Abstracts

Hyperventilation (HV) is an important activation procedure during routine pediatric electroencephalograph (EEG) recording. Nevertheless, there is little scientific evidence to allow standardization of the HV procedure, in particular the duration of HV required, to be deemed adequate. We attempt to determine the adequacy of HV in pediatric subjects during EEG recording, by assessing the degree of EEG build-up of slow activity and the corresponding non-invasive end-tidal carbon dioxide (EtCO2) measurement. Following informed consent by the parents or adult caregivers, we assessed a total of 117 pediatric subjects aged 5 to 16 years who were scheduled for routine EEG studies during a 3-year period from April 2002 to March 2005. The inclusion criteria were the subject[apos]s ability to perform adequate HV and a normal waking EEG background. All subjects performed HV for 4 minutes. An electronic metronome was used to synchronize the over-breathing for all subjects in order to achieve an optimal respiratory rate of 30 per minute. A nasal cannula was attached to the subject and the EtCO2 values were recorded using a Nellcor NPB-75 capnometer. The EEG build-up of slow activity was categorized according to the severity of slowing within a 10-second epoch of the EEG recording, as previously reported by Yamatani et al. The four categories consisted of: an increase in amplitude but no intermixed slow waves (+), mild or partial transient slowing (++), moderate slowing (+++), and marked slowing with disappearance of background activity (++++). The mean EtCO2 values and their standard deviations after starting HV were (30.7[plusmn]5.0) mm Hg at 1 minute, (27.7[plusmn]5.0) mm Hg at 2 minutes, (26.2[plusmn]4.8) mm Hg at 3 minutes, and (26.1[plusmn]4.9) mm Hg at 4 minutes. The number of subjects showing the 4 different degrees of EEG slowing at various time periods after commencing HV is shown in the table. Our study showed that when performing hyperventilation, there was a correlation between the EtCO2 values achieved and the degree of EEG slowing present, for the duration of HV till 3 minutes. However, the EtCO2 values and the degree EEG slowing did not show a significant difference between HV for 3 minutes versus HV for 4 minutes. Thus, the results of our study suggest that good hyperventilation effort for 3 minutes is sufficient and this could be used for standardization of the duration of HV required in routine pediatric EEG recording.[table1] (Supported by National Healthcare Group (Singapore) cluster research fund: Grant Number NHG-PRP-01139.)