Summary of Key Points
Inspired by the natural phenomenon of animals such as turtles and dragonfly larvae “breathing through their hindquarters,” a Japanese research team first demonstrated through animal experiments that oxygen delivery via the intestines could alleviate symptoms of hypoxia. In 2025, the world’s first human clinical trial will be conducted to verify the safety and feasibility of administering a specific liquid (perfluoronaphthalane) directly into the intestines via the anus. This technology has the potential to become an adjunct or alternative to ventilators, providing a new option for patients with respiratory failure, especially in situations where ventilators are scarce and resources are limited.
1. Nature’s “Unique Abilities”: Animals That Breathe Through Their Hindquarters
Many animals have evolved the ability to breathe using their hindquarters:
- Owen’s shelled turtle: To avoid predators (since breathing at the surface makes them vulnerable to birds or crocodiles), it draws water through a cloacal opening near its tail, extracts oxygen from the water, and then breathes underwater.
- Dragonfly larvae: Even more ingenious—after drawing in water and oxygen through their intestines, they contract their anus to expel water, using the resulting thrust to move forward, allowing them to both breathe and escape or hunt.
- Loaches: Also use their hindquarters for breathing.
Scientists wondered if mammals could utilize the same method of oxygen absorption through the intestines and began conducting research.
2. Animal Experiments: From Laboratory to the “Ironic Nobel Prize”
The team conducted two rounds of experiments on mice and pigs:
- First round (using pure oxygen): They thinned the intestinal walls of the mice to increase oxygen absorption and then infused pure oxygen into their intestines, placing them in a hypoxic environment. Results showed that 75% of the mice in the thinned-intestine group survived for more than 50 minutes, compared to none in the control group.
- Second round (using an oxygen-rich liquid): They administered perfluoronaphthalane, which can carry large amounts of oxygen, into the intestines of hypoxic mice and pigs. The blood oxygen levels of the mice increased significantly, and they could walk distances eight times longer than those in the control group; after three administrations, the pigs’ blood oxygen levels rose by 15%, and symptoms of hypoxia (pale skin and cold limbs) were alleviated.
The research was published in 2021 and won the “Ironic Nobel Prize” that same year (due to its seemingly absurd nature but thought-provoking implications). The researchers initially had mixed feelings, but they were delighted to draw attention to this field and moved on to human trials.
3. The World’s First Human Trial: Is It Safe?
The 2025 human trial focused solely on assessing safety (the liquid contained no oxygen):
- Participants: 27 healthy Japanese men aged 20–45.
- Procedure: The perfluoronaphthalane was administered similarly to an enema, with doses ranging from 25 ml to 1500 ml, and participants were asked to hold their breath for 60 minutes.
- Results:
- Doses below 1000 ml were safe; 74% of the participants were able to hold their breath for the entire 60 minutes.
- Side effects included a sensation of needing to defecate, abdominal pain, or bloating (more pronounced with higher doses), which subsided after the liquid was expelled.
- Vital signs and liver/kidney functions remained normal, indicating no adverse reactions.
Conclusion: This method is safe, but its ability to deliver oxygen to the blood has not yet been confirmed.
4. Why This Technology Could Save Many Lives?
Patients with respiratory failure often rely on ventilators, which have several drawbacks:
- Damage to the lungs: Mechanical ventilation (especially intubation) can cause lung damage and increase the risk of thrombosis and bleeding.
- Resource shortages: During the COVID-19 pandemic, there were not enough ventilators available for all patients.
- Complexity of use: Ventilators require specialized equipment and trained personnel, making them difficult to access in remote areas.
The advantages of intestinal oxygen delivery include:
- Allowing the lungs to rest by reducing the burden on them;
- Simplicity of administration (similar to an enema), eliminating the need for complex equipment, making it suitable for resource-limited settings;
- Potential application in special populations, such as newborns with underdeveloped lungs, who could benefit from this method.
5. What’s Next?
While the technology has been proven safe, its effectiveness still needs to be confirmed:
- Effectiveness testing: The next step will involve adding oxygen to the liquid and measuring its ability to increase blood oxygen levels in healthy individuals.
- Expanding the trial population: Trials will include women, elderly patients, and those with respiratory failure to observe different responses.
- Clinical application: If proven effective, this method could be used to treat patients with respiratory failure caused by conditions like COVID-19 or pneumonia.
This seemingly absurd concept of “breathing through the hindquarters” could become a lifesaver in times of crisis.