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

Object. Slow and rhythmic oscillations in intracranial pressure (ICP), also known as B waves, have been claimed to be one of the best preoperative pre dictive factors in idiopathic adult hydrocephalus syndrome (IAHS). Definiti ons 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 o f B waves, to develop a method to estimate the B-wave content in an ICP rec ording by using computer algorithms, and to validate these procedures by co mparison with the traditional visual interpretation. Methods. In eight patients with IAHS,ICP was continuously monitored for app roximately 20 hours. The ICP B-wave activity as a percentage of total monit oring time (B%) was estimated by using visual estimation according to the d efinition given by Lundberg, and also by using two computer algorithms (Met hods I and TI). In Method I each individual wave was classified as a B wave or not, whereas Method Il was used to estimate the B-wave content by evalu ating the B-wave power in 10-minute blocks of TCP recordings. Conclusions. The two computerized algorithms produced similar results. Howe ver, with the amplitude set to 1 mm Hg, Method I yielded the highest correl ation with the visual analysis (r = 0.74). At least 5 hours of monitoring t ime was needed for an acceptable approximation of the B % in an overnight I CP 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 futur e studies.