How short high-oxygen exposures affect brain blood flow during mechanical ventilation

HYPERMIND - Hyperoxia Effects on Cerebral Hemodynamics

We will test whether brief, controlled increases in ventilator oxygen change brain blood flow in adults who are intubated and on mechanical ventilation in the ICU.

Quick facts

• Phase: NA
• Study type: Interventional
• Enrollment: 80 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: Erasme University Hospital (other)
• Locations: 1 site (Brussels)
• Trial ID: NCT07377162 on ClinicalTrials.gov

What this trial studies

Mechanically ventilated adult ICU patients will undergo stepwise increases in the fraction of inspired oxygen (FiO2) while continuous transcranial Doppler (TCD) monitoring of the middle cerebral artery records cerebral blood flow velocity. Patients with baseline FiO2 < 0.5 will receive two hyperoxic steps (FiO2 0.5 then 1.0) and those with baseline FiO2 ≥ 0.5 will receive a single step (FiO2 1.0), each with a ~5-minute stabilization and a 10-minute recording period. Arterial blood gases will be sampled at baseline, at the end of each hyperoxic step, and after return to baseline, while ventilation, sedation, and vasoactive drug rates are kept constant. The protocol uses non-invasive monitoring and no additional invasive procedures beyond standard ICU care.

Who should consider this trial

Good fit: Adults (≥18) in the ICU who are intubated and on volume-controlled mechanical ventilation for ≤72 hours, have PaCO2 35–45 mmHg, invasive arterial monitoring, and an adequate TCD acoustic window are ideal candidates.

Not a fit: Patients on ECMO or continuous renal replacement therapy, pregnant patients, those without a usable TCD window, or those with severe hemodynamic instability likely will not benefit from this protocol.

Why it matters

Potential benefit: If successful, this could help clinicians set oxygen levels that avoid harmful changes in brain blood flow for ventilated ICU patients.

How similar studies have performed: Prior physiological studies in volunteers and some patient groups have shown that hyperoxia can reduce cerebral blood flow, but continuous TCD data in mechanically ventilated ICU patients are limited.

Eligibility criteria

Inclusion Criteria

* Adult patients aged ≥18 years
* Admitted to the intensive care unit (ICU)
* Intubated and mechanically ventilated for ≤72 hours
* Receiving volume-controlled mechanical ventilation
* Arterial partial pressure of carbon dioxide (PaCO₂) between 35 and 45 mmHg
* Invasive arterial blood pressure monitoring in place
* Adequate transcranial Doppler (TCD) acoustic window
* Clinically judged to be suitable for a brief normobaric hyperoxic stimulus
* Expected to receive one or two hyperoxic steps based on baseline FiO₂ requirements: a) Baseline FiO₂ \< 0.5: two-step hyperoxic stimulus (FiO₂ 0.5 followed by FiO₂ 1.0); b) Baseline FiO₂ ≥ 0.5: one-step hyperoxic stimulus (FiO₂ 1.0)

Exclusion Criteria:

* Age \<18 years
* Pregnancy
* Extracorporeal membrane oxygenation (ECMO)
* Continuous renal replacement therapy (CRRT)
* Contraindications to hyperoxia, as judged by the treating physician
* Severe hemodynamic instability requiring changes in vasopressor dose during the recording period
* Inability to obtain a reliable transcranial Doppler signal through the temporal acoustic windows
* Any clinical condition deemed by the treating physician to pose unacceptable risk during hyperoxic exposure

Where this trial is running

Brussels

• Erasme Hospital - ULB — Brussels, Belgium (RECRUITING)

Study contacts

• Principal investigator: Fabio Silvio Taccone, MD, PhD — Hôpital Erasme - Université Libre de Bruxelles (ULB)
• Study coordinator: Michele Salvagno, MD

Conditions: Hyperoxemia, Cerebrovascular Circulation, Cerebral Autoregulation, Critical Illness, Mechanical Ventilation, hyperoxemia, brain hemodynamics, tcd