It seemed like news worthy only of the prize it was awarded in 2024, the Ig Nobel (an “honour” bestowed each year, during a ceremony at the Massachusetts Institute of Technology Museum, to the most bizarre achievements, which first “make people laugh, and then think,” according to the definition provided by the founder himself, Marc Abrahams). Nonetheless, enteral ventilation, also called intestinal respiration, presented in 2021 by a group of Japanese and American researchers after lengthy tests on various types of mammals, could become something very serious – in other words, one of the options available to doctors and technicians who need to quickly provide additional oxygen to people whose airways are blocked.
A new study published in the scientific journal Med, by the Cell group, in fact shows that this “bizarre” technique (administration of a special hyper-oxygenated liquid into the colon using an enema-like procedure in order to transfer oxygen to the blood through the intestinal wall instead of via the lungs) can be safely trialled in humans as well.
The idea comes from far away, from observations of the behaviour of certain species of fish, such as the loach, that feed near to the water’s sandy or muddy bottom, where their gills are insufficient for extracting oxygen from the water. To deal with this problem, the loach swallows air when it is at the surface, accumulating it in its intestine. When, on the bottom, it is experiencing difficulty, the fish absorbs oxygen through the intestine itself. For human beings, the circumstances are obviously quite different, but perhaps we, too, could get oxygen, in an emergency situation, using this alternative route.
The authors of the study (researchers from four Japanese universities and the University of Cincinnati in the United States) based their work on that of the American Leland Clark, a former researcher at Cincinnati Children's Hospital Medical Center and a pioneer in these techniques, who developed a liquid known as conjugated perfluorocarbon, capable of transporting large amounts of oxygen, a bit like the blood does.
An attempt to use perfluorocarbon as artificial blood failed, but the hyper-oxygenated substance was never entirely set aside, and animal trials (on rodents and pigs) to test its capacity to deliver oxygen to the blood through the colon have continued and been successful.
Now, as mentioned above, researchers have decided to move on to human beings as well, at least to assess the tolerability (and possible toxicity) of the method. The study just published in Med involved 27 healthy young men in Japan, who were asked to hold different amounts of perfluorocarbon (up to one and a half litres) in their colons for 60 minutes. Those administered the higher amounts reported bloating and abdominal pain, but no serious adverse events were relayed. The results appear encouraging, because general clinical parameters, including markers for the kidneys and liver, remained within normal limits, and there was no unexpected or excessive absorption of the perfluorocarbon.
“This is the first data on humans, and the results are limited to proving the procedure’s safety, not its efficacy,” explains Takanori Takebe, coordinator of the study and professor at the University of Osaka and that of Cincinnati. “However, now that we have proven its tolerability, we can move on to assessing the effectiveness of the process in delivering oxygen to the bloodstream.”
If the results of the new trials are also positive, applications for enteral ventilation could include acute cases where the airways are blocked by lesions or inflammation or when lung function is severely reduced by infections or other complications, and mechanical ventilators are insufficient to the task. In such cases, having a second means by which to rapidly deliver oxygen to the body could be of considerable help, while also giving the lungs a chance to rest.