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PID Controller Design for Ventilator

Started by Ricketty C August 15, 2020
On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>s&#2013266168;ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: >> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C >> <gnuarm.deletethisbit@gmail.com> wrote in >> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: >> >> > >> >He shows the only difference between patient triggered and machine triggered >> >waveforms is the negative pressure from the patient trying to draw air in >> >at the very start of the cycle. His diagrams are pretty poor with no registration >> >between the various points on different parameters, but he gets across >> >the main points. You can do a Google search to find other much better >> >diagrams. I don't think there are any new concepts to an engineer. >> >> No experience with these things >> but from _my_ life I know breathing is related to oxygen level in the blood. > >not really, your breathing is mostly related to the amount of CO2 in your lungs >that's why breathing something like pure nitrogen will kill you without you >even noticing
I wonder how many old ladies ricky's team plans to kill, trying to learn PIDs and stuff. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
On Sunday, August 16, 2020 at 11:14:22 AM UTC-4, jla...@highlandsniptechnology.com wrote:
> On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen > <langwadt@fonz.dk> wrote: > > >s&#371;ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: > >> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C > >> <gnuarm.deletethisbit@gmail.com> wrote in > >> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: > >> > >> > > >> >He shows the only difference between patient triggered and machine triggered > >> >waveforms is the negative pressure from the patient trying to draw air in > >> >at the very start of the cycle. His diagrams are pretty poor with no registration > >> >between the various points on different parameters, but he gets across > >> >the main points. You can do a Google search to find other much better > >> >diagrams. I don't think there are any new concepts to an engineer. > >> > >> No experience with these things > >> but from _my_ life I know breathing is related to oxygen level in the blood. > > > >not really, your breathing is mostly related to the amount of CO2 in your lungs > >that's why breathing something like pure nitrogen will kill you without you > >even noticing > > I wonder how many old ladies ricky's team plans to kill, trying to > learn PIDs and stuff.
Perhaps you will be the first little old lady? Care to volunteer? I love the fact that Larkin tells others to ignore me but can't resist reading and responding negatively himself! Yeah, that's a great community spirit. I'm glad Larkin is pulling for us all. At least he isn't making a personal attack like he criticizes others for... no, wait, he is! I would ask your opinion, but you have made it very, very clear that you don't actually understand the math of controllers, you just whip up a simulation and you are off to the races. I may well do that myself, but only after understanding the lung/air way model well enough to be sure the simulation is modeling something useful. -- Rick C. -+- Get 1,000 miles of free Supercharging -+- Tesla referral code - https://ts.la/richard11209
s&oslash;ndag den 16. august 2020 kl. 17.14.22 UTC+2 skrev jla...@highlandsniptechnology.com:
> On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen > <langwadt@fonz.dk> wrote: > > >s&#371;ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: > >> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C > >> <gnuarm.deletethisbit@gmail.com> wrote in > >> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: > >> > >> > > >> >He shows the only difference between patient triggered and machine triggered > >> >waveforms is the negative pressure from the patient trying to draw air in > >> >at the very start of the cycle. His diagrams are pretty poor with no registration > >> >between the various points on different parameters, but he gets across > >> >the main points. You can do a Google search to find other much better > >> >diagrams. I don't think there are any new concepts to an engineer. > >> > >> No experience with these things > >> but from _my_ life I know breathing is related to oxygen level in the blood. > > > >not really, your breathing is mostly related to the amount of CO2 in your lungs > >that's why breathing something like pure nitrogen will kill you without you > >even noticing > > I wonder how many old ladies ricky's team plans to kill, trying to > learn PIDs and stuff. >
I very much doubt they'll be allowed to hook anything living up to a ventilator hacked together by amateurs, no matter how well-meaning they are seems like an exercise in feeling like they are "doing something"
On Sunday, August 16, 2020 at 11:33:16 AM UTC-4, Lasse Langwadt Christensen wrote:
