Gas-filled microparticles can quickly oxygenate blood

A team led by researchers at Boston Children’s Hospital has designed gas-filled microparticles that can be injected directly into the blood stream to quickly oxygenate the blood.

The microparticles consist of a single layer of lipids (fatty molecules) that surround a tiny pocket of oxygen gas and are delivered in a liquid solution. In an article in the 27 June issue of Science Translational Medicine, John Kheir, managing director of the Department of Cardiology at Boston Children’s Hospital, and colleagues reported that an infusion of these microparticles into animals with low blood oxygen levels restored blood oxygen saturation to near-normal levels within seconds. 

When the trachea was completely blocked, the infusion kept the animals alive for 15 minutes without a single breath and reduced the incidence of cardiac arrest and organ injury.

The microparticle solutions are portable and could stabilise patients in emergency situations, buying time for paramedics, emergency clinicians or intensive care clinicians to more safely place a breathing tube or perform other life-saving therapies, said Kheir in a statement.

‘This is a short-term oxygen substitute — a way to safely inject oxygen gas to support patients during a critical few minutes,’ he said. ‘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.’

The microparticles would likely only be administered for a short time, between 15 and 30 minutes, because they are carried in fluid that would overload the blood if used for longer periods, Kheir said.

He also noted that the particles are different from blood substitutes, which carry oxygen but are not useful when the lungs are unable to oxygenate them. Instead, the microparticles are designed for situations in which the lungs are completely incapacitated. 

In the studies reported in the paper, the team used a sonicator, which uses high-intensity sound waves, to mix the oxygen and lipids together.

The process traps oxygen gas inside particles averaging two to four micrometers in size (not visible without a microscope). The resulting solution, with oxygen gas making up 70 per cent of the volume, mixed efficiently with human blood.

‘One of the keys to the success of the project was the ability to administer a concentrated amount of oxygen gas in a small amount of liquid,’ Kheir said. ‘The suspension carries three to four times the oxygen content of our own red blood cells.’

Intravenous administration of oxygen gas was tried in the early 1900s, but these attempts failed to oxygenate the blood and often caused dangerous gas embolisms. 

‘We have engineered around this problem by packaging the gas into small, deformable particles,’ Kheir said. ‘They dramatically increase the surface area for gas exchange and are able to squeeze through capillaries where free gas would get stuck.’