of +12 mbar (t12) was reached. We adjusted the ventilation to accomplish stable endtidal carbondioxide (etCO2) levels. ICP and hemodynamic Parameters at each ventilator setting were recorded. The local ethic committee approved the study under reference #5162R.

Results. In the C1 group, while increasing PEEP (from 6mbar at t0 to 18mbar at t12) and Pinsp (from 17mbar at t0 to 30mbar at t12), we recorded a continuous increase in ICP (5mmHg at t0 to 10mmHg at t12). In the C3 group with a non-dynamic PEEP fixed at median 6 mbar (range 5-10 mbar) and only gradual increase in Pinsp from (t0) 17 to (t12) we saw a stable ICP of median 4 mmHg (range 0 – 11mmHg). The difference in ICP for t0 and t2 was not significant, however with increasing difference in PEEP the difference in ICP became increasingly significant (t4 p=0.025; t6 p=0.024; t8, t10 and t12 p=0.003 respectively).

Conclusion. In this setting, a dynamically increased PEEP with increasing Pinsp increases ICP values as compared to fixed PEEP setting with increasing Pinsp.