EPV update 2020.04.25
Sorry for the lag in updates, a lot going on on the development side and not so much time for web page editing. The valving and control system has been completely updated, I don't have time to post the details right this minute but we're trying to pull that together into something more coherent this week.
The most recent performance data was captured on a full-size chamber (half-barrel and poly "poncho"), using the revised regulator designs and powered by an older central vac system. I switched to using that as it is a) quieter than my big shop vac; and b) a weaker system, and I wanted to make sure it works without requiring a particularly powerful system. Timing at this point is entirely manual, but I am hoping to connect the automated timing system shortly.
Here are some slow cycles in the system, you can see the pressure regulator is hitting the target pressure very rapidly, and then holding it stably.
There is almost no lag between the sensor immediately at the regulator, and the one inside the patient chamber.
This is a bit slow for breathing though, so here is a faster series
And then even faster
This is still with me throwing the main plateau / PEEP switching valve manually for the moment; also there was a leak in that main switching valve I was plugging with my hand, hence some of the variability (I'm going to rebuild it so no point in fixing that right now). But at this point we're up over 30 bpm, with a full-range transition that will exceed the most likely use-cases - the current PPV standard includes PEEP (which will be incorporated here as well, just left out for simplicity in component testing at the moment), and so the per-cycle transition would be a more moderate one (e.g. -15 cm H2O to -30 cm H2O).
So at this point I am confident we can achieve the technical requirements, now on to integrating the control system and some more substantial testing.