> s&oslash;ndag den 16. august 2020 kl. 17.14.22 UTC+2 skrev jla...@highlandsniptechnology.com: > > On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen > > <langwadt@fonz.dk> wrote: > > > > >s&#371;ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: > > >> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C > > >> <gnuarm.deletethisbit@gmail.com> wrote in > > >> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: > > >> > > >> > > > >> >He shows the only difference between patient triggered and machine triggered > > >> >waveforms is the negative pressure from the patient trying to draw air in > > >> >at the very start of the cycle. His diagrams are pretty poor with no registration > > >> >between the various points on different parameters, but he gets across > > >> >the main points. You can do a Google search to find other much better > > >> >diagrams. I don't think there are any new concepts to an engineer. > > >> > > >> No experience with these things > > >> but from _my_ life I know breathing is related to oxygen level in the blood. > > > > > >not really, your breathing is mostly related to the amount of CO2 in your lungs > > >that's why breathing something like pure nitrogen will kill you without you > > >even noticing > > > > I wonder how many old ladies ricky's team plans to kill, trying to > > learn PIDs and stuff. > > > > I very much doubt they'll be allowed to hook anything living up to a ventilator hacked together by amateurs, no matter how well-meaning they are > > seems like an exercise in feeling like they are "doing something"
There are a couple of companies we are talking to about running the design through a certification process and into manufacturing. So that will be covered. When we hit certain bumps in the road the solution is to not worry about it since the company taking it over will be redoing that anyway. This is not a rational to take technical shortcuts, more procedural things. So the documentation will be sparse I expect. That is my single biggest issue with the process. They are not doing a proper requirements analysis. This means many aspects of the design are not planned out properly and various sections have been redesigned several times and may be again in the future as we find bends in the road. Oh well, keeps me off the streets. I need to design a high side current monitor since the one in the motor controller has very poor accuracy. There is a nominal current ratio, but at lower currents the tolerance is worse than &plusmn;34%. -- Rick C. -++ Get 1,000 miles of free Supercharging -++ Tesla referral code - https://ts.la/richard11209
On Sun, 16 Aug 2020 08:33:12 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>s&#2013266168;ndag den 16. august 2020 kl. 17.14.22 UTC+2 skrev jla...@highlandsniptechnology.com: >> On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen >> <langwadt@fonz.dk> wrote: >> >> >s?ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: >> >> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C >> >> <gnuarm.deletethisbit@gmail.com> wrote in >> >> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: >> >> >> >> > >> >> >He shows the only difference between patient triggered and machine triggered >> >> >waveforms is the negative pressure from the patient trying to draw air in >> >> >at the very start of the cycle. His diagrams are pretty poor with no registration >> >> >between the various points on different parameters, but he gets across >> >> >the main points. You can do a Google search to find other much better >> >> >diagrams. I don't think there are any new concepts to an engineer. >> >> >> >> No experience with these things >> >> but from _my_ life I know breathing is related to oxygen level in the blood. >> > >> >not really, your breathing is mostly related to the amount of CO2 in your lungs >> >that's why breathing something like pure nitrogen will kill you without you >> >even noticing >> >> I wonder how many old ladies ricky's team plans to kill, trying to >> learn PIDs and stuff. >> > >I very much doubt they'll be allowed to hook anything living up to a ventilator hacked together by amateurs, no matter how well-meaning they are > >seems like an exercise in feeling like they are "doing something"
Exactly. I've seen this sort of thing before, a bunch of amateurs who plan to Save The World. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
On 8/16/2020 10:40 AM, Ricketty C wrote:
> On Sunday, August 16, 2020 at 3:02:23 AM UTC-4, bitrex wrote: >> On 8/16/2020 2:13 AM, Ricketty C wrote: >>> On Sunday, August 16, 2020 at 1:59:02 AM UTC-4, bitrex wrote: >>>> On 8/16/2020 1:47 AM, Ricketty C wrote: >>>>> On Sunday, August 16, 2020 at 12:32:46 AM UTC-4, bitrex wrote: >>>>>> On 8/16/2020 12:20 AM, bitrex wrote: >>>>>>> On 8/15/2020 9:44 PM, Ricketty C wrote: >>>>>>>> I understand the basics of PID design, but if you can't describe the >>>>>>>> thing being controlled, how can you design the controller other than >>>>>>>> trial and error? >>>>>>>> >>>>>>>> The "plant" is a motor on a tall reducing gear (~300:1) turning an arm >>>>>>>> that presses on a bag producing an air flow with the loop controlled >>>>>>>> by a pressure measurement. >>>>>>>> >>>>>>>> One issue I'm seeing discussed is a tradeoff on the PWM resolution vs. >>>>>>>> frequency.&nbsp; Presently they are using 3.6 kHz with 8 bit PWM control. >>>>>>>> I kinda wonder if a sigma-delta might be better, but that might >>>>>>>> require some external logic.&nbsp; They seem to be shy of pushing the CPU >>>>>>>> too much even after changing from an Arduino CPU at 20 MHz to an ARM >>>>>>>> CM4F at 80 MHz. >>>>>>>> >>>>>>>> The big concern is the overshoot when ramping up the pressure between >>>>>>>> exhale and inhale.