Restrictive Oxygen Targets Linked to Higher Death Risk in Ventilated Stroke Patients

One of the most routine decisions in an intensive care unit—where to set the oxygen saturation target on a ventilator—may carry life-and-death consequences for stroke patients, according to a large new analysis drawing on the health records of more than 17,000 mechanically ventilated adults. The study, published in Frontiers in Neurology, found that patients kept at conservative oxygen saturation levels during the first 48 hours of mechanical ventilation had a significantly higher risk of dying within one and three months than patients maintained at higher saturation levels. The signal was strongest in acute ischemic stroke, the most common form of stroke, and appeared to be absent in intracerebral hemorrhage, a finding that suggests oxygen therapy in the brain-injured may need to be tailored to the specific type of injury rather than borrowed wholesale from general critical care practice.

The research team, led by investigators affiliated with Southern Illinois University School of Medicine, Wayne State University School of Medicine, and collaborating institutions, mined the TriNetX database, a federated network of de-identified electronic health records spanning the years 2006 to 2026. They identified adults with a stroke diagnosis who required invasive mechanical ventilation within 48 hours of stroke onset and who had documented pulse oximetry readings in that same early window. Patients were classified as receiving a restrictive oxygenation strategy if every recorded peripheral oxygen saturation, or SpO₂, value fell between 92 and 96 percent, and as receiving a liberal strategy if all values were at or above 97 percent. Anyone whose readings straddled both ranges or dipped below 92 percent was excluded, a deliberately strict rule designed to create two cleanly separated, non-overlapping exposure groups.

Of the 17,207 patients who met the inclusion criteria, 2,366 had restrictive oxygenation profiles and 14,841 had liberal profiles before any statistical adjustment. Because patients who end up on conservative oxygen protocols often differ systematically from those kept at higher saturations—older, sicker, with more cardiopulmonary disease—the researchers used propensity score matching, a statistical technique that pairs patients with similar baseline characteristics. The model accounted for age, sex, race and ethnicity, body mass index, a Glasgow Coma Scale score of nine or below, and a long list of comorbidities including hypertension, ischemic heart disease, heart failure, atrial fibrillation, chronic obstructive pulmonary disease, pneumonia, and shock. After matching, 2,350 patients remained in each group, and all measured covariates were well balanced, with standardized mean differences below 0.1.

The results were striking. In the matched cohort, restrictive oxygenation during the first 48 hours of ventilation was associated with a 13 percent higher hazard of death at one month, with a hazard ratio of 1.13 and a 95 percent confidence interval of 1.03 to 1.23, a statistically significant finding with a p-value of 0.008. The association persisted at three months, with a hazard ratio of 1.11 and a confidence interval of 1.02 to 1.20. Kaplan–Meier survival curves, which track survival over time, visibly separated between the two groups in the combined stroke population, indicating that the mortality gap emerged early and persisted through the follow-up period.

When the investigators split the population by stroke subtype, the picture became more nuanced. In the acute ischemic stroke subgroup, built from 1,214 restrictive and 7,463 liberal patients before matching, restrictive oxygenation was associated with a 26 percent higher hazard of death at one month (hazard ratio 1.26, 95 percent confidence interval 1.11 to 1.43) and a 22 percent higher hazard at three months (hazard ratio 1.22, 95 percent confidence interval 1.08 to 1.37). In the intracerebral hemorrhage subgroup, however, the corresponding hazard ratios—1.09 at one month and 1.11 at three months—had confidence intervals that crossed one, meaning no statistically significant difference could be detected. The authors note that the hemorrhagic subgroup was smaller, with 728 patients per arm after matching, so limited statistical power may have masked a real effect; notably, the point estimates trended in the same direction as those seen in ischemic stroke.

The biology behind these findings is grounded in the peculiar physiology of the acutely injured brain. In the first two days after an ischemic stroke, cerebral autoregulation—the mechanism that normally keeps blood flow constant across swings in blood pressure—is often impaired. Surrounding the core of dead tissue lies the penumbra, a zone of hypoperfused but still viable brain that depends precariously on whatever oxygen the circulation delivers. Even modest reductions in arterial oxygen content could, in theory, tip penumbral tissue into irreversible infarction, extending the damage and worsening outcomes. A restrictive saturation target of 92 to 96 percent, while safe for many critically ill patients, may leave less reserve for this vulnerable tissue than a liberal target of 97 percent or above.

