Abstract: Objective Analyze the correlation between the duration of hyperbaric oxygen (HBO) treatment and the reduction of oral medication clonazepam in patients with paroxysmal sympathetic hyperactivity (PSH) after severe brain injury. Method Retrospective inclusion of PSH patients with severe brain injury admitted to the Rehabilitation Center of Fuxing Hospital Affiliated to Capital Medical University from September 2017 to July 2023. Collect general demographic and sociological data, etiology, lesion site, comorbidities, physical examination upon admission (vital signs, muscle tone, joint range of motion), PSH attack characteristics, HBO treatment frequency, PSH treatment drugs and dosage, and other medical records of patients. Multiple logistic regression and rank correlation analysis were used to investigate the correlation between the reduction of clonazepam and the number of HBO treatments. Result A total of 75 PSH patients who met the inclusion and exclusion criteria were selected, including 32 cases (42.7%) of HBO short course (10 treatments) and 38 cases (50.7%) of clonazepam reduction. The reduction rate of clonazepam in patients with long-term HBO treatment (>10 treatments) was higher than that in patients with shortterm HBO treatment (65.1% (28/43) compared to 31.3% (10/32), P<0.05). After adjusting for confounding factors such as tracheostomy, heart rate, joint range of motion, sweating during attacks, and increased muscle tension during attacks, multivariate logistic regression analysis showed a significant correlation (OR=0.27, 95% CI: 0.09-0.82, P<0.05) between long-term HBO treatment and reduction of clonazepam. 75 PSH patients were divided into three groups according to the HBO treatment course, including 32 cases (42.7%) in the HBO 10 dose group, 15 cases (20.0%) in the HBO 20 dose group, and 28 cases (37.3%) in the HBO 30 dose group. The rank correlation analysis between the reduction of chloramphenicol and the number of HBO treatments showed a positive correlation with a correlation coefficient of 0.331 and P=0.004. Conclusion HBO treatment can reduce the dosage of the oral drug clonazepam for PSH, thereby reducing drug-induced side effects and becoming a non pharmacological treatment option for PSH.