Scientists have countered findings of previous clinical trials by showing that giving supplemental oxygen to animals during a stroke can reduce damage to brain tissue surrounding the clot. The timing of the delivery of 100% oxygen – either by mask or in a hyperbaric chamber – is critical to achieving the benefit, however.
"The use of supplemental oxygen after blood flow is restored in the brain appears to actually cause harm by unleashing free radicals," said Savita Khanna, assistant professor of surgery at Ohio State University and principal investigator of the research. "The resulting tissue damage was worse than stroke-affected tissue that received no treatment at all."
Previous clinical trials in humans have suggested that administering oxygen under pressure could harm stroke patients. But the studies did not take into account the status of blood flow in the brain at the time the oxygen was delivered, Savita Khanna noted. The types of stroke under study are ischaemic, meaning a clot is blocking blood flow in the brain, rather than hemorrhagic – strokes that occur when blood vessels rupture in the brain.
However, technology doesn't yet allow for quick and continuous real-time measurement of blood flow in the brain in a hospital. This means clinicians treating stroke patients cannot risk administering hyperbaric oxygen that could do more harm than good if it is not timed properly.
"Hyperbaric oxygen during stroke shows the promise of being an effective tool, but there are things that need to occur before this can be applied in a clinical setting," said Cameron Rink, assistant professor of surgery at Ohio State and a co-investigator on the research. "We need to find better ways to monitor blood flow in humans in real time."
Rink presented the research during a poster session at the Society for Neuroscience annual meeting in Chicago.