Yet the push toward conservative oxygen in intensive care has its own logic. Excess oxygen generates reactive oxygen species, drives oxidative stress, and can cause cerebral vasoconstriction, and randomized trials in general ICU populations—including ICU-ROX and the Oxygen-ICU trial—have explored whether tighter oxygen control reduces harm. The new study suggests that extrapolating those protocols to stroke patients may be misguided. The authors point to post-hoc analyses of ICU-ROX as a telling parallel: among ventilated patients with acute brain pathologies other than hypoxic-ischemic encephalopathy, 180-day mortality was numerically higher under conservative oxygen (34.5 percent versus 26.9 percent), a heterogeneity considered plausible enough to be formalized as a prespecified hypothesis in the ongoing Mega-ROX Brains trial, which is randomizing brain-injured patients to conservative or liberal oxygenation targets.

Among the secondary outcomes, one result stood out as counterintuitive: patients in the restrictive group were significantly less likely to undergo tracheostomy within 30 days, at 8.5 percent versus 13.1 percent in the liberal group, a risk ratio of 0.653 with a p-value below 0.001. The authors caution that this pattern may reflect survivorship bias—patients who die early cannot receive a tracheostomy—or may be shaped by unmeasured factors such as the reasons for intubation, the trajectory of neurological recovery, and goals-of-care discussions that could not be captured in the database. Ventilator-associated pneumonia, by contrast, showed no significant difference between groups, with event rates of 0.6 percent and 0.89 percent, though the very low number of events limited statistical power.

The study’s observational design imposes important caveats. Because oxygenation was observed rather than allocated, residual confounding by unmeasured variables cannot be excluded, and the association cannot be read as proof of causation. Stroke severity measures such as infarct volume, hematoma size, and detailed neurological examinations were not available in the federated record network and could not be incorporated into the matching model. The exposure was defined by documented pulse oximetry readings rather than continuous arterial oxygen measurements, so the analysis reflects oxygenation strategy rather than precise quantification of hyperoxemia or hypoxemia. The two saturation thresholds are also adjacent, making the contrast between groups relatively narrow, and follow-up was limited to three months.

Even with those limitations, the sheer size of the cohort and the rigor of the matching make this one of the most pointed challenges yet to the assumption that conservative oxygen targets are universally safe. The authors frame their findings as hypothesis-generating rather than practice-changing, but the implication is hard to ignore: the first 48 hours of mechanical ventilation may represent a modifiable window in stroke care, and the optimal saturation target may differ between an ischemic brain starved of blood flow and a hemorrhagic brain compressed by expanding blood. As stroke remains a leading cause of death and disability worldwide, the authors argue that disease-specific randomized trials—rather than broad ICU-wide oxygen protocols—are urgently needed to determine whether liberal oxygenation genuinely protects the penumbra, or whether individualized titration can balance the competing risks of hypoxemia and oxygen toxicity in this uniquely vulnerable population.

Subject of Research: Oxygen saturation targets and short-term mortality in mechanically ventilated stroke patients

Article Title: Association of liberal versus restrictive oxygen saturation targets with mortality in mechanically ventilated stroke patients: a multicenter retrospective propensity-matched analysis

Article References: Ghafarian, A., Saad, J., Wajahath, M., Ghafarian, M., Saasouh, W., Saleh, K., Nasser, M., Badami, A., Shahait, A. D., & Loggini, A. (2026). Association of liberal versus restrictive oxygen saturation targets with mortality in mechanically ventilated stroke patients: a multicenter retrospective propensity-matched analysis. Frontiers in Neurology, 17, 1840183. https://doi.org/10.3389/fneur.2026.1840183

Image Credits: AI Generated

DOI: 10.3389/fneur.2026.1840183

Keywords: stroke, mechanical ventilation, oxygen saturation, acute ischemic stroke, intracerebral hemorrhage, mortality, propensity score matching, critical care, neurocritical care, TriNetX, hyperoxia, ventilator-associated pneumonia