From top to bottom the traces are as follows. (i) Time marker at one minute intervals. (ii) The 90th centile, the mean and the 10th centile of the amplitude distribution (backwards smoothed). Maximum and minimum excursions in any 2 second epoch are written in full above and below the centiles. (iii) Muscle activity, 50uV pk to pk = 1 square of the graticule. (iv) percentage of weighted EEG activity per Hz in the beta, alpha, theta, and delta bands. (v) Percentage of very low frequency activity (below 1Hz ). (vi) Suppression band: the percentage time that the weighted EEG is below 1uV pk to pk. (vii) Electrode impedance in Kohms. (vii) Line: the amplitude pk to pk of mains interference, 50uV= 1 square of the graticule. (viii) A marker bar can also be written below Line.
Data are analysed from either of two pairs of electrodes, making channels A and B. The amplitude distribution may be displayed on a scale of either 1 to 100uV or 3 to 300uV (within the graticule area). A1 is printed on the trace to indicate that the amplitude distribution from channel A is on the 1-100uV scale. B3 indicates that the distribution on channel B is on the 3 to 300uV scale.
The amplitude and frequency plots cut-out to below their base lines when the input channel overloads, and also for 12 seconds when the input channel is automatically changed, as at B3.
Rewritten and reproduced with permission from "The cerebral function analysing monitor: initial clinical experience, application and further development", D E Maynard and J L Jenkinson, Anaesthesia, 1984, Volume 39, pages 678-690.Published by Blackwell Science. http://www.blackwell-science.com/ana
