There is a narrow range of pressure where you're not damaging the alveoli from underpressure, but not bursting the lungs from overpressure. You need a mechanical scalpel, not a butcher's knife.
Honest question: is the pressure range actually that narrow?
People can survive at high altitudes, which will see pressure of 70% sea level (or less, especially when considering mountain climbing). Additionally, when SCUBA diving, something like 30 feet of depth = 1 atmosphere.
I feel like I'm missing something here. Any ideas?
Covid patients in the ICU probably don’t have healthy lungs. The people you’re talking about at those pressure ranges are probably all young, healthy and athletic.
I know a bit about scuba diving, and you absolutely are not supposed to go diving if you have a lung injury.
I would speculate that if you put a person with serious covid on a mountain top or 30 meters under the ocean it would kill them pretty quickly..
As you point out, the body can tolerate significant variation in absolute pressure, corresponding to the temperature, composition, and density of the gas you breathe.
The pressure that must be narrowly controlled in a ventilator application is the relative pressure: the difference between the absolute pressure outside the lung (in the room) and the absolute pressure inside the lung. This relative pressure is what does all the work --- mechanically opening airways and alveoli --- and could cause all the injury.
Scuba divers are at ambient pressure and breathe through demand valve regulators. Pressures inside their lungs are almost exactly the same as outside so there's no extra stress.
Increasing pressure with depth does increase work of breathing due to higher gas viscosity. Beyond a certain depth, divers can no longer ventilate enough to take in O2 and remove CO2. This problem can be mitigated to an extent by breathing lower density gasses such as helium. Occasionally hospitals even have patients with severely impaired lung function breathe heliox just to get better gas flow.
In theory it's possible to use a 2nd-stage scuba regulator as an improvised mechanical ventilator by partially blocking the exhaust valve with your hand and pressing the purge button. In practice it's unlikely to work, but if I was trying to rescue someone who had stopped breathing in the water and had no way to get them back to shore or a boat quickly then I might try it as a last-ditch effort.
Yes, it's pretty narrow. I've had double pneumonia somewhere in my 20's. Just playing a reed instrument (sax) was over-pressuring my lungs to the point that it led to more damage over time. And that's only a tiny little bit of pressure.
What’s the limiting factor there? The pressure regulation, pressure production, measurement accuracy? There’s open source ECUs that measure dozens of sensors at 1000hz+ and keep an engine perfectly timed using a $35 raspberry pi. Is this problem harder somehow?
How could we archive that? its not like almost disposably cheap actuators moving with 0.1mm precision guaranteed for >10K hours MTBF was a solved problem over 30 years ago (floppy drive). /s
