Hyperbaric oxygen therapy in experimental and clinical stroke

Stroke, which is defined as a neurologic deficit caused by sudden impaired blood supply, has been considered as a common cause of death and disability for decades. The World Health Organization has declared that almost every 5 seconds a new stroke occurs, placing immense socioeconomic burdens. However, the effective and available treatment strategies are still limited. Additionally, the most effective therapy, such as thrombolysis and stenting for ischemic stroke, generally requires a narrow therapeutic time window after the event. A large majority of patients cannot be admitted to hospital and receive these effective treatments for reperfusion timely. Hyperbaric oxygen therapy (HBOT) has been frequently applied and investigated in stroke since 1960s. Numerous basic and clinical studies have shown the beneficial efficacy for neurological outcome after stroke, and meanwhile many underlying mechanisms associated with neuroprotection have been illustrated, such as cerebral oxygenation promotion and metabolic improvement, blood-brain barrier protection, anti-inflammation and cerebral edema, intracranial pressure modulation, decreased oxidative-stress and apoptosis, increased vascular and neural regeneration. However, HBOT in human stroke is still not sufficiently evidence-based, due to the insufficient randomized double-blind controlled clinical studies. To date, there are no uniform criteria for the dose and session duration of HBOT in different strokes. Furthermore, the additional effect of HBOT combined with drugs and other treatment strategies are being investigated recently. Therefore, more experimental and clinical research is imperative to identify the mechanisms more clearly and to explore the best protocol of HBOT in stroke treatment.