Fig. 7.

Individual PRx responses to refractory intracranial hypertension expressed relative to changes in ICP (left) and CPP (right) (n = 24). While pressure reactivity index increased with increasing ICP in each patient, in some patients, PRx was disturbed (above > 0.25) even at relatively normal ICP (below 25 mm Hg). PRx plotted against CPP revealed a partial ‘U-shaped’ curve in most patients, as previously described. PRx is well maintained until CPP drops below 70 mm Hg, below which PRx deteriorates. PRx pressure reactivity; ICP intracranial pressure; CPP cerebral perfusion pressure