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RESEARCHERS in the US have developed oxygen-filled microparticles which can be injected directly into the bloodstream of a patient to almost instantly oxygenate the blood.

When starved of oxygen for a period of time, for example in acute lung failure or due to blocked airways, patients often suffer a heart attack or damage to organs, including the brain. The particles, which are injected in the form of a foam suspension, can oxygenate the blood within seconds and give paramedics or intensive care staff extra time to stabilise patients and administer life-saving treatments, such as inserting a breathing tube or connecting them to a heart and lung machine.

The multidisciplinary team, led by John Kheir, a cardiologist at Boston Children’s Hospital, included doctors, particle scientists, and chemical engineers. Kheir says that he began investigating the possibility of injectable oxygen after a young girl in his care starved of oxygen due to severe pneumonia died before she could be connected to a heart and lung machine in 2006.

The microparticles measure 2–4 µm in diameter and consist of a layer of single lipids surrounding a small pocket of oxygen. The team used a sonicator to make the particles, in which the oxygen and lipids are mixed together using high-intensity sound waves. The microparticles then self-assemble. Oxygen gas makes up around 70% of the final liquid, three to four times the amount carried by human red blood cells.

In animal tests, the suspension re-oxygenated blood to near-normal levels within seconds, and kept animals whose airways were completely blocked alive for 15 minutes, with much lower levels of heart attack and organ injury than a control group. Kheir said, however, that some of the most “convincing” experiments came from tests on samples of the researchers’ own blood. Blue, deoxygenated blood in a test tube turned bright red as soon as the microparticles were added.

“This is a short-term oxygen substitute — a way to safely inject oxygen gas to support patients during a critical few minutes. Eventually, this could be stored in syringes on every code cart in a hospital, ambulance or transport helicopter to help stabilise patients who are having difficulty breathing,” says Kheir.

Science Translational Medicine DOI: 10.1126/scitranslmed.3003679