How to increase the efficiency of lungs

Question

Humans (and mammals) have 2 lungs, one right and the another left. The right lung has 3 lobes and the left have 2 lobes because in the "third" there is the heart, so the right lung is bigger than the left.
I want to make a race with two hearts so I have to remove one lobe of the right lung to locate the heart and also I have to move a little the left heart.
If I remove a lobe this race would have a less pulmonary capacity and won't be able to run much. How can I overcome this problem?

My ideas are:

• Increase the size of the lungs: The problem is that I don't know if we have "free space" in our body to do that.
• Hollow bones: Some time ago I read that birds have hollow bones and they store air inside to breath later, then I found that is false but it is still an interesting idea. The problem with that is I would make bones less strong and I don't want that.
• Increase efficiency: I couldn't find any page with this information but 2 years ago I read that we inspire air with 21% O₂ and exhale with ~15% O₂, so we breathe the ~6% of O₂ in air. Maybe it's possible to increase this efficiency and exhale air with 10% O₂ or less to compensate for the lost lobe. The problem again is that I don't know if that it's possible or how to do that.
• EDIT ADDED:
  • Myoglobin: searching more about the ZioBite's answer I found the myoglobin, a substance similar to hemoglobin but instead of transport oxygen it's used to store oxygen in the muscles. This could explain how they can do physical effort but not how they live normally (because this store slowly the excess of oxygen not increase the oxygen input).

I had some ideas but I don't know if they are possible or how to do them.

Answer 1

The way birds do it.

The air passes one-way through the lung and can extract nearly all the oxygen in one pass.

A diagrammatic representation of the cross-current respiratory gas exchanger in the lungs of birds. Air is forced from the air sacs unidirectionally (from right to left in the diagram) through the parabronchi. The pulmonary capillaries surround the parabronchi in the manner shown (blood flowing from below the parabronchus to above it in the diagram). Blood or air with a high oxygen content is shown in red; oxygen-poor air or blood is shown in various shades of purple-blue.

Answer 2

Exit route

Imagine a car parking lot with one single lane entrance. You can either admit a car or allow a car to exit. If you have high volume you can admit a bunch of cars at once, then allow a bunch of cars to exit.

Now you open another lane. Cars can exit all the time, and enter all the time. You can have a steady stream of each. It is more efficient because you never need to stop and reverse traffic.

Do the same with the lung. Open an exit route. This will be a hole somewhere in the bottom of the lung (which might be better configured more like an intestine with this scheme - a air-filled tube rich with alveoli). I envision this right around the xiphoid. Oxygen rich air enters continuously at the entrance and exits continuously at the exit. The mechanics of breathing will be different and might be more like our digestive tract, another system with an entry and exit. The digestive tract operates using peristaltic waves and I can imagine a respiratory tract with an entrance and exit doing the same - perhaps with many small valved chambers along the way which open and close in sequence.

I here assert you will double efficiency by not having to regularly reverse flow.

Answer 3

One of the quickest ways to increase the efficiency of the cardio-vascular system is to take EPO/use blood doping. So, it seems the lungs and heart are already big enough to utilise more oxygen carrying capacity than our blood already has. You ought to be looking at increasing the efficiency of the blood. The more oxygen your blood can carry, the more of it will be extracted from the air in the lungs. And the more oxygen in the blood, the more oxygen your heart will pump to your muscles without needing to change the amount of blood being pumped.

See here, from the 90s onward: Tour de France

In short, make the blood better - not the organs.

Answer 4

A few points:

• Having hollow bones doesn't make bird bones more fragile, it makes them lighter (and you need some other place to to put the "factory" of erythrocyte, but that is another matter). A pipe is much stronger than a bar of same weight and material.
• If You need a more efficient respiratory system copy cetacean system. They can store oxygen in muscle tissue and exchange very efficiently with a single breathing act (see, for example).
• In general the rib-cage size is not a real constraint, lung status is: a "normal" human being has a "vital capacity" (volume difference between full and empty lungs) averaging around 5 liters, but normal respiration uses about 3 liters (or less) and athletes can move more than 7 liters in a single respiratory act. Severely handicapped lungs (such as those of long time heavy smokers) can have "vital capacity" lower than one liter and people still survive with only "marginal drawbacks" (i.e.: use a lift instead of stairs ;) )

Answer 5

It seems like you don't want to change human physiology much so the easiest things to do would be to increase the efficiency of the bodies. As you said we only absorb 6% of the oxygen we breathe in, so let's find the bottlenecks.