&nbsp; In general, would it be better to simply jump the >>>>>>>> pressure set point at once and let the PID controller do its thing, >>>>>>>> optimizing the response time as best as possible controlling overshoot >>>>>>>> -or- would it be better to run up the pressure set point over a period >>>>>>>> of time which would seem to place less demand on the PID controller? >>>>>>> >>>>>>> as I understand it in supportive ventilation the pressure application is >>>>>>> triggered by patient breathing in, the pressure ramps up slowly to max >>>>>>> while sensing the back-pressure from the lung, then the flow rate ramps >>>>>>> down from peak in proportion to back-pressure as it starts rapidly >>>>>>> increasing near the end of the cycle. there's a trade off between slow >>>>>>> rise times and not hitting the required overall tidal volume, and fast >>>>>>> rise times which are uncomfortable for the patient! >>>>>>> >>>>>>> There are different control schemes; like time-cycled and volume cycled, >>>>>>> in time-cycled the total inspiration time is set and the mass flow rate >>>>>>> during the "flat" part of the curve is dynamically adjusted to deliver >>>>>>> the required volume, and volume cycled, where the peak mass flow rate is >>>>>>> fixed and the inspiration time varies. >>>>>>> >>>>>>> I don't think I would be "jumping" anything, the output pressure is not >>>>>>> a static value in either of the schemes AFAICT, always a dynamic >>>>>>> function of the back-pressure. the peak flow rate is related to peak >>>>>>> pressure but I don't think outlet pressure is the primary variable >>>>>> >>>>>> That is to say if the back-pressure starts increasing _for any reason_ >>>>>> you have to start dropping the outlet pressure proportionally you can't >>>>>> just set it and forget it! >>>>> >>>>> Not sure what you mean by outlet pressure and back-pressure. What is your model like? >>>>> >>>> >>>> There's some force per unit area of the air coming out of the tube into >>>> the lungs, and as air fills the lungs there's some back-pressure >>>> resisting that force from the weight of the atmosphere pushing down on >>>> the lungs. Like when you blow into a balloon. >>> >>> You reasoning still isn't clear to me. Everything has pressure from the atmosphere. That's why pressure in most cases is relative, not absolute. So that's simply not an issue. The balloon is elastic, that's why they require pressure to inflate. Inflating a paper bag is against air pressure only. >>> >>> What you are calling "back-pressure" is the combination of the dissipative effect (mostly moving air through the various forking passages I expect) and the compliance of the lungs (the elastic effect which actually does push back but without a lag). That is the pressure the vent has to assert to get air into the lungs, proportional to A*I + B*dI/dt which is what I've been describing all along. >>> >>> >>>> The early hydro-mechanical ventilators were back-pressure regulated; >>>> when back-pressure reaches a set point the exhale cycle is triggered. >>> >>> That might be a flow regulated unit. The flow is constant, so the pressure increases from the elastic effect until the volume is achieved and the exhale begins. >>> >> >> Yeah, don't see what else it could be I guess when it's entirely powered >> by the air supply. > > The difference is what is controlled. There's no reason why the pressure could not be controlled and then timed or still work off the volume. In fact, it seems to me the flow rate controlled system *could* be timed to get an accurate volume while the pressure controlled system will produce a variable volume depending on the patient parameters. There's still a lot missing. > > >> If the PID is controlling pressure tho and what you're actually >> measuring is pressure differential the thought occurred to me, if you >> just set it to what the pressure is supposed to be during the main >> portion of the inhale to get the volume and let the PID "do its thing" >> what happens if for some reason the patient starts actively pushing back >> while it's ramping up does the PID read this as "pressure too low" and >> start trying to force it in harder? and then they stop and it can >> overshoot? I mean I guess they'd be sedated so that might be unlikely > > You just said the pressure is controlled. So it won't "push back harder". That would be the flow controlled system in which the pressure will vary according to the patient parameters - spring and dashpot and of course if he is awake, breathing back against the machine. "Assist" means the patient is awake. This is the mode the "amateur" systems seldom tackle, so we are adding that.
Ok I see what you mean, imagining like a tire-pressure gauge tapped off the tube somewhere, as a crude analogy. Whether it's the bag pushing air in, or the patient blows back, or both, the pressure in the tube will rise. So worst-case it would undershoot, not overshoot. I think. I was just wondering because while a sedated patient's lungs may be like an...RC circuit you say? an awake patient has a diaphragm and they can use it to fight the vent, in some situation perhaps. The physiology of conscious patients on ventilators is unclear to me I'd assume they can and will do whatever at some point. I'd think you'd want a controlled pressure ramp-up to ensure they're not doing that until it levels off. Then the PID kicks in for the constant rate phase and if they fight it at that point the control loop naturally ends the cycle early. and I'd guess in the pro stuff too many short cycles where the desired tidal volume hasn't been delivered triggers an alarm.
