The standardization of hyperventilation on EEG recording in childhood. II. The quantitative analysis of build-up.

In thirty-seven children free of neurological symptoms, we attempted the quantitative analysis of EEG slowing during standarized hyperventilation activation, respiration rate of 30/min, a three-fold elevation of VE and duration of 4 minutes. The degree of build-up gradually became mild with increasing age and no build-up was observed in the subjects older than 14 years old. Fast Fourier Transform analysis of the build-up showed that a big build-up was due to both increasing delta and theta power, and markedly decreasing alpha power with markedly increasing total power, and the mild build-up was due predominantly to increasing theta power. These changes disappeared, the levels before the activation being attained again, within one minute after the hyperventilation in almost all subjects. As to age differences in EEG slowing during hyperventilation, an increase in both delta and theta activity was observed in the younger subjects (6-9 years old), and a mild increase in theta activity was predominantly observed in adolescents. On topographic analysis of EEG slowing, the delta power was found to have expanded to the posterior area and the theta power to have expanded to become diffuse. The standardization of hyperventilation in childhood is important for judgement of the build up because of these age differences, and also may be useful for understanding the development of the central nervous system.