Classics in ECT: Bergsholm et al. on Hyperventilation (1984)

"Classics in ECT" brings you this Acta paper from Norwegian investigators:

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

Bergsholm P, Gran L, Bleie H.Acta Psychiatr Scand. 1984 Feb;69(2):121-8. doi: 10.1111/j.1600-0447.1984.tb02475.x.PMID: 6422704

The abstract is copied below:

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.

The pdf is here.

This carefully designed study looked at whether it is oxygen or low CO2 that contributes to seizure prolongation. The short answer is "low CO2," but the reality is a bit more complicated. Further studies in the intervening years have explored various aspects of the pulmonary and cerebral physiology of ECT.

In general, for ECT, "the green gas is good," hyperventilation with 100% oxygen is beneficial in most cases and should be routine, unless there is a reason to avoid it (e.g. first treatment in a young patient).

This paper, presented in the commendably terse and academic Scandinavian style, is worth reading in full (~10 minutes).