Improving ECT seizure quality could help clinicians refine treatment, but adjusting ventilation may offer less predictable benefits than expected. A new Scientific Reports study found no significant association between lower carbon dioxide levels before stimulation and better seizure quality scores.
The findings leave an important question open: when hyperventilation changes a seizure, does it improve the features that matter for treatment?
Why Longer Seizures Do Not Tell The Whole Story
Electroconvulsive therapy involves inducing a controlled seizure under anesthesia. Clinicians evaluate seizure characteristics alongside the patient’s clinical response when making treatment decisions.
Duration is an accessible measurement, but additional seconds do not automatically establish better seizure quality or greater symptom improvement. Electrical brain activity, anesthetic effects, stimulation settings, and patient characteristics complicate that relationship.
Hyperventilation is one technique used during preparation. Increasing ventilation lowers carbon dioxide, potentially making seizures easier to induce or sustain. Its influence on broader quality measures remains less certain.
Testing ECT Seizure Quality In Routine Care
Rebecca Paetow and colleagues retrospectively examined treatment records from RWTH University Hospital Aachen in Germany. Their dataset included 732 bilateral ECT sessions involving 68 adults treated during 2023.
The researchers examined carbon dioxide measured at the end of exhalation, known as end-tidal CO₂, alongside anesthetic choice and electrode placement. Treatment protocols targeted values below 30 mmHg.
Their statistical models accounted for repeated sessions within individual patients. This matters because hundreds of treatments from a relatively small patient group cannot be treated as hundreds of independent participants.
Lower end-tidal CO₂ was not significantly associated with improved quality scores. Interactions involving ventilation, anesthesia, and electrode placement also failed to show statistically significant benefits. Older age consistently predicted lower scores.
A Physiological Rationale With An Uncertain Payoff
Hyperventilation reduces circulating carbon dioxide and raises blood pH, producing respiratory alkalosis. These changes can increase neuronal excitability and influence seizure activity.
However, a physiological effect does not guarantee a better therapeutic seizure. Ventilation operates within a treatment environment shaped by anesthesia, electrical stimulation, medications, and individual neurobiology.
The distinction becomes clearer when the new findings are compared with a 2025 systematic review and meta-analysis of randomized trials.
Across seven studies covering 620 ECT sessions, hyperventilation increased motor seizure duration by approximately 2.9 seconds and electroencephalographic seizure duration by approximately 5.4 seconds.
Those findings support an effect on duration. They do not establish that hyperventilation improves depression outcomes, cognition, or broader seizure quality. Most included studies relied on duration, and the review identified substantial concerns about bias.
Different Measurements Can Produce Different Answers
The two publications therefore address overlapping but distinct questions. Randomized evidence suggests hyperventilation can lengthen seizures. The newer observational study asks whether lower carbon dioxide corresponds to better overall quality scores within routine bilateral treatment.
These results can coexist. A seizure may last longer without showing a measurable improvement on another assessment.
Likewise, the absence of a statistically significant association does not prove that ventilation has no effect. Small benefits, differences between patient groups, or measurement variability could remain undetected.
Seizure scores also remain intermediate measures. They should not be interpreted as direct substitutes for recovery, functioning, or treatment tolerability.
From Ventilation Targets To Patient Outcomes
The practical implication is to evaluate hyperventilation within the full ECT procedure rather than assume that lower carbon dioxide will reliably improve treatment.
Future prospective studies should standardize ventilation, document anesthetic timing and concurrent medications, and examine seizure characteristics alongside symptom change and cognitive outcomes.
For patients, the findings do not establish that hyperventilation improves or worsens recovery. For clinicians, they reinforce the need to interpret procedural measurements in context.
Hyperventilation remains a plausible tool for influencing seizure activity. Whether it reliably improves ECT seizure quality, and whether that translates into better clinical outcomes, requires stronger evidence.
Citations
- Paetow R, Frodl T, Hill A, Grözinger M. Seizure quality in bilateral electroconvulsive therapy: the influence of hyperventilation, electrode placement, and anesthesia. Scientific Reports. 2026;16:33395.
- The impact of hyperventilation on seizure duration following electroconvulsive therapy: a systematic review and meta-analysis of randomized trials. BMC Psychiatry. 2025;25:661.
Explore more at Interventional Psychiatry Network.
