‘Butt breathing’ could help people who can’t get oxygen the regular way

Takanori Takebe is on a mission to find out if people can breathe through their butts.

As a medical doctor and stem cell biologist, Takebe spends most of his time trying to develop lab-made livers to treat organ failure. His side quest to explore backside breathing began several years ago, when his father caught pneumonia and had to be put on a ventilator.

“I was really shocked by how invasive it is,” says Takebe, of Cincinnati Children’s Hospital Medical Center in Ohio and the University of Osaka in Japan. Takebe worried about how the procedure might affect his dad — who’d already had part of one lung removed due to a past infection — and his father’s lack of other options if the ventilator wasn’t enough. That got Takebe curious whether there was any way to help patients get oxygen into the body without involving the lungs.

Inspiration struck when a graduate student brought a book into Takebe’s lab that described how various animals get oxygen through their skin, genitals or guts. Freshwater fish called loaches, for instance, can swallow air to supplement their gill breathing in low-oxygen water.

With his background in gastroenterology, Takebe knew that the human intestinal tract is rich in blood vessels. That’s why enemas can deliver medicine to the bloodstream. Takebe suspected that perhaps oxygen could pass from the intestines into the bloodstream, too.

Takebe and his colleagues developed an enemalike treatment that sends a liquid called perfluorodecalin up the rectum. This liquid, which is already used in some medical procedures, can be loaded up with oxygen. As it releases that oxygen into the body, space in the liquid’s chemical structure opens to absorb “exhaled” carbon dioxide.

In experiments with mice and pigs, enemas of this super oxygen-rich liquid helped the animals survive low-oxygen conditions. Each 400-milliliter dose boosted pigs’ blood oxygen levels for about 19 minutes at a time. Takebe’s team shared those findings in Med in 2021. Further pig tests reported in 2023 showed the technique could improve animals’ oxygen levels for up to half an hour.

During these experiments, Takebe vividly remembers seeing samples of the pigs’ blood change from a muddy, low-oxygen hue to a brighter, oxygen-rich red. “That was my aha moment,” he says — an indication that this wild idea might actually work.

In 2024, the work won an Ig Nobel Prize — a cheeky award for science that makes people laugh, then think. “Thank you so much for believing in the potential of [the] anus,” Takebe said at the awards ceremony while wearing a loach-shaped hat.

Now, the researchers have tested the safety of butt breathing in people. Twenty-seven healthy male volunteers in Japan each took a dose of non-oxygenated perfluorodecalin up the anus and were asked to hold it for an hour. Those smallest dose group got a squirt of 25 milliliters. The biggest dose was a whopping 1.5 liters — the maximum approved for “contrast agent” liquids used in X-ray scans of the GI tract.

Four of the six men in the planned 1.5-liter group had to stop receiving liquid early due to stomach pain. But most of those who got up to 1 liter fared pretty well, bloating and mild tummy discomfort aside, Takebe’s team reports in the Dec. 12 Med. The research was funded by EVA Therapeutics, a start-up that Takebe cofounded to pursue the project. 

Future clinical trials will show whether an oxygen-loaded version of the liquid actually delivers oxygen to people’s bloodstreams. Excited as Takebe is about this work, he admits that it gets mixed reactions from other doctors and scientists.

One serious skeptic is John Laffey, a clinician and researcher who specializes in acute respiratory distress syndrome at the University of Galway in Ireland. Researchers should focus on improving treatments that support the lungs rather than enlisting other body parts to do lungs’ job, Laffey says. “The lung, even an injured lung, will always exchange gas way better than any other organ, because that’s what it’s designed for.”

Even if people technically can get oxygen through the intestines, sustained oxygen support would require a lot of enemas, over and over. “A liter of perfluorodecalin carries 500 milliliters of oxygen,” Laffey says. “We use 250 milliliters per minute …. A back-of-the-envelope calculation here would tell you it’s just very hard to see how this would work.”

Kevin Gibbs, a pulmonary critical care physician at Wake Forest University School of Medicine in Winston-Salem, N.C., is more intrigued by the proposal. “It definitely raised my eyebrows,” Gibbs says. “As someone who treats a lot of people who have low oxygen levels, I tend to think of myself as an above-the-waist doctor.” But sending oxygen in the back entrance — if it’s shown to work — could be useful in a few cases, he says.

When doctors need to put a tube down someone’s throat to hook them up to a ventilator, for instance, that minutes-long procedure can expose patients to dangerously low oxygen levels, Gibbs says. “What I find exciting is if this drug works … maybe you can administer this, and then all of the sudden they have this real boost in oxygen for the time it takes you to safely put someone on life support — and that would be huge.”

Takebe also envisions intestinal oxygen as a supplement to other types of breathing support or a short-term stopgap when other treatments aren’t available. “Maybe we can apply this in emergency situations, like hospital-to-hospital [transfers] or ambulance procedures,” he says. But that future would still be many years and clinical trials away.

How does Takebe’s father feel about butt breathing as a potential way to help patients like him? “Dad is pleased,” Takebe says. “He’s always offering to be our experimental subject.” That would of course be a huge conflict of interest, Takebe adds. But he appreciates the support.