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Influence of Positive End-Expiratory Pressure Ventilation on Cerebral Perfusion and Cardiac Hemodynamics

Roland Backhaus, Elisabeth Torka, Michael Ertl, Lukas Kirzinger, Andrea Wagner, Dobri Baldaranov, Felix Schlachetzki and Kornelius Fuchs

Objective: Positive end-expiratory pressure (PEEP) ventilation is used to prevent alveolar collapse and improve oxygenation. PEEP ventilation hinders venous backflow to the right atrium as well as venous outflow from the brain including the spinal cord. This may have an effect on cardiac output (CO) and could result in an elevation in intracranial pressure (ICP) — an important cause of secondary brain injury. The aim of this study was to investigate the effect of moderate changes in PEEP values on hemodynamics and cerebral perfusion in neurological patients experiencing respiratory failure.

Methods: The study focused on 7 patients in a neurological intensive care unit who suffered from respiratory failure. Cerebral blood flow velocity was measured using transcranial color-coded duplex sonography (TCCS) while moderate changes in PEEP levels (10 cm, 7 cm or 5 cm H2O) were made to investigate cerebral arterial blood flow velocity, third ventricular diameter, and midline shift. Simultaneously, cardiac output was measured using a minimally invasive hemodynamic monitoring system (Vigileo® or PiCCO®).

Results: Rising PEEPs resulted in a non-significant trend toward increased brain volume, as shown by a mild linear regression of changes in third ventricular diameter. However, no significant changes in cerebral blood flow parameters or hemodynamics values such as blood pressure, heart frequency or cardiac output, were noticed.

Conclusion: Low to moderate changes in PEEP appear to increase brain volume slightly, but cerebral autoregulatory compensatory mechanisms are sufficient to stabilize cerebral perfusion pressure and intravasal volume status. The effects of these changes in PEEP may be challenging in patients with impaired cerebral autoregulation (for example, in patients after subarachnoid hemorrhage or severe brain trauma) as well as in patients requiring a high level of PEEP ventilation (that is, patients with acute respiratory distress syndrome). In such patients TCCS and cardiac hemodynamics monitoring are warranted.