Oxygen therapy in permanent brain ischemia: potential and limitations

Area of Science:

• Neuroscience
• Ischemic Stroke Research
• Oxygen Therapy

Background:

• Normobaric (NBO) and hyperbaric (HBO) oxygen therapy are known neuroprotective agents in transient cerebral ischemia.
• Their efficacy in permanent ischemia models, which are more representative of clinical strokes, remains unclear or controversial.
• This study aimed to compare NBO and HBO in permanent ischemia models, exploring time windows and combination therapies.

Purpose of the Study:

• To compare the neuroprotective effects of NBO and HBO in two distinct models of permanent middle cerebral artery occlusion (MCAO).
• To investigate the impact of treatment timing on the efficacy of oxygen therapies.
• To evaluate the potential benefits of combining NBO and HBO treatments.

Main Methods:

• Permanent MCAO was induced using coagulation or filament methods in mice.
• Animals were treated with air, NBO, or hyperbaric oxygen (HBO) at 3 atmospheres absolute (ata).
• Infarct volumes were quantified at 7 days (coagulation model) and 24 hours (filament model).

Main Results:

• Following MCA coagulation, both NBO and HBO significantly reduced infarct size when initiated 45 or 120 minutes post-MCAO, with HBO being more potent.
• Repeated HBO treatments did not offer additional benefits.
• Combination therapy (NBO + HBO) resulted in smaller cortical infarcts than NBO alone.
• In contrast, no significant differences in infarct volume were observed in the filament-induced permanent MCAO model among air, NBO, and HBO groups.
• HBO demonstrated significant infarct reduction in filament-induced transient MCAO.

Conclusions:

• Both NBO and HBO exhibit neuroprotective effects against permanent cortical ischemia.
• Hyperbaric oxygen therapy is more effective than normobaric oxygen therapy in this context.
• The effectiveness of oxygen therapy in extensive focal ischemia is contingent upon early recanalization.