> Sometimes I just want to hit my head on the floor. The guy adds a very demanding mode after much of the design is supposedly done and still wants to push for getting it done quickly because people are getting tired of working on this.
Welcome to having clients, even hardware ppl are expected to be "agile" nowatimes
> This sort of inconsistency is rife in this project. I wanted to get rid of the ten cent thermistor (that's about 1 and 6 old currency) for a linear device that cost a dime. People were complaining about the cost. Mean while we have $100 in sheet metal, a $30 motor and gear train, three $20 pressure sensors and a $30 O2 sensor! They don't want me to use parts that do a better job if they aren't in inventory in the ten thousands, but the pressure sensors are hardly stocked anywhere. > > Now we are trying to pick a new motor and the one they picked can trash the gears if run against a stop. The currents at the max peak rating and the max continuous rating are so close that the inaccuracies in the current sensor in the motor controller are larger. > > So many things would have been worked out had we done a proper requirements analysis. The first two sets of boards are not functional enough to verify circuits work like the battery charger (I think the input voltage is too low to fully charge the battery as the charging chip is designed - Vboost is 14.6, Vin is nominally 15V but there's tolerance - not to mention drop out voltage!). Still, they are rushing to get the next rev of the board done. > > The last couple weeks I've been wanting to walk away, but I'd like to get through a design review on the board. I asked to add hysteresis to the alarm comparators (fully hardware, no software) and provided an LTspice schematic which had been verified in simulation. The schematic has negative feedback instead of positive. > > I know, I know, I'm whining at this point. Thanks for listening. >
On 8/16/2020 11:48 AM, jlarkin@highlandsniptechnology.com wrote:
> On Sun, 16 Aug 2020 08:33:12 -0700 (PDT), Lasse Langwadt Christensen > <langwadt@fonz.dk> wrote: > >> s&oslash;ndag den 16. august 2020 kl. 17.14.22 UTC+2 skrev jla...@highlandsniptechnology.com: >>> On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen >>> <langwadt@fonz.dk> wrote: >>> >>>> s?ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: >>>>> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C >>>>> <gnuarm.deletethisbit@gmail.com> wrote in >>>>> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: >>>>> >>>>>> >>>>>> He shows the only difference between patient triggered and machine triggered >>>>>> waveforms is the negative pressure from the patient trying to draw air in >>>>>> at the very start of the cycle. His diagrams are pretty poor with no registration >>>>>> between the various points on different parameters, but he gets across >>>>>> the main points. You can do a Google search to find other much better >>>>>> diagrams. I don't think there are any new concepts to an engineer. >>>>> >>>>> No experience with these things >>>>> but from _my_ life I know breathing is related to oxygen level in the blood. >>>> >>>> not really, your breathing is mostly related to the amount of CO2 in your lungs >>>> that's why breathing something like pure nitrogen will kill you without you >>>> even noticing >>> >>> I wonder how many old ladies ricky's team plans to kill, trying to >>> learn PIDs and stuff. >>> >> >> I very much doubt they'll be allowed to hook anything living up to a ventilator hacked together by amateurs, no matter how well-meaning they are >> >> seems like an exercise in feeling like they are "doing something" > > Exactly. I've seen this sort of thing before, a bunch of amateurs who > plan to Save The World. >
Me too. and they always seem to make Jared Kushner the team lead.
On 8/16/2020 11:14 AM, jlarkin@highlandsniptechnology.com wrote:
> On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen > <langwadt@fonz.dk> wrote: > >> s&oslash;ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: >>> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C >>> <gnuarm.deletethisbit@gmail.com> wrote in >>> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: >>> >>>> >>>> He shows the only difference between patient triggered and machine triggered >>>> waveforms is the negative pressure from the patient trying to draw air in >>>> at the very start of the cycle. His diagrams are pretty poor with no registration >>>> between the various points on different parameters, but he gets across >>>> the main points. You can do a Google search to find other much better >>>> diagrams. I don't think there are any new concepts to an engineer. >>> >>> No experience with these things >>> but from _my_ life I know breathing is related to oxygen level in the blood. >> >> not really, your breathing is mostly related to the amount of CO2 in your lungs >> that's why breathing something like pure nitrogen will kill you without you >> even noticing > > I wonder how many old ladies ricky's team plans to kill, trying to > learn PIDs and stuff. > > >
The Bird Mark 8 was a pretty simple, totally hydro-mechanical gizmo. 1940s tech, used in hospitals in the US well into the 1970s and probably longer elsewhere. "This is not an exact science, probably at best a guess": <https://youtu.be/SG3zlpRSfWE?t=102> Still, probably saved way more old ladies than it killed. Some device like OP is talking about with an electronically-controlled squeeze-bag seems to intrinsically limit the potential hazardous failure modes. You only have so much air to work with and the mechanical "squeezer" can only physically move so fast. High-performance ventilators use electric blowers and there's a lot more to go wrong, there. Good news! The schematic of the blower board I looked at had a 555. The lil 555, out there saving lives every day.
