Background and Rationale:

Cerebrovascular disease is always ranked at the top causes of death and most of hospitalized
acute stroke patients have ischemic stroke [1].

Although the mortality rate of acute ischemic stroke is less than that of hemorrhagic stroke
[1], it still results in patient disabilities and complications that often lead to
significant costs to individuals, families, and society.

Traditional treatment for acute ischemic stroke includes thrombolytic therapy by injecting
tissue plasminogen activator (t-PA) within three hours after onset of symptoms [2],
antiplatelets and/or anticoagulant agents administered within the first 48 hours. Clinically,
the narrow time window of thrombolytic therapy and coexisting contraindications limit the use
of t-PA [2]. Thus, searching for an effective supplemental treatment for acute ischemic
stroke is imperative.

Hyperbaric oxygen therapy (HBOT) is valuable in treating acute carbon monoxide poisoning
[3,4], air or gas embolism [5], facilitating wound healing [6] and has been used as an
adjuvant treatment for many neurological disorders that need further study as concussion [7]
, stroke [8,9], cerebral palsy [ 10],traumatic brain injury [ 11], cerebral air embolism
[12], Autism [13] and multiple sclerosis [14].

Indications of hyperbaric oxygen therapy recommended by undersea and hyperbaric medical
society (UHMS) [15] are 1.air or gas embolism [5], 2.carbon monoxide poisoning [3,4],
3.clostridial myositis and myonecrosis [16], 4.crush injury, compartment syndrome and other
acute traumatic ischemias [17], 5.decompression sickness [18], 6.arterial insufficiencies
[19], 7.severe anemia [20], 8.intracranial abscess [21], 9.necrotizing soft tissue infections
[22],10. refractory osteomyelitis [23], 11.delayed radiation injury [24], 12.compromised
grafts and flaps [25], 13.acute thermal burn injury [26] and 14.idiopathic sudden
sensorineural hearing loss [27].

Known mechanisms of HBOT-induced neuroprotection include enhancing neuronal viability via
increased tissue oxygen delivery to the area of diminished blood flow, reducing brain edema,
and improving metabolism after ischemia [28,29]. Furthermore, a recent study performed on a
rat suggested that upregulation of the expression of glial derived neurotrophic factor (GDNF)
and nerve growth factor (NGF) might underlie the effect of HBOT [30].

The effectiveness of use of Hyperbaric oxygen therapy in human ischemic stroke is still
controversial that need further evaluation.