Assessment of Cerebral Hemodynamics in Traumatic Brain Injury
Abstract
We employ complex continuous wavelet transforms to develop a consistent mathematical framework capable of quantifying both cerebrospinal compensatory reserve and cerebrovascular pressure reactivity. The wavelet gain, defined as the frequency dependent ratio of time averaged wavelet coefficients of intracranial pressure (ICP) and arterial blood pressure (ABP) fluctuations, characterizes the dampening of spontaneous ABP oscillations. This gain is introduced as a novel measure of cerebrospinal compensatory reserve. For a group of 12 patients who died as a result of cerebral lesions (Glasgow Outcome Scale GOS =1) the average gain = 0.45 calculated at f=0.05 Hz significantly exceeds that of 17 patients with GOS=2: wavelet gain = 0.24 with p = 4 10 (exp -5) (Kruskal-Wallis test). We also study the dynamics of instantaneous phase difference delta phi(f) between the fluctuations of ABP and ICP. The time-averaged synchronization index = (sine delta lambda) squared + (cos delta lambda) squared, which depends upon frequency, yields information about the stability of the phase difference delta lambda and is used as a cerebrovascular pressure reactivity index. For both groups of patients the synchronization is strong. We hypothesize that in patients who died the impairment of cerebral autoregulation is followed by the breakdown of residual pressure reactivity. For example at f=0.05 Hz, synchronization index = 0.70 (GOS=1) and synchronization index = 0.58 (GOS=2). While these two synchronization levels are not statistically different (p=0.15) the corresponding average phase difference for GOS=1 is equal to 10 degrees in sharp contrast to the mean value of 44 degrees for patients with GOS=2 (p = 1 x 0.0001).
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 2006
- Accession Number
- ADA481674
Entities
People
- B. J. West
- D. Latka
- M. Latka
- Malgorzata Turalska
- W. Kolodziej