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Scientists are investigating whether mammals can breathe through the rectum - 12/20/2021 - Science

Scientists are investigating whether mammals can breathe through the rectum – 12/20/2021 – Science

Platonic clichés say that necessity is the mother of invention, but in the case of the Japanese scholar Takanori Takibe, it is more correct to talk about fatherhood.

His father was sick with a lung infection and needed intubation, and given the grave dangers mechanical ventilation could cause to the lungs, the son pleaded with the unusual: What if mammals, like some fish, could breathe through the rectum?

“Fortunately, he survived,” he said, “but when I saw that it was just luck, I began to think urgently of alternative forms of breathing.” Leaf A gastroenterologist, he is a professor at Cincinnati Children’s Hospital Medical Center (USA) and at Tokyo Medical and Dental University, a Japanese institution that pioneered this research.

Mechanical ventilation is used in patients with respiratory failure, such as those with severe cases of Covid, or those undergoing major procedures, an invasive procedure that can lead to numerous complications.

The most common are pneumonia and pulmonary shock, but heart and circulatory complications can also occur, according to Marcelo Alcantara Holland, a pulmonologist with the Intensive Care Committee of the Brazilian Society of Lung and Tuberculosis Medicine and one of the creators of Elmo, an assistive breathing helmet that has been used successfully on Covid-19 patients. in Ciara.

In this moment of pain, Takebe’s curiosity entered the picture. The researcher noted that aquatic animals, such as the American catfish and sea spider, have intestinal respiration mechanisms to survive under hypoxia, a state of hypoxia.

Then the scientist joined a large team to see if the mechanism could also work in mammals. Experiments with rats, mice, and pigs included depriving the animals of oxygen and testing various forms of anal insertion.

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In the first experiment, gaseous oxygen was used, which achieves the best results if combined with scraping the rectal mucus, but the alternative was abandoned: this practice can be harmful to the digestive system.

When the intestinal mucosa is intact, it acts as a barrier that blocks the passage of certain substances as well as microorganisms, explain brothers proctologist Bruno and Marcelo Giusti and Wernick Cortes, president and marketing director respectively for Sociedade Mineira de Coloproctologia.

In other words, intentionally injuring the intestinal mucosa is not a risk-free procedure, since it loses its protective function against the passage of potentially harmful agents, such as bacteria and viruses, into the bloodstream and the whole organism.

In the second test, scientists on Takebe’s team used oxygenated PFC (perfluorocarbon), an oxygen-rich aqueous solution known to be versatile and compatible with the human body. The fluid is introduced through the rectum, facilitating gas exchange with the surface of the intestine.

In the control group, which did not have any kind of intervention, none of the animals survived for more than 11 minutes. In the group that received gaseous oxygen and mucus scraping, the survival rate was 75%, and the animals survived an average of 50 minutes in severe oxygen deprivation.

Animals given the PFC aqueous solution had similar results, and in both cases, there were no side effects — but the authors note that the potential long-term effects have not been studied.

Gas exchange in the intestine is possible only because the rectum in mammals contains a complex vascular network connected to the systemic circulation. This is nothing new: there are medications that are commonly taken rectally and are known for their rapid action.

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They can be used for topical action or in cases where the oral route is contraindicated, such as when the patient has irritation of the upper GI tract or when they are unable to swallow, for example.

Absorption of medications through the rectum can be very fast, depending on the formulation used, and it’s an important way to use medications in emergencies, such as seizures in children, say proctologists Marcello and Bruno Giusti.

However, it is important to know that the oxygenation technique is far from being applied in human therapies. Research needs to go through further stages, and clinical establishment can take up to a decade.

There is currently no ongoing research to study intestinal ventilation in humans. Takebe hopes it will be possible to start one in 2022 through the startup he founded, EVA Therapeutics Inc (EVA is an acronym for Trans-Anal Intestinal Ventilation).

“It is the first time the topic has been studied,” says the scientist, “but it is interesting to note that 400 years ago, a slightly similar method, although not the same, was used in traditional medical practices.”

Refers to a traditional North American Indian practice, the tobacco smoke enema. The method consists of blowing tobacco smoke into the anus of patients through a long tube. Initially, smoke was applied to revive and warm, especially to drowning victims.

With the colonization of North America, Europeans imported the technology and began to use it to meet the most diverse demands. There are reports of tobacco smoke enema being used for minor purposes, such as headaches, colds, and even hernias, typhoid, and cholera.

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However, this practice was not accepted in the 17th century, when British physician Benjamin Brody demonstrated the toxicity of nicotine.

Scientists who continue studies of intestinal ventilation will have many questions to answer and limitations to solve. It will be necessary to discover, for example, how to reconcile the use of the rectum for respiration with the physiological needs of the digestive system, such as the evacuation itself.