THE ESSENTIAL
- American researchers have developed gas microbubbles that deliver precise quantities of oxygen.
- Sensitive to pH, these can be delivered in high doses, without causing obstruction of blood flow, because they dissolve quickly.
- In pigs with profound hypoxemia due to acute and temporary airway obstruction, this administration of oxygen improves survival by preventing catastrophic organ damage.
In the event of acute respiratory or cardiac arrest, hypoxemia, i.e. low blood oxygen saturation, may occur. In this situation, you must react quickly, because this reduction can cause organ damage or lead to death within a few minutes. Problem: Methods to increase low oxygen levels are ineffective.
“When conventional interventions fail, intravenous oxygen administration can save patients from severe hypoxemia, but at the risk of microvascular obstruction and toxicity of the carrier material,” according to cardiologists at Boston Children’s Hospital (USA). But good news was recently announced by these doctors. After 15 years of research, they developed a safe and effective method of delivering oxygen for these emergencies: injectable oxygen carried into the bloodstream by a rapidly dissolving microbubble of gas.
Oxygen: a microbubble that dissolves quickly and can therefore be injected in large quantities
In order to develop this device, they carried out several experiments as part of a study. The team first tested lipid-coated microbubbles, but the bubbles bound together in the bloodstream and would have caused a fatal embolism if they had not been injected at a precise rate. From this failure, scientists realized that they needed to design bubbles in a way that would prevent them from coming together. So, in a second attempt, they focused on hollow-core polymer microparticles, but these failed to deliver a significant amount of gas to the circulation.
Third, the authors combined the best aspects of their previous approaches. They then developed microbubbles with a solid polymer shell, which dissolve, after being triggered by blood pH, into tiny soluble molecules that can then be excreted from the body. This composition keeps the drug stable during storage and allows it to be injected in critical situations, such as cardiac arrest.
In case of hypoxemia, injected oxygen microbubbles improve survival
Then, the researchers wanted to test this device. To do this, they injected these microbubbles which transport high volumes of oxygen (350 to 500 ml of oxygen per liter of foam) into pigs suffering from profound hypoxemia due to acute and temporary (12 minutes) obstruction of the upper airways. In surviving animals, this oxygen administration led to maintenance of critical oxygenation, reduced risk of cardiac arrest, improved survival, and substantial improvement in neurological and renal function.
“Injecting gas into the bloodstream is considered a horrible idea, and people would be afraid of this solution in itself. But as long as this bubble dissolves quickly, a lot of it can be injected. This opens the way to creating potential of a controlled and predictable means of providing necessary oxygen in cases of hypoxemia, cardiac arrest and other states of shock”, declared the authors of the work published in the journal Nature Biomedical Engineering. After the results were published, the team received a competitive grant to begin manufacturing and testing the drug in preparation for a clinical trial.
