Intrathoracic positive pressure may lead to a change hemodynamics, with repercussions for the intracranial compartment, thereby altering intracranial pressure (ICP) and cerebral perfusion pressure (CPP). This effect may become more intense when using high positive end expiratory pressure (PEEP) values. The aim of the present study was to measure the impact of different PEEP values on ICP, CPP and mean arterial pressure (MAP). MAP, whereas high PEEP values increase ICP, although without clinical relevance.

This study is a prospective clinical trial, developed in the neurological intensive care unit approved by the ethics committee and research in humans. The charge of each patient had information about the study through the completion of informed consent and signed him when he agreed. Were the following inclusion criteria: adult patients with acute CVA and presence of ventricular drainage catheter for invasive monitoring of ICP and without intracranial hypertension. Were adopted as exclusion criteria: increased intracranial pressure, hemodynamic instability as a criterion of loss was used to expressions of interest in charge to leave. All patients completed the study. <br>All patients were from the surgical implantation of the ventricular catheter, arriving to the ICU intubated orally and manually ventilated with an Ambu bag. Were subjected to routine procedures: adjusting the mechanical ventilator (Inter5, Intermed, BR) during assisted controlled cycled pressure and facility to monitor vital signs. After thirty minutes of stable ICU patient in a supine position with head elevated 30 °, the protocol was initiated to assess the impact of PEEP on ICP. To perform the evaluation of lung mechanics ventilatory mode was changed to control volume with the following parameters: tidal volume (Vt) = 8ml/kg weight, peak flow (PF) = 6 x minute volume, fraction of inspired O2 (FiO2) = 40%, respiratory rate (RR) = 16 bpm, sensitivity = 1 cmH2O. The following variables were monitored: PIC, Blood Pressure (BP), heart rate (HR), peak pressure in the airways (pp.) and plateau pressure of the respiratory system (Ppl.), these values were monitored with PEEP = 5 cmH2O. <br>During the assessment protocol was changed to pressure control ventilation mode with the following values of ventilatory parameters: Pp = 30 cm H2O, inspiratory time = 1s; FiO2 = 40%, RR = 16 bpm; Sensitivity = 1 cmH2O. PEEP employed ranged from 0 to 14 cmH2O. To eliminate a possible physiological accommodation by the progressive increase of PEEP, the range of values was determined by drawing a sealed envelope for each patient, ranging from 2 to 2 cmH2O. At each value of PEEP the patient was ventilated for a period of five minutes to carry out monitoring of ICP, BP, HR, PPC and peripheral oxygen saturation (SpO2). The ICP monitoring catheter was kept closed for drainage and open for monitoring, since the arrival of the surgical block, was only open for drainage if there was an increase in ICP above 20 mmHg. <br>The monitoring was carried out using the multiparameter monitor (Siemens 7000). For ICP monitoring the ventricular catheter was connected to a pressure transducer and this monitor. <br>After the parameters evaluated with seven different PEEP values, the ventilatory mode was changed again to control volume again to evaluate pulmonary mechanics with the same initial parameters.

Inclusion Criteria:

• adult patients with acute CVA
• presence of ventricular drainage catheter for invasive monitoring of ICP
• without intracranial hypertension.

Exclusion Criteria:

• intracranial hypertension
• hemodynamic instability.