Normal slowing during hyperventilation

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During hyperventilation:

  • Bilateral synchronic delta activity
  • Most prominent in the frontal area
  • Generally in persons up to 30 years old
  • Disappears after around 30 seconds after hyperventilation was stopped
  • Prolonged slowing during hyperventilation has no pathologic meaning (sometimes is hypoglycemia the cause)
  • The lack of this response has no pathologic meaning
  • OIRDA (occipital intermittent rhythmic delta activity) during hyperventilation is normal in children, however not in adults
  • Sometimes the alpha rhythm becomes more prominent during hyperventilation, probably due to a relaxing effect of hyperventilation
  • Sometimes the responsiveness decreases during hyperventilation, this altered responsiveness during hyperventilation-induced EEG slowing is a non-epileptic phenomenon in healthy children. [1]

Bilateral synchronic delta activity in the frontal area during hyperventilation (source) Hyperventilation slowing e.png


  1. Epstein et al, Altered responsiveness during hyperventilation-induced EEG slowing: a non-epileptic phenomenon in normal children, epilepsia, 1994 Nov-Dec;35(6):1204-7.