A series of experiments have revealed a surprising route for lifesaving oxygen in cases of lung failure: the anus. The new study, published last week in the journal Med, showed that pigs and mice can be saved from suffocation by an enema-like anal infusion of oxygenated fluid that gets absorbed through the walls of the intestines, reports Nicoletta Lanese for Live Science.
If it can be adapted for humans, the technique could offer a useful, if unorthodox, new way of delivering supplemental oxygen to patients with acute lung failure, and one that might have potential to help those suffering from severe cases of Covid-19.
"The recent SARS-CoV-2 pandemic is overwhelming the clinical need for ventilators and artificial lungs, resulting in a critical shortage of available devices, and endangering patients' lives worldwide," says Takanori Takebe, a gastroenterologist at Tokyo Medical and Dental University and the Cincinnati Children's Hospital Medical Center who co-authored the study, in a statement. "The level of arterial oxygenation provided by our ventilation system, if scaled for human application, is likely sufficient to treat patients with severe respiratory failure, potentially providing life-saving oxygenation."
Takebe’s research into repurposing organs not normally associated with breathing in mammals to take in oxygen was inspired by examples from the animal kingdom, reports Elizabeth Preston for the New York Times. Freshwater fish called loaches, for example, can survive in low-oxygen waters by gulping air at the surface despite lacking lungs. Instead of lungs, the loaches pipe the air through their guts where their intestines can absorb the oxygen, according to the Times.
To find out if the same principle might work in mammals, Takebe and his co-authors tried several methods of pumping extra oxygen through the anuses of pigs and mice, reports Nikk Ogasa for Science.
First, the team placed 11 mice in a low-oxygen environment and supplied some of them with pure oxygen gas through their anuses. The mice receiving intestinal ventilation survived longer than those that didn’t. Among intestinally-ventilated mice, those that survived longest also had their intestinal walls thinned before the experiments, suggesting the intestinal scrubbing improved oxygen absorption, per Science.
Since thinning the intestinal walls of future human patients would present an obvious logistical issue, the researchers tried something else. The second round of experiments delivered the oxygen in a liquid called perfluorodecalin that can be super-saturated with oxygen, according to Live Science.
This technique seemed to work even better, and kept both mice and pigs alive by providing an infusion of oxygen through their rectums.
“They are completely recovering from very, very severe hypoxia,” Takebe tells the Times. “That was really astonishing to me.”
The process takes advantage of the thin walls of the intestines, which absorb nutrients from food and medications delivered in the form of suppositories.
But translating the technique for human use will likely take some time. Per Live Science, sending lots of oxygen through the back end of the gut could kill off important microbes that live there and that are only able to survive in a low-oxygen environment. As such, getting the treatment ready for people will require figuring out how many anal oxygen infusions a patient can receive without damaging their intestinal flora.
But Takebe is eager to surmount these challenges and bring the novel method to bear on critically ill human patients and has launched a start-up in Japan called EVA Therapeutics, according to the Times. (EVA stands for enteral ventilation via anus, the technique’s technical name). Takebe hopes to begin clinical trials as soon as next year.