Mechanical ventilator simulation

[MMozart]

Hello! Im doing my master  thesis ( "Simulation of mechanical respirator and telemonitoring of the device and the patient" ) in Labview. I faced with the problem of simulating volumen of lung during respiration. Volumen as a function of time is modeled with equations ( inspiration and expiration 😞

V(t)=C1+C2(exp(-t/0,5)

V(t)=C1+C2(1-exp(-t/0,5))

How to make from this signals one periodic signal  where I can modify amplitude and frequency? I suppose that the problem is quite simple but i can't see the solution at this moment. Thank you all for your time. 

[Kristen_K.]

Hi MMozart,

There are a couple of options- although some more details would be helpful.   Are you wanting to combine these two equations into one?  What have you tried so far?

As far as some options, take a look at the Mathscript node, the formula node, or the expression node. 

Kristen H.

[MMozart]

Hello Kristen,

Firstly, thank you for you time.

Respiration model can be devided in two parts : inspiration and expiration. Inspiration is modeled using function Vinsp(t)=C1+C2(1-exp(-t/0,5) and expiration si modele using function  Vexp(t)=C1+C2(exp(-t/0,5)).I would like to generet signal as shown on Figure ( blue line ) and show generated signal on scope or graph.  After that signal values will be extracted  every 2 minutes and that would make a log of patient respiration during tretmant with mechanical ventilator. Also, i need to change amplitude ( tidal volume of lung ) and frequency ( breath per minute ) without distorting signal ( incomplete rising or falling edges ).

 

[Kristen_K.]

Hi MMozart,

Here is a VI that I think should get you started.  It uses a state machine to go back and forth between inhale and exhale but allows for the user to stop anytime between an inhale or exhale.  You will need to play with the values to get better looking data and may need to make some changes, but i think this might be a good start.  The VI is in LV 2009, btw, let me know if you need a previous version.

Kristen H.

[MMozart]

I have LabView 8.5 so I will need previous version. Thank you very much for your effort and time.

[Kristen_K.]

Here's the LV 8.5 version....

Kristen H.

Message Edited by Kristen H. on 02-04-2010 10:55 AM

[MMozart]

This would be very useful, thank you very much. I think that I found more easier way to implement this but I have some problems, again. This signal is simple pulse response of RC circuit. According to differential equation that describe this system, model that will give wanted output is shown on figure.

How to implement this in LV 8.5? I tryed  but for every solution and alternative I get value 0 after the subtract block in LV. I assume that the problem is something about feedback node?

 

[Andy_C.]

Hello MMozart,

You can use LabVIEW Control Design and Simulation Module for that.

[Kristen_K.]

Hi MMozart,

Andy is exactly right.  Do you have Control Design and Simulation Module?   

Kristen H.

[MMozart]

No, I dont have Control Design and Simulation Module. I know that this is the best tool to solve this problem but Im wondering what is problem with VI that I modeled in LV 8.5.In fact, here are the signals Im trying to generate.

Thank you all 🙂