[Brain function and artificial respiration]

Haemodynamic changes (cerebral perfusion pressure, cerebral blood flow) and variations of blood gases (especially paCO2) induced by mechanical ventilation, can influence cerebral function. The cerebral response to these changes is modified by the individual pathophysiology of the cranial contents. The cerebral mechanisms of adaptation allow a safe ventilation of a patient without cerebral disorders, provided ventilation is within normal clinical limits. In patients, however, whose mechanisms of adaption are impaired locally or globally, the pathophysiological situation may become grossly changed by variations in the ventilatory pattern. A therapeutical application of this interaction is controlled hyperventilation to lower intracranial pressure. On the other hand, changes in the ventilatory pattern (variation of PEEP-level, variation of minute volume, bronchial toilet) can impair cerebral function critically. As the individual reactions cannot be predicted in this group of patients, monitoring of haemodynamic parameters (MAP, CVP, CO), blood gases, intracranial pressure, and EEG is of utmost importance.