Residual Pulse Morphology Visualization and Analysis in Pressure Signals

We describe a new method to determine whether there is additional information contained in the intracranial pulse morphology that cannot be explained by covariation with the mean intracranial pressure (ICP) alone. Our procedure calculates and displays the difference between the actual pulse morphology and the expected morphology given a predictor variable, such as the mean ICP. The display is intuitive and permits easy recognition of changes in morphology unaccounted for by the given predictor variable. This method can be applied to any signal that consists of a series of events that generate a consistent morphology that is correlated to other predictor variables. Our exploratory analysis of ICP signals revealed examples of changes in pulse morphology that were independent of mean ICP. This suggests the need for further work that examines the underlying physiology responsible for pulse morphology