Optimizing hyperbaric oxygen initiation time in carbon monoxide poisoning: a 3-hour window enhances neurological recovery via lactate clearance.

Objectives: To explore the optimal initiation time of hyperbaric oxygen therapy (HBOT) for moderate-to-severe acute carbon monoxide poisoning (ACOP) and to assess the prognostic value of lactate clearance and early MRI findings. Methods: This single-center retrospective study included 12 ACOP patients (2020-2023) treated with HBOT within 6 h after admission. Patients were categorized by HBOT initiation time: early (≤3 h, n=8) and delayed (>3 h, n=4). Clinical, biochemical, and imaging data were analyzed. Primary outcomes were time to regain consciousness and Barthel Index at 6 months. Results: Median HBOT initiation was 112 min. Early treatment was associated with faster organ function recovery (greater SOFA score reduction, p<0.05). Lactate normalized within a median of 17.5 h, and clearance >50 % in 24 h correlated with better neurological outcomes (p=0.002). MRI detected early globus pallidus injury more sensitively than CT. At 6 months, 83.3 % recovered functionally; one developed delayed encephalopathy. Conclusions: Early HBOT initiation (≤3 h) may facilitate metabolic and neurological recovery in ACOP. Early lactate clearance and MRI findings may serve as prognostic markers. Given the small sample size and absence of a non-HBOT control group, these results are exploratory and require confirmation in larger studies.