COHmax: an algorithm to maximise coherence in estimates of dynamic cerebral autoregulation.OBJECTIVE
 A new algorithm (COHmax) is proposed to increase values of coherence by means of the automated, selective removal of sub-segments of data.


 COHmax has the potential to improve the yield of TFA estimates of dCA parameters, without introducing a bias or deterioration of their ability to detect impairment of autoregulation. 
COHmax
The reliability of dynamic cerebral autoregulation (dCA) parameters, obtained with transfer function analysis (TFA) of spontaneous fluctuations in arterial blood pressure (BP), require statistically significant values of the coherence function.  TFA was performed with sub-segments of data of duration (SEGD) 100 s, 50 s or 25 s and the autoregulation index (ARI) was obtained from the CBFV response to a step change in BP.  COHmax has the potential to improve the yield of TFA estimates of dCA parameters, without introducing a bias or deterioration of their ability to detect impairment of autoregulation. 
TFA
BP (Finapres), cerebral blood flow velocity (CBFV, transcranial Doppler), end-tidal CO2 (EtCO2, capnography) and heart rate (ECG) were recorded continuously during 5 min in each condition. 
Finapres
BP (Finapres), cerebral blood flow velocity (CBFV, transcranial Doppler), end-tidal CO2 (EtCO2, capnography) and heart rate (ECG) were recorded continuously during 5 min in each condition. 
transcranial Doppler
BP (Finapres), cerebral blood flow velocity (CBFV, transcranial Doppler), end-tidal CO2 (EtCO2, capnography) and heart rate (ECG) were recorded continuously during 5 min in each condition. 
capnography
BP (Finapres), cerebral blood flow velocity (CBFV, transcranial Doppler), end-tidal CO2 (EtCO2, capnography) and heart rate (ECG) were recorded continuously during 5 min in each condition. 
ECG