On 8/16/2020 12:46 PM, bitrex wrote:
> On 8/16/2020 11:14 AM, jlarkin@highlandsniptechnology.com wrote: >> On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen >> <langwadt@fonz.dk> wrote: >> >>> s&oslash;ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: >>>> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened >>>> Ricketty C >>>> <gnuarm.deletethisbit@gmail.com> wrote in >>>> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: >>>> >>>>> >>>>> He shows the only difference between patient triggered and machine >>>>> triggered >>>>> waveforms is the negative pressure from the patient trying to draw >>>>> air in >>>>> at the very start of the cycle.&nbsp; His diagrams are pretty poor with >>>>> no registration >>>>> between the various points on different parameters, but he gets across >>>>> the main points.&nbsp; You can do a Google search to find other much better >>>>> diagrams.&nbsp; I don't think there are any new concepts to an engineer. >>>> >>>> No experience with these things >>>> but from _my_ life I&nbsp; know breathing is related to oxygen level in >>>> the blood. >>> >>> not really, your breathing is mostly related to the amount of CO2 in >>> your lungs >>> that's why breathing something like pure nitrogen will kill you >>> without you >>> even noticing >> >> I wonder how many old ladies ricky's team plans to kill, trying to >> learn PIDs and stuff. >> >> >> > > The Bird Mark 8 was a pretty simple, totally hydro-mechanical gizmo. > 1940s tech, used in hospitals in the US well into the 1970s and probably > longer elsewhere. > > "This is not an exact science, probably at best a guess": > > <https://youtu.be/SG3zlpRSfWE?t=102> > > Still, probably saved way more old ladies than it killed.
Essentially on that one they put the "control loop" controls on the front panel and expect the medic to use their brain
On 8/16/2020 11:33 AM, Lasse Langwadt Christensen wrote:
> s&oslash;ndag den 16. august 2020 kl. 17.14.22 UTC+2 skrev jla...@highlandsniptechnology.com: >> On Sun, 16 Aug 2020 07:53:41 -0700 (PDT), Lasse Langwadt Christensen >> <langwadt@fonz.dk> wrote: >> >>> s&#371;ndag den 16. august 2020 kl. 16.31.14 UTC+2 skrev Jan Panteltje: >>>> On a sunny day (Sat, 15 Aug 2020 22:46:45 -0700 (PDT)) it happened Ricketty C >>>> <gnuarm.deletethisbit@gmail.com> wrote in >>>> <d2d879c1-cf13-42f8-9727-8ef27dc2dc65o@googlegroups.com>: >>>> >>>>> >>>>> He shows the only difference between patient triggered and machine triggered >>>>> waveforms is the negative pressure from the patient trying to draw air in >>>>> at the very start of the cycle. His diagrams are pretty poor with no registration >>>>> between the various points on different parameters, but he gets across >>>>> the main points. You can do a Google search to find other much better >>>>> diagrams. I don't think there are any new concepts to an engineer. >>>> >>>> No experience with these things >>>> but from _my_ life I know breathing is related to oxygen level in the blood. >>> >>> not really, your breathing is mostly related to the amount of CO2 in your lungs >>> that's why breathing something like pure nitrogen will kill you without you >>> even noticing >> >> I wonder how many old ladies ricky's team plans to kill, trying to >> learn PIDs and stuff. >> > > I very much doubt they'll be allowed to hook anything living up to a ventilator hacked together by amateurs, no matter how well-meaning they are > > seems like an exercise in feeling like they are "doing something" >
In a modern Western hospital run by insurance companies with other better options available? No, probably not. In a field hospital in a crisis, or in the third world, where there's nothing else available and there aren't bureaucrats up your ass? They'll throw tin cans and twine at a situation if it's thought it would be of help. The Hippocratic Oath says "First do no harm.." but if the patient is clearly dyin' anyway, y'know.