Loaches and some other aquatic animals breathe through their intestines when the water runs short of oxygen. Whether a mammalian gut could be pressed into the same service has been genuinely controversial. So one group tested two versions in animal models of respiratory failure: oxygen gas delivered into the rectum, and an oxygenated liquid. Mice and pigs first, then safety work in rats. Did any oxygen reach the circulation?
Both routes rescued the animals. Intra-rectal oxygen gas and oxygenated liquid each provided vital rescue in experimental respiratory failure, improving survival, behavior and systemic oxygen levels in mouse and pig models. Rodent and porcine studies found the enema-like liquid procedure tolerable and repeatable, with no major signs of complications. The authors note that perfluorochemicals already have an established safety record in clinical use.
Several aquatic organisms, loaches among them, have evolved intestinal breathing to survive in water with little oxygen. Whether could be adapted to a mammal, using the gut as an additional site for gas exchange, has been highly controversial. The appeal is obvious: a route to the bloodstream that bypasses the lungs entirely.
Two modes were tested in an experimental model of respiratory failure. One delivered oxygen gas into the rectum directly. The other used liquid ventilation with oxygenated perfluorocarbon, an inert fluid that carries a great deal of dissolved oxygen and already has a clinical safety record.
After inducing , the team analyzed both approaches in mouse and pig, then ran in rat. Both intra-rectal oxygen gas and oxygenated liquid delivery provided vital rescue, improving survival, behavior and systemic oxygen levels.
The rodent and porcine work confirmed that the enema-like liquid procedure was tolerable and repeatable, with no major signs of complications. The authors propose it as a potential adjunctive means of oxygenation for patients in respiratory distress, which is the right framing for a result in three species of animal. No human has been treated this way here, and preclinical safety is the first step of a long road rather than evidence of clinical benefit.
wat. Oxygen delivered into the rectum reached the bloodstream and kept animals in respiratory failure alive, in mice and in pigs.
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Mechanical ventilation is scarce, invasive and sometimes insufficient. A route that oxygenates the blood without touching the airway would be an adjunct rather than a replacement, and the pandemic made the shortage concrete.
How do we know?
Okabe and colleagues induced type 1 respiratory failure in animal models, then tested intra-rectal oxygen gas ventilation and liquid ventilation with oxygenated perfluorocarbon in mouse and pig, followed by preclinical safety analysis in rat.
What is still unknown
Mice, pigs and rats. Nothing here is a human result, and preclinical safety in rodents is the beginning of a path to the clinic rather than evidence that it works in a patient.
Learn something?
Where to next
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