Potential bottlenecks are:

• Airways - The amount of air we can breathe in.
• Blood - The amount of air our blood can absorb.
• Lungs - The amount of air our lungs can put into our blood.
• Body - The amount of air our bodies need to function.

Improve Airways

While the first is the least likely, it's obvious that we breathe faster or deeper when we're in a state where we need more air. A solution would be faster or bigger airways (we also tend to use our mouth for breathing instead of our tiny nostrils). Another issue we face is that we can not breathe in and out at the same time reducing the potential efficiency by 50%. Others here have identified this and claimed that it would work if you had an entry and exit hole, but keep in mind that air needs to flow in and out continuously as well. That would only work with a 2 chambered valve system similar to a heart.

Improve Blood

All of this is meaningless if our blood can not absorb enough oxygen. Since extreme divers hyperventilate before a dive to fill their blood with more oxygen, it seems like this is not the case - on the other hand, athletes try this angle when doping. Some of the things they do that increase the amount of oxygen that can be carried by our blood are to increase the number of red blood cells. I assume some other elements might be more efficient in carrying oxygen. This can also change the color of blood, Crustaceans, for example, have copper based blue blood rather than iron based red blood.

Improve Lungs

As I said, divers hyperventilate to increase the oxygen in their blood. This implies that the bottleneck is the lung. While you suggest that the size of the lung has to increase, this is actually not the case. What's more important is to increase the surface area of the lung. Their lungs could be built like window blinds, like a CPU cooler/heat sink with fins, or similar to fishes gills, which are made for breathing in low oxygen environments. The last two options would work best with flowing air, similar to first suggestions. Since your humans are double hearted and their blood would flow faster, chances are this will become an even higher bottleneck than it already is.

Improve Bodies

Our bodies can become more efficient and require less air to perform the same way. If you've ever tried to get in shape, you might have noticed that at first, you'll be out of breath after a short run. However, once you've trained for a while, you can run for a while until you finally run out of breath. Your double hearted humans could have a better physique anyway and thus not be out of breath as fast.

Answer 6

Consider the biochemistry of this race

Above answers are all very good! However, although this doesn't specifically apply to the lungs, you could also consider the molecules that are involved in oxygen transport. This works if you were looking for an option that involves biochemistry, rather than further changing the anatomy of your new race. To do this, you may wish to consider the protein hemoglobin, which binds oxygen and then transports it to cells. As you have mentioned, myoglobin is another important protein, and is a key player in diving mammals, though I believe the molecules that allosterically bind to hemoglobin are a better option.

In particular, a real life applicable example is 2,3-bisphosphoglycerate (2,3-BPG). This is the molecule that leads to populations that live in higher altitudes being more efficient at transporting oxygen. In short, this molecule decreases the oxygen affinity of hemoglobin, meaning it is released more easily when it reaches the cells. Since oxygen itself is an allosteric regulator of hemoglobin, as more oxygen is released from the one hemoglobin protein, more will want to be released as well! Populations at sea level have around 5mM concentrations in their blood, whereas populations in higher altitudes can have around 8mM concentrations.

You may also wish to do some research on the other molecules that are involved in hemoglobin regulation, such as hydrogen protons and carbon dioxide (the acidity of our blood near our muscles is higher than at the lungs, and this results in oxygen unbinding from hemoglobin so it can be used by our cells).

In conclusion: this is probably something that you might wish to 'add-on' to one of the other options provided, as there is a limit to how much you can play around with the levels of these molecules in our blood. If you were to increase the concentration of BPG tenfold, then oxygen would never even bind at the lung-blood barrier!

