Article

Two computerized methods used to analyze intracranial pressure B waves: comparison with traditional visual interpretation.

Department of Biomedical Engineering and Informatics, University of Umeå, Sweden.
Journal of Neurosurgery (impact factor: 2.96). 04/2001; 94(3):392-6. DOI:10.3171/jns.2001.94.3.0392 pp.392-6
Source: PubMed

ABSTRACT Slow and rhythmic oscillations in intracranial pressure (ICP), also known as B waves, have been claimed to be one of the best preoperative predictive factors in idiopathic adult hydrocephalus syndrome (IAHS). Definitions of B waves vary widely, and previously reported results must be treated with caution. The aims of the present study were to develop a definition of B waves, to develop a method to estimate the B-wave content in an ICP recording by using computer algorithms, and to validate these procedures by comparison with the traditional visual interpretation.
In eight patients with IAHS, ICP was continuously monitored for approximately 20 hours. The ICP B-wave activity as a percentage of total monitoring time (B%) was estimated by using visual estimation according to the definition given by Lundberg, and also by using two computer algorithms (Methods I and II). In Method I each individual wave was classified as a B wave or not, whereas Method II was used to estimate the B-wave content by evaluating the B-wave power in 10-minute blocks of ICP recordings.
The two computerized algorithms produced similar results. However, with the amplitude set to 1 mm Hg, Method I yielded the highest correlation with the visual analysis (r = 0.74). At least 5 hours of monitoring time was needed for an acceptable approximation of the B% in an overnight ICP recording. The advantages of using modern technology in the analysis of B-wave content of ICP are obvious and these methods should be used in future studies.

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    Article: Real-time estimation of cerebrospinal fluid system parameters via oscillating pressure infusion.
    Kennet Andersson, Ian R Manchester, Jan Malm, Anders Eklund
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    ABSTRACT: Hydrocephalus is related to a disturbed cerebrospinal fluid (CSF) system. For diagnosis, lumbar infusion test are performed to estimate outflow conductance, C (out), and pressure volume index, PVI, of the CSF system. Infusion patterns and analysis methods used in current clinical practice are not optimized. Minimizing the investigation time with sufficient accuracy is of major clinical relevance. The aim of this study was to propose and experimentally evaluate a new method, the oscillating pressure infusion (OPI). The non-linear model of the CSF system was transformed into a linear time invariant system. Using an oscillating pressure pattern and linear system identification methods, C (out) and PVI with confidence intervals, were estimated in real-time. Forty-two OPI and constant pressure infusion (CPI) investigations were performed on an experimental CSF system, designed with PVI = 25.5 ml and variable C (out). The ARX model robustly estimated C (out) (mean C (out,OPI) - C (out,CPI) = 0.08 μl/(s kPa), n = 42, P = 0.68). The Box-Jenkins model proved most reliable for PVI (23.7 ± 2.0 ml, n = 42). The OPI method, with its oscillating pressure pattern and new parameter estimation methods, efficiently estimated C (out) and PVI as well as their confidence intervals in real-time. The results from this experimental study show potential for the OPI method and supports further evaluation in a clinical setting.
    Medical & Biological Engineering 11/2010; 48(11):1123-31. · 1.76 Impact Factor
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Keywords

acceptable approximation
 
B wave
 
B waves
 
B-wave content
 
B-wave power
 
computer algorithms
 
ICP B-wave activity
 
ICP recording
 
ICP recordings
 
idiopathic adult hydrocephalus syndrome
 
individual wave
 
intracranial pressure
 
Method II
 
modern technology
 
monitoring time
 
preoperative predictive factors
 
total monitoring time
 
traditional visual interpretation
 
two computerized algorithms
 
visual estimation