Seizure duration in unilateral electroconvulsive therapy. The effect of hypocapnia induced by hyperventilation and the effect of ventilation with oxygen.

Seizure duration in unilateral electroconvulsive therapy (ECT) was recorded by means of EEG in an intraindividual comparison under different alveolar O2- and CO2-concentrations. Hypocapnia induced by hyperventilation to an alveolar CO2-concentration of 2% (2 kPa) resulted in a highly significant increase in seizure duration compared to a normal CO2 of 5%, when the alveolar O2-concentration was constant at 92%. Oxygen ventilation to an alveolar O2-concentration of 92% gave no significant increase in seizure duration compared to 15%, obtained by ventilation with air, when the CO2-concentration was kept constant at 5%. Seizure duration seems to augment progressively with decreasing alveolar CO2-concentration.