The Future of Respiratory Support May Be Through the Intestines

By Mike Howie

An uncommon fact about the everyday act of respiration is that, in some creatures, it can be done through their rear end.

Several aquatic organisms that live in low-oxygen environments evolved to breathe using organs other than their gills or lungs — namely, their intestines. This has been documented in sea cucumbers, loaches, and certain freshwater catfish. But scientists have debated whether mammals have similar abilities.

Now, researchers have demonstrated that rats, mice, and pigs can indeed “breathe” to some degree through their intestines. Their study, published May 14, 2021, in the journal Med, detailed how delivering oxygen gas or oxygenated liquid through the rectum saved two mammalian models from respiratory failure.

Take a Deep Breath

The study began with mice. The researchers designed an intestinal gas ventilation system that could administer pure oxygen to the mice through their rectums. The system had a positive effect on 75% of the mice.

So the first test was a success — it showed that the system helped more oxygen reach the heart and provided rescue in the face of conditions that would normally spell peril. The problem, however, was that the system required abrasion of the intestinal mucosa, making it unlikely to be applicable to human patients, especially those who are severely ill.

Faced with this fact, the researchers developed a second system, one that uses oxygenated perfluorochemicals, which have already been shown to be safe in humans.

This new liquid-based ventilation system delivered similarly successful results when tested with mice and pigs exposed to low-oxygen conditions. Pigs connected to the system exhibited reversed skin pallor and coldness as well as increased oxygen levels without obvious side effects.

These successes prompted the researchers to ask a bigger question: could a version of these systems help manage respiratory failure in humans?

New Potential for Respiratory Support

“Artificial respiratory support plays a vital role in the clinical management of respiratory failure due to severe illnesses such as pneumonia or acute respiratory distress syndrome,” said senior study author Takanori Takebe of the Tokyo Medical and Dental University and the Cincinnati Children’s Hospital Medical Center. “Although the side effects and safety need to be thoroughly evaluated in humans, our approach may offer a new paradigm to support critically ill patients with respiratory failure.”

The COVID-19 pandemic demonstrated at devastating scale just how critical respiratory care is. With hospitals around the world overwhelmed, the global supply of ventilators and artificial lungs fell short, endangering patients. Had more options for respiratory support been available, the toll of the pandemic might have been lessened.

These new techniques for delivering oxygen to patients in need are still in their infancy, but Takebe is optimistic. “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.”