The concept, while sounding like a novelty, builds on decades of animal research and could offer a low-tech, emergency solution for patients whose lungs are no longer functioning. The first clinical test in humans suggests the method—known as enteral ventilation via anus (EVA)—is physically tolerable and has cleared an essential safety hurdle.
Inspired by a natural survival mechanism found in some aquatic species, scientists from Cincinnati Children’s Hospital and the University of Osaka are exploring whether oxygen can be absorbed through the gut. When the COVID-19 pandemic intensified demand for alternative ventilation strategies, this unorthodox method—once ridiculed—re-emerged as a potentially viable option for critical care.
A Method Rooted in Animal Biology
The research is based on an unlikely source: the loach, a bottom-dwelling fish capable of intestinal breathing. When its gills can’t handle the oxygen load, the loach draws air through its digestive tract. Other animals, including sea cucumbers and certain turtles, have shown similar abilities.
According to ZME Science, this phenomenon inspired scientists to ask if a comparable method could help humans during respiratory failure. The idea gained traction in 2021, when mice and pigs were successfully oxygenated using oxygen-rich perfluorocarbon enemas. The animals, despite artificially induced breathing problems, survived without major complications.
The procedure, still in its experimental phase, uses perfluorocarbons—a type of chemical liquid capable of dissolving large volumes of oxygen. These substances are not new. A version called Oxycyte was developed in the 1960s as an artificial blood substitute by Cincinnati researcher Leland Clark and later inspired scenes in James Cameron’s 1989 film The Abyss.
The First Human Trial and Its Results
In 2024, the team led by Takanori Takebe launched the first human study to test whether EVA could be safe for people. Conducted in Japan, the trial involved 27 healthy male volunteers, who received between 25 and 1,500 milliliters of non-oxygenated perfluorocarbon liquid via the rectum.
Participants were asked to retain the liquid for an hour. The aim was not yet to deliver oxygen but to monitor how the human body responded to the process. The trial showed promising tolerance: 20 out of 27 subjects completed the full duration.
Some volunteers who received the highest doses reported temporary bloating and abdominal discomfort, but no serious side effects occurred. Vital signs such as heart rate and blood pressure remained within normal range. “Now that we have established tolerance,” said Takebe, “the next step will be to evaluate how effective the process is for delivering oxygen.”
Towards a New Emergency Care Tool
If future trials prove the method can successfully transfer oxygen into the bloodstream, EVA may offer a non-invasive backup for mechanical ventilation. As ZME Science explains, the technique could reduce the risk of further lung injury by allowing the respiratory system to rest while oxygen is delivered through the colon.
Takebe’s team sees potential beyond adult emergency care. Neonatal intensive care units, for example, may benefit from EVA in supporting premature babies with underdeveloped lungs. To accelerate the process, the researchers have founded a startup, EVA Therapeutics, focused on funding and coordinating new studies.
For now, the idea of humans “breathing through their butts” remains mostly symbolic—but history shows that unusual ideas can evolve into practical medical solutions. What began as a subject of mockery—earning the team an Ig Nobel Prize in 2024—may yet find its place in the future of critical care.