Abstract Patients with acute focal ischemic stroke (AIS) often require intensive care management, including mechanical ventilation and supplemental oxygen. Observational studies suggest a "U"-shaped relationship between PaO2 levels and mortality in AIS, yet the mechanisms driving cerebral and pulmonary damage across different oxygen levels are not well understood. This study aimed to evaluate the extent of brain and lung injury following exposure to varying PaO2 levels in an experimental model of focal AIS. Thirty-two male Wistar rats (CEUA 131/23) underwent focal AIS induced by thermocoagulation of pial blood vessels. After 24 hours, rats were randomly assigned to one of four groups (n = 8 per group): normoxia (NORMO: PaO2 = 80-120 mmHg), hypoxia (HYPO: PaO2 80 mmHg), moderate hyperoxia (MOD: PaO2 = 121-299 mmHg), or severe hyperoxia (SEV: PaO2 ≥ 300 mmHg). Rats were ventilated for two hours with a positive end-expiratory pressure (PEEP) of 1 cmH2O and tidal volume (VT) of 6 ml/kg. Lung function was assessed at the start (INITIAL) and end (FINAL) of the experiment, after which lungs and brains were collected for histological analysis. Results PaO2 levels at FINAL were 95±15 mmHg in the NORMO group, 51±6 mmHg in the HYPO group, 184±52 mmHg in the MOD group, and 350±47 mmHg in the SEV group (p 0.001). Peak and plateau airway pressures increased over time across all groups (p 0.001), with no significant differences among groups at FINAL. Mean arterial pressure remained stable, and hematocrit levels declined in all groups (p 0.006). In the brain, neutrophil infiltration in the ischemic penumbra indicated blood-brain barrier dysfunction. This study demonstrates that targeted oxygenation was successfully achieved across groups without significant differences in respiratory mechanics or hemodynamics. While histological differences in the Diffuse Alveolar Damage Score were observed among the groups NORMO and MOD (13.08 ± 4.04 vs 21.69± 7.46 p = 0.0443). This abstract is funded by: National Council for Scientific and Technological Development (CNPq), Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (FAPERJ), Coordination for the Improvement of Higher Education Personnel (CAPES)
Magalhães et al. (Fri,) studied this question.