By Linda Hasco
The coronavirus pandemic has highlighted the importance of mechanical ventilators as life-saving tools. But what happens when those tools are not available, or the supply runs out?
Japanese scientists have studied a new method of delivering oxygen to mammals that one day may be used on humans.
The New York Times reported that Dr. Caleb Kelly, a gastroenterology fellow at Yale University, laughed when he was recently asked to review a paper about the administering of lifesaving oxygen to mammals through their anuses, thinking it was a joke.
However, the authors of a new study, published Friday in the journal Med, are perfectly serious. The study showed that some mice or pigs when dangerously deprived of air, can be rescued with an enema of oxygen-carrying liquid. And, Dr. Kelly said in a commentary he wrote accompanying the new paper, “It actually turns out it could be a feasible approach.”
What motivated the study?
His father’s battle with lung disease motived Dr. Takanori Takebe, of the Tokyo Medical and Dental University and the Cincinnati Children’s Hospital Medical Center, to examine the unusual idea. While mechanical ventilators can keep patients alive when their lungs are failing, as the COVID-19 pandemic has shown, they aren’t always available, or supplies can run out.
Dr. Takebe said that studying the idea in human patients may be down the road a ways, but noted that there is a clear need for different strategies to help patients with severe lung failure.
The report said that Dr. Takebe’s original research had focused on growing miniature organs such as lungs using stem cells in dishes, but evolved into something totally different: the repurposing of mammals’ existing organs.
The study noted that Dr. Takebe was inspired by members of the animal kingdom, upon learning that many fish and other creatures have multitasking organs. An example being a fish called loaches, which typically use their gills to take oxygen from the water. When water oxygen levels get severely low, they can also pop their heads above the surface for a gulp of air, which travels through their digestive tract where the oxygen is absorbed by their intestines.
In the study, Dr. Takebe and his co-authors set out to determine whether a mammal’s intestines could also absorb oxygen. Using anesthetized, oxygen-deprived mice, researchers pumped oxygen gas up the mice’s rectums. The procedure did help the mice survive longer, but was most effective when researchers scraped the intestinal wall to thin it, a method “not very appealing for treating sick human patients.”
However, the study found that when scientists tried delivering oxygen in liquid form by squirting the oxygen-packed liquid into the rectums of mice and pigs dangerously deprived of oxygen, blood oxygen levels were boosted to the point where the mice started walking around again. The pale skin of the anesthetized pigs turned a healthy pink.
How successful was the experiment?
Dr. Takebe said the procedure worked better than he had expected, noting that the animals were completely recovering from the very, very severe hypoxia. He said. “That was really astonishing to me.”
Although a mammal’s colon is not used for breathing, the thin-walled organ is proficient at filtering substances into the body. “What separates the environment from inside the body is a single layer of cells,” Dr. Kelly said.
The report cited Dr. Kelly, who noted that while the concept is “fascinating,” he questions whether it’s “ready for prime time” yet. “It’s kind of a startling idea, to use that part of human anatomy for gas exchange,” he said.
Still, he added, “the weirdness doesn’t mean we should dismiss it.”