Intestinal breathing success during hypoxia

One of the many lessons we learned from the COVID 19 pandemic is the importance of having sufficient ventilators and other breathing aids to save the lives of people in hypoxic respiratory failure - where they are not getting enough oxygen into their blood to survive. Now, a group of scientists have taken inspiration from the aquatic world of sea cucumbers, freshwater fish called loaches, and the so called bum-breathing turtles, to develop a new approach. Termed ‘Enteral ventilation via anus’, the technique uses either a steady oxygen flow or the injection of a highly-oxygenated liquid into the anus, with remarkable, life-saving results in mice, rats, and even pigs. Takanori Takebe of Tokyo Medical and Dental University and Cincinnati Children’s Hospital, and lead author on the study, spoke to Eva Higginbotham…

Eva - Although it might seem strange to us, breathing through your backside has some advantages for the animals that do it. For example, the Fitzroy River turtle in Australia, sometimes affectionately called the bum breathing turtle, can stay underwater for up to three weeks at a time, thanks to this ability. And thanks to new research out of Tokyo's Medical and Dental University and Cincinnati's Children's Hospital, intestinal breathing might soon be something we humans are getting comfortable with.

Takanori - We started looking more carefully about the interanus application of oxygen, which turned out to be very effective.

Eva - That's Takanori Takebe. He and his team have devised two new approaches for getting oxygen into the blood of mice, rats, and pigs, and both take advantage of the fact that the mammalian rectum, that's the last bit of the large intestine before the anus, is both supplied with loads of blood vessels and has a fairly permeable membrane for gases to cross over, making it an excellent part of the body to adapt as another site to breathe from.

Takanori - One is a very intuitive approach we just intubated, from the anus, just to provide oxygen gas continuously. This oxygen delivery is really able to persist survival in lethal conditions. Even up to 60 minutes or even longer.

Eva - 60 minutes of breathing through the rectum just by pumping in oxygen. Sounds amazing, but also like you could get a bit uncomfortable. The more clinically relevant approach uses a liquid that's very good at dissolving oxygen, perfluorocarbon or PFC. This liquid is already used by doctors during some ice surgeries and sometimes as a type of synthetic blood for transfusions. So we already know that it's safe for humans.

Takanori - So that liquid ventilation approach is also having greater impacts on oxygenation. So as to really rescue those fatal hypoxic conditions in the mouse, rats, and pig model system.

Eva - Incredibly, Takanori showed that when just less than a pint of this PFC was injected into the anus of pigs, they would stay happily oxygenated for up to 20 minutes when in respiratory failure. And they didn't stop there, by re-injecting every 20 minutes or so they could keep the pigs going for hours, or even more. Importantly though, when we breathe in and out using our lungs, we aren't just taking in oxygen. We're getting rid of carbon dioxide and other waste products too.

Takanori - Throughout the experiments. We are quite surprised to see that carbon dioxide is actually eliminated from the body. So this observation is supporting the idea that oxygen is sucked up into the circulatory system. And whereas carbon dioxide is eliminated from the body as if perfluorocarbon is working as a breathing or gas exchange in the rectrum regions.

Eva - Takanori imagines that this new technology could be life-saving if deployed in ambulances for people being rushed to hospital, unable to breathe, or in hospitals for COVID patients who require extra oxygen or where there are limited mechanical ventilators. And he's also been approached by some other characters.

Takanori - Yeah. We actually had a discussion with an astronaut yesterday, and he is really excited to apply to space applications, particularly in emergency conditions. So there are a number of potential scenarios. We can envision the application of the intestine breathing approach, not just for medicine, but also for more broader context. So that was really exciting to me

Eva - Who knows, perhaps in the future, you'll be scuba diving without a gas canister to lug around with you. And instead with a more subtle breathing apparatus to keep you going.