Injectable microbubbles help you breathe, keep you alive

These oxygen-filled microparticles deliver 15 minutes worth of oxygen with a single intravenous injection. For patients who aren't breathing, this could prevent heart attacks and brain damage.

For patients with injured lungs, injecting tiny oxygen-filled particles could save lives in emergency rooms and intensive care units.

If you’re in a critical condition and you stop being able to breathe on your own, a doctor will typically use a breathing mask or a tube to deliver oxygen to your lungs. But these procedures aren’t effective if the oxygen deprivation is due to injured lungs.

So, to bypass the lungs, a team led by John Kheir at the Children’s Hospital Boston looked for a way to inject the life-saving oxygen directly into the bloodstream.

They engineered oxygen-containing microparticles capable of delivering 15 minutes worth of oxygen with a single intravenous injection.

  • The microparticles, about 2 to 4 micrometers, are made of phospholipids, or fatty molecules, that hold trapped oxygen. (High-intensity sound waves were used to mix the oxygen and fats together.)
  • The microparticles are suspended in a mixture that looks like shaving cream but floors like water. It carries up to 4 times the oxygen content of our own red blood cells.
  • As soon as the microparticles are in the bloodstream (pictured), the released oxygen gas binds to hemoglobin, the molecule that carries oxygen through the body.
  • As oxygen gas leaves the microparticles, the lipid shell folds and disintegrates.

They injected the foamy mix into rabbits with severe oxygen deprivation from block windpipes. The microparticles reversed the low oxygen levels within seconds.

The current maximum is around 15 to 30 minutes.

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

Doing so decreases the likelihood of potentially fatal complications of oxygen deprivation, such as cardiac arrest or brain injury. And it avoids cerebral palsy resulting from a compromised fetal blood supply.

In the early 1900s, intravenous administration of oxygen often caused dangerous gas embolisms. Here, the gas is packaged into small, deformable particles that can squeeze through capillaries where free gas would get stuck.

Because humans are much larger than rabbits, keeping a person’s blood oxygen levels up during an emergency requires injecting larger volumes continuously: that’s 2 liters of microparticles to keep an adult alive for 10 minutes. Fortunately, hemoglobin picks up oxygen quickly and the empty shell collapses, so the actual volume added to the bloodstream is closer to 600 or 700 milliliters. They’d like to decrease that even more.

If it works in large animal trials currently underway and moves to human clinical trials, the technology – which they’re patenting – could be used on anyone with a lung infection, asthma attack, or blocked airway.

The work was published in Science Translational Medicine yesterday.

Image: D. Kunkel/Dennis Kunkel Microscopy, Inc.; D. Bell/Harvard University; J. Kheir/Children’s Hospital Boston; C. Porter/Chris Porter Illustration

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