Diagnostic yield of five minutes compared to three minutes hyperventilation during electroencephalography

Purpose: To investigate whether hyperventilation (HV) for 5 min increases the diagnostic yield of electroencephalography (EEG) compared to 3 min HV. Methods: data were evaluated from 1084 consecutive patients, from three European centres, referred to EEG on suspicion of epilepsy. Seizures and interictal EEG abnormalities precipitated during the first 3 min and during the last 2 min of the HV period (totally 5 min) were determined. Results: Eight hundred seventy-seven patients (81%) completed 5 min HV. Seizures were precipitated during the first 3 min of HV in 21 patients, and during the last 2 min in four more patients. Interictal EEG abnormalities were precipitated in the first 3 min of HV in 16 patients, and during the last 2 min in 7 more patients. Psychogenic nonepileptic seizures occurred in eight patients during the first 3 min of HV and in two more patients during the last 2 min. No adverse events occurred during the last 2 min of HV, but eight patients (1%) stopped HV during the last 2 min because they were not able to hyperventilate further. Conclusion: 16% of seizures and 30% of interictal EEG abnormalities triggered by HV occurred during the last 2 min of HV, suggesting the clinical usefulness of prolonged hyperventilation for 5 min. The vast majority of patients (99%) who are able to hyperventilate for 3 min can complete 5 min HV, without additional adverse events. (C) 2015 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.