Can someone with real medical competence tell me why this weird idea wouldn't work?

[eppur_se_muova]

This idea occurred to me a couple of years ago. It concerns the need for patients with lung damage, or fluid-filled lungs -- such as pneumonia patients or victims of smoke inhalation -- to maintain blood oxygenation, when the normal process of O2 absorption from their lungs is frustrated. I suppose someone, at some point, might have tried using a heart-lung machine to bypass the lungs in desperate cases, but I don't know for sure. With heart-lung machines being more complicated, more expensive, and less common than ventilators anyway, this wouldn't seem to be much help in the COVID crisis, so something simpler is needed. Unfortunately, I'm not a doctor, nor any sort of medical expert, myself, and I don't know who I could recommend this idea to for possible evaluation.

The idea comes from one very odd observation. Some turtles -- air-breathing animals which totally lack gills -- are able to survive hibernation underwater for months at a time. Of course, this is partly due to a drastic slowing of the animals' metabolism, a common ability among reptiles, but it's not enough by itself. Recently, investigators learned that these turtles are actually capable of "breathing" underwater -- through their butts. Now, technically, it involves the cloaca, an organ found in reptiles and birds, but not humans. Now, I realize turtles are not humans, and (with one prominent exception) humans are not turtles, and a human intestine is not the same as a cloaca. But consider what the intestines do -- they absorb nutrients, water, and salts from the contents of the digestive tract (water and salts apparently flowing both ways, as needed), at least partly by simple diffusion. To make this process rapid enough to be effective, the inner surfaces of the intestines are covered with tiny protrusions called villi, which increase the surface area available for diffusion, complementary to the way the airways of the lungs are ramified into many tiny alveoli for rapid diffusion of O2 and CO2. So couldn't an intestine serve as an alternative lung ? This is an idea which could be quickly be tested on dogs or pigs -- use a colonoscope or similar device to insert a tube deep into the colon, pass in O2-enriched air and allow it to pass out again through the anus. Then cut the animal's O2 supply (substitute pure N2, e.g.) and monitor the blood oxygen level. Even if this method is not as effective as normal breathing, it could still be very useful. It probably couldn't substitute completely for a ventilator, but might substantially augment oxygenation for patients in extreme pulmonary distress -- maybe enough to tip the balance. The equipment involved is not much more complicated than the high-flow nasal cannulas commonly in use, and much simpler than a ventilator. When ventilators run out, maybe it could even serve as a stopgap until a ventilator becomes available.

Again, I'm not a doctor, and don't have any in the family or my circle of acquaintances to discuss this with, but I'm just putting this out there to see if anyone can find merit in it, or improve the idea to the point it's more worth considering. Hope it helps someone, somewhere, somewhen.




(Possible later development -- use silicone or fluorocarbon fluids -- artificial blood -- in place of air. Might be of interest for deep-sea diving, or at least SF stories about same.)

[mr_lebowski]

1. So ... blow smoke up their ass?

[Captain Zero]

7. which was used with drowning victims at one time and thought to resuscitate them

same concept, but I don't think it worked so well with smoke maybe pure O2 though?

BECAUSE, a pneumonia patient is drowning.

[mr_lebowski]

10. I had to say smoke for the joke to work ;)

I know it would be oxygen IRL ...

[The Velveteen Ocelot]

2. Trump talks out his ass, so I suppose it's theoretically possible

to breathe through one's asshole as well. At least he might be able to do it.

[Sogo]

3. A colonoscopy requires

days of preparation, i.e., clearing of the colon so that whatever is put up the anus isn't obstructed or doesn't act as a suppository/enema. I doubt a COVID-19 patient in need of a ventilator could go through the rigors of that cleanse, for one thing....

[PoindexterOglethorpe]

4. You are looking at animals that evolved to do what you are talking about.

Humans have not.

[Buckeye_Democrat]

5. Shared blood seems easier to me, but...

... I doubt that connecting two people so their blood (same blood type) is always shared would ever happen.

Lab animals like mice have been surgically connected in that way.

I have a rare genetic condition that causes blindness (my two oldest siblings are blind and I’m blind in one eye so far). It’s an ancient gene found in all mammals, and even fish.

Mice with the same genetic condition have been created by “knocking out” the same gene in the mice eggs and sperm and allowing fertilization. (It a recessive condition, so both copies of the gene need to be defective to cause problems.)

Despite the gene being identified, it’s STILL not understood what it does. It’s mostly active in the liver, though, and it apparently transports “something” out of the bloodstream or into the bloodstream.

Anyway, mice with the genetic condition have been surgically connected to share their blood with normal mice. When that’s done (the blood is constantly shared), none of the mice develop blindness.

Edit: Shared blood in the uterus might also explain how mammals are born “normal” with this condition and develop problems later. Fish with the condition, on the other hand, don’t survive to hatch. Their bones are a twisted mess during development in the egg. (Blindness is the result of bone-like mineralizations that happen in a membrane behind the retinas.)

[Laffy Kat]

6. Well, they do use ECMO on sepsis patients at times.

Isn't that essentially doing the same thing? It's less invasive and more portable than a heart-lung machine. I'm not sure how long someone can stay on ECMO, however.

[safeinOhio]

8. I'm a little nuts my self,

but some times those voices in my head have some great ideas. Nothing wrong with thinking outside the box.
Those voices in my head are telling me this, may be a great post.

[GaYellowDawg]

9. I don't think it would work.

There are a couple of main reasons I don't think that would work.

1. Too thick a layer to allow diffusion of oxygen into the bloodstream, I think. We're reliant on hemoglobin because oxygen doesn't dissolve into water very easily, especially at our body temperature. In order to load oxygen onto red blood cells, the oxygen molecules have to pass through alveolar cells, which are very thin (a type of tissue called simple squamous epithelium), then a thin protein basement membrane below it, then the walls of the alveolar capillaries, then across the red blood cell membrane. Only then is O2 loaded onto hemoglobin.

In the large intestine, the oxygen would have to pass through a mucus layer much thicker than that in the lungs. Then the cells themselves are much thicker - simple columnar cells. They are, as the name implies, column-shaped instead of flat. Then after the columnar epithelium, the O2 would have to pass through a protein basement membrane, then through a thin layer of smooth muscle called the muscularis mucosae, then through at least a little connective tissue to make it into the capillaries in the submucosa. It's unlikely you'd be able to put the oxygen at a high enough partial pressure to drive it into those capillaries.

2. The hemoglobin would probably have less affinity for oxygen. In the lungs, the local environment is more alkaline than in peripheral tissues. This pH causes hemoglobin to adopt a form that has a higher affinity for oxygen, and it's easier to load the O2 onto hemoglobin. Out at peripheral tissues, where cellular respiration is producing a lot more CO2, the local environment is more acidic. That pH causes hemoglobin to adopt a form that has a lower affinity for oxygen, and in that case, it's easier to unload oxygen and more difficult to load oxygen than it is in the alveolar capillaries.

The diffusion distance and pH, I think, would prevent this from working well enough to make a difference. It's not bad thinking, though, and I would love to field a question like that from my students.