http://www.lslbo.org/wp-content/uploads/2018/10/bird-lungs.j...
Note that sleeve piston engines like the Rolls Royce Crecy, are much more efficient than valves, but development stopped at the end of WW2 and resources focused on jet engines.
Rolls Royce Crecy - The Most Advanced Piston Aero Engine Never Made
https://www.youtube.com/watch?v=cxK_zWgw6gY
2) the exception to continuous flow is the WW2 V-1 pulsejet engine, which has a gate that is closed at combustion time, about 42 Hz.
The pulsejet is a very interesting engine in that it's the simplest possible jet engine - literally an empty metal tube with spray nozzles and a sparkplug.
The V-1 was the first mass-produced cruise missile. The Germans also had air-to-ground (anti-ship) guided missiles both wire-guided and radio-guided with a TV screen(!)
But the US Navy was the first to build precision-guided autonomous missiles, both the all-analog Sidewinder and Wall-eye, which shared modules. The Wall-eye made the famous Gulf War photos you've seen of entering via windows. It had analog circuitry to do edge-detection in real-time.
From my quick research just now, it seems continuous flow hearts are not better because they pump differently. That's just a side effect with no benefit that's noted in studies. A continuous pump is much smaller, and for long-term total heart replacement, is the only thing that can be small enough to fit in the body. In fact, it's noted in a case study that they're not sure about the long term effects of not having pulses, and that's something that will need to be studied.
Now as far as the lungs - I think that would be a bad idea too. We'd need separate flow-through pathways to inhale and exhale. So two necks, or an exit hole in the chest. That takes up space and is another vector for infection. In addition, exhaling moisturizes the tissue, so you'd need much harsher intake tubes, and your exhale tubes would be constantly dripping water. All that extra space has to come from somewhere - meaning you now have less space for actual oxygenating tissue, resulting in worse oxygen capture. Now the diaphragm has to pump harder, because you're not extracting as much oxygen from your air intake.
Anywise, you had a funny comment, which I hopefully made funnier by responding to it seriously. We're a good team. Team Heart & Lungs they call us.
He's on Twitter and a total medical/heart geek, I'm sure you could ask him and he'll probably provide you with references.
(Edited to add text in parenthesis in 3rd sentence)
Mammal: Inhale -> burn -> exhale
Bird: Inhale -> burn
-> inhale -> exhale
The bird mechanism is obviously efficient for oxygenation but it must have a cost that our body plan discarded or at least failed to even consider many millennia ago.
Our body plan didn't discard this mechanism, any more than it discarded wings or beans. We never had any of those features in our ancestry, because mammals aren't descended from birds. Our most recent common ancestor is much, much earlier than bird ancestors began evolving any mechanisms related to flight or high-altitude breathing.
You only climb mount improbable, you don’t go down it
Because their lungs are tied to their flight muscles, they would overbreath at cruising speed. So the long necks provide just the right amount of re-breathed CO2 to offset this.
(I hope I have this correct)