Breathing through the rectum? It may be possible - Japanese scientists tested it… and the results are surprising

It seems unlikely, even baffling, but science often advances along unusual paths. According to Euronews, Japanese researchers led by Takanori Takebe have successfully tested a “rectal breathing” technique in animals — and have now taken the first steps in humans.

Takebe, a physician and stem cell biologist, is a recognised figure in academia. He holds the Chair of Organoid Medicine and is director of Commercial Innovation at the CuSTOM Research Centre at Cincinnati Children's Hospital. He has devoted himself to developing laboratory-grown livers to treat liver failure, but it was a fish that occasionally breathes through its intestine that inspired this radical project.

This freshwater fish, when placed in low-oxygen environments, gulps air from the surface and absorbs it through its intestine. A process that, though peculiar, served as the basis for pioneering research.

An alternative route for oxygenation

“There are countless diseases that compromise lung function, such as airway injuries or severe pneumonia”, explains Takebe, quoted by Cincinnati Children's Hospital. “During the COVID-19 pandemic, many patients died because of a shortage of ventilators. We urgently need alternative routes of oxygenation.”

It was in this context that the concept of enteral breathing was born — that is, the delivery of oxygen through the intestine, using a fluid called perfluorodecalin, capable of carrying large quantities of oxygen. When administered rectally, this fluid can be absorbed by the intestinal wall and transferred to the bloodstream.

In tests on rats and pigs, the method proved effective. An enema with 400 millilitres of oxygenated fluid made it possible to maintain blood oxygen levels for about 19 minutes. In more advanced trials, the pigs maintained stable saturation levels for half an hour, Euronews reports.

Initial tests in humans

Next, the scientists moved on to tests in healthy humans, carried out in Japan. 27 male volunteers received non-oxygenated doses of perfluorodecalin, administered rectally, with the aim of assessing the human intestine's tolerance of the fluid.

The doses ranged from 25 millilitres to 1.5 litres — the latter amount corresponds to the maximum limit allowed in radiological examinations with contrast agents. Four of the six volunteers in the group that received 1.5 litres experienced abdominal pain and did not complete the procedure. However, most of those who received up to 1 litre tolerated it well, with only bloating and mild discomfort.

Takebe and his team say that further studies are still needed, above all to improve the delivery system, accurately measure the actual absorption of oxygen, and ensure there are no side-effects.

Unexpected recognition

In 2024, the research earned Takebe an Ig Nobel Prize, a parody of the Nobel prizes awarded to unusual but scientifically valid studies. Organised by the magazine Annals of Improbable Research, the prize recognises discoveries that “first make you laugh, then make you think”.

What seems absurd today may, in the future, save lives — especially in cases of respiratory failure where traditional ventilation is not available. Whether the intestine can really breathe, science is getting ever closer to confirming.