Inter-Subject Correlation Exists Between Morphological Metrics of Cerebral Blood Flow Velocity and Intracranial Pressure Pulses

Abstract

The prototypical intracranial pressure (ICP) pulse morphology has been well known to be triphasic. Several studies suggest that the morphology of ICP pulse reflects the physiological and pathophysiological conditions of the intracranial dynamics. Recently, there has been a renaissance of studying ICP pulse using new ICP signal processing technologies in various clinical contexts. Cerebral blood flow velocity (CBFV) pulse is another important pulsatile signal originated from the complex circulatory systems of cerebral blood flow. However, CBFV pulse morphology has not been well studied mainly due to the noise level and lack of signal processing techniques. Our group recently developed a technique called the morphological clustering and analysis of intracranial pressure that can extract a comprehensive set of pulse morphological metrics. We extend this algorithm to extract various morphological metrics from ICP and CBFV pulses that were simultaneously recorded from 47 brain injury patients and investigate the mutual correlation between those metrics utilizing the robust percentage bend correlation analysis. Our results show that CBFV pulses are also triphasic as ICP pulses and 15.2% of 128 pulse morphological metrics extracted from ICP and CBFV pulses are highly correlated (P < 0.01) in an inter-subject fashion. In addition, mean ICP does not correlate (P = 0.45) with the pulsatility index of CBFV pulses but correlates (P < 0.05) with several novel CBFV pulse morphological metrics such as the time interval between the onset of CBFV pulses and ECG QRS peak. Our results suggest that characterizing CBFV pulse morphology is clinically important because it may offer a potential noninvasive alternative to assess various aspects of ICP such as mean ICP.