Just a few questions Is this really just a different race of humans? If you are trying to ground your creation in reality, have definitely considered the plausibility of having a different race of humans with two hearts. Can they mate with one-hearted humans? What would the result be? Could this in fact be another species, closely related to humans?

EDIT Here is a graph that shows the binding of oxygen to hemoglobin vs the partial pressure of oxygen for blood with and without BPG. Though this may be hard to understand without having being taught it, there are many resources explaining the role of BPG in the blood.

Also note that it would not be too far-fetched to perhaps say that the hemoglobin in your new race has changed in such a manner that it is more efficient at transporting oxygen. In hindsight, I definitely think that that is probably the best option to go with if you don't want to have to change the anatomy of your new race any more than the extra heart!

Answer 7

To add a little to the 'yoga breathing' line of thinking, with a view to the underlying physical mechanics:

If, say, 2 litres of air goes into your lungs, then necessarily 2 litres of the volume of the rest of your body, needs to be displaced, somehow, somewhere. There is a certain degree of flexibility in how to do this, and some ways are better than others, and some ways easier to learn than others. The former tend to turn up in practices which deliberately teach breathing, the latter turn up as people's typical breathing habits.

Now if our 2 litres of body-volume immediately surrounding the lungs has to move out to allow the lungs to expand, then 2 litres of body volume surrounding that has to go somewhere. And so it continues from the lungs themselves to the extremities of the body, or at least until this 'one bit of the body making way for another' ceases.

Now of course the physical work done to get the air in the lungs is, technically, done by the pressure of the air outside your body pushing the air in, due to a decrease in pressure in the lungs, caused by the volume of the lungs expanding. To breathe in, the body must thus work to increase the volume of the lungs. Part of doing this physical action efficiently, from an engineering perspective, is distributing the workload around the body. Another part is minimising mechanical losses due to one part of the body unnecessarily working against the efforts of another. The other is doing this so that you get an optimal amount of air in and out for the amount of oxygen your body needs.

When you hear yoga (and perhaps tai chi) teachers giving the seemingly crazy instruction to 'breath into your feet' or something like that, what is being got at is, in some sense, this 'mechanically efficient' breathing described above. But to actually do this, it is necessary to understand how to do it in terms of body sensations, and instructions the brain can deliberately give to the muscles, hence the very subjective viewpoint. If you actually do this, (to my experience,) it can feel as if you are breathing into your entire body, and to actually deliberately do this, you breathe as if you feel you are breathing into your entire body. (With years of practice, the deliberate stuff gradually becomes instinctive and automatic, of course, which is why the word 'deliberate' is important here.)

Much of yoga and tai chi is described in terms of how things seem when you are doing them correctly, rather than in terms that an engineer or biomechanics specialist would think of when understanding and explaining things (since they are generally talking about a body other than their own, whereas the yoga and tai chi practices are largely about teaching you about what you do with your body and your mind).

But to conclude, if you think about the mechanics involved with breathing, given a pre-existing piece of breathing apparatus (so you can't swap e.g. human lungs for bird lungs), thinking like the above can arise quite readily, and from there the connections to things like yoga and tai chi start to become apparent.

Answer 8

One specific idea - separate breathing from eating.

As humans we have to stop breathing for a moment to drink or swallow. Evolutionarily-speaking, its probably to make the best use of a complex system of the mouth for speaking as well as chewing rather than duplicating things.

If the beings had separate eating orifaces from their breathing ones, then efficiency rises and multitasking becomes more possible.

Downside, the human nose depends on air movement to smell things, and having no air movement there would impact on the sense of taste.

On the positive side, there's zero danger of choking on food, or inhaling vomit into the lungs because of the partitioning of systems.

Answer 9

To increase the efficiency of the lungs try breathing using your diaphragm. Commonly called Yoga breathing, you intake by pushing your stomach muscles out to fill your lungs. This generally increases lung capacity by 20–25% intake.

Hold longer to pass more oxygen through your blood, exhale slowly.