- According to a new report, rodents and pigs can breathe through their intestines.
- The researchers were able to reverse the effects of respiratory failure in mice and pigs by injecting oxygen gas or oxygenated liquid via the anus.
- The results may pave the way for new emergency treatments to help critically ill patients when mechanical ventilation is inaccessible or ineffective.
- The researchers plan to continue their study and look into the clinical application of this method in humans.
According to a new review, rats and pigs can effectively breathe through their intestines.
By supplying oxygen via the rectum, the researchers were able to save pigs and mice from respiratory failure.
These results could pave the way for new treatments to keep the body oxygenated when the lungs fail and mechanical ventilation is not an option.
Dr. Takanori Takebe, a senior study author who works at the Tokyo Medical and Dental University and the Cincinnati Children’s Hospital Medical Center, says, “Artificial respiratory support plays a critical role in the clinical management of respiratory failure due to serious illnesses such as pneumonia or acute respiratory distress syndrome.”
“Although the side effects and protection must be carefully tested in humans,” Dr. Takebe continues, “our approach can provide a new model for supporting critically ill patients with respiratory failure.”
The research was published in the journal Med.
Intestinal breathing in the animal kingdom
Several marine species have evolved alternate breathing systems in addition to lungs or gills to live in low oxygen conditions. Loaches, sea cucumbers, some freshwater catfish, and stretch spiders, for example, all breathe from their lower intestines.
However, whether mammals have similar abilities has remained a mystery up to now.
Dr. Takebe told Medical News Today, “This is [the] first [study] to our knowledge to demonstrate effective repurposing of the distal gut for breathing apparatus inspired by aquatic animals.” “We are all shocked that the loaches’ intestinal breathing ability is preserved in mammalian organisms to the point where it is adequate for saving [from] lethal hypoxia/asphyxia conditions.”
Respiratory rescue
Dr. Takebe and his colleagues used pig and rodent animal models to show that mammals can breathe through their intestines.
To begin, they created an intestinal gas ventilation system that delivered pure oxygen gas to mice’s rectum in an enema-like procedure.
The mice were then subjected to extremely low oxygen levels. None of the animals lived for more than 11 minutes without the intestinal ventilation system. The mice’s median survival time was increased to 18 minutes by administering oxygen gas via the anus.
The mechanism worked best when researchers made a slight abrasion in the mucous membrane of the intestine. Gas was able to travel more efficiently between the intestine and adjacent blood vessels as a result of the abrasion. In conditions that would usually be fatal, 75 percent of mice with intestinal abrasion and gas ventilation lived for 50 minutes.
Gas vs. liquid
Since the intestinal gas ventilation system necessitates the destruction of the intestinal mucosa, it is unlikely to be suitable for clinical use in humans, particularly in the most seriously ill.
As a result, the researchers devised an alternative procedure that employs an oxygenated liquid known as perfluorodecalin (PFD) and does not necessitate abrasion of the intestinal mucus layer.
PFD is part of a class of chemicals known as perfluorochemicals, which have been shown to be clinically safe in humans in studies. PFD has a particularly high oxygen and carbon dioxide adsorption potential, and recent clinical trials have investigated the use of perfluorochemicals as a blood substitute.
The mice in the research group were able to walk considerably further than those in the control group after receiving intestinal liquid ventilation, and more oxygen entered their cores.
The researchers have tried repeatedly injecting PFD into pigs’ intestines. They discovered that the treated animals had higher oxygen levels than the control animals. In addition, the medication alleviated the effects of skin pallor and coldness caused by a lack of oxygen.
Human clinical translation
In two mammalian species, the study demonstrates an important mechanism for circulating oxygen and relieving symptoms of respiratory failure.
The researchers’ next move, according to Dr. Takebe, is to extend their studies to assess mid-to-long-term safety before moving forwards with human clinical trials.
According to Dr. Caleb Kelly, a clinical fellow at Yale School of Medicine in New Haven, CT, who was not involved in the research, there might be a few bumps in the lane.
“[The] initial understanding of [intestinal ventilation] is likely to mirror that of faecal microbiota transplant […], which was considered untenable not long ago for ‘practical and cosmetic reasons,’ but now has less stigma as evidence supporting efficacy is overwhelming,” writes Dr. Kelly in a separate perspective article published in Med.
Researchers assume that if intestinal ventilation can transcend its stigma, it could one day be used as an alternative to artificial respiratory support for critically ill patients.
According to Dr. Kelly, mechanical ventilation is sufficient for delivering oxygen and removing carbon dioxide from circulation in the majority of patients. “However, mechanical ventilation may not be possible in certain circumstances encountered by first responders. Additionally, the latest pandemic has shown that mechanical ventilators are a limited resource.”
Dr. Takebe acknowledged that COVID-19 has shown the need for new life support technologies, but he cautioned that his team “must carefully assess the process’s protection, as COVID-19 has a very complicated pathogenesis.”
Prof. Michael Steiner, a consulting respiratory physician at the University of Leicester in the United Kingdom, was also contacted by MNT. Prof. Steiner responded, “Very small” when we asked how important these results are to the current COVID-19 pandemic and the resulting need for ventilators. This is preliminary analysis. [The findings] won’t apply to the latest pandemic, and it’s unclear if they’ll prove to be a successful strategy.”
The study’s senior author, on the other hand, is upbeat about the findings’ utility and relevance:
“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. 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 lifesaving oxygenation.”
– Dr. Takanori Takebe
