A system device and method are presented for determining if cerebral blood flow autoregulation functionality has been compromised in a patient. The system includes sensors for detecting and measuring at least two physiological parameters such as oxygenation and blood pressure. The system analyzes these measurements and presents them as waveforms. Episodes of interest in each waveform are determined and compared. Any time lag between the occurrence of episodes of interest in each waveform is established and accounted for. Where there is correspondence between episodes of interest in each waveform then impairment of cerebral blood flow autoregulation is likely.