Hi,

I've got another project for my medical research I need help with. I have an MRL PIC-50 monitor that reads exhaled CO2. I'd like to be able to monitor this in realtime using my national instruments box and labview. The problem is the monitor was built for use on an ambulance and doesn't have any analog outputs. It has an RS232 port for fax communication but I don't think it will send any real-time data through it. I have the service manual with schematics. I'm wondering, is it even possible to get this data? If so, what is the best way? Pulling an analog signal off of a point I've soldered onto the board somewhere, or trying to reprogram the machine to send the CO2 data through the RS232 port? Anybody ever done something like this?

Thanks

The link to the service manual is here: http://www.frankshospitalworkshop.c...IC30,40,50_Defibrillator_-_Service_manual.pdf

 

You might consider skipping the monitor and going straight to the probe. With Labview you should have no problem doing whatever time sampling and profiles you need. You may need an op-amp to condition the signal - that depends on what the probe does.

Are you familiar with capnometers (CO2 meters)? Depending on the data you need, you should be aware that CO2 changes throughout a breathing cycle, and the shape of that profiles contains diagnostic information. A single value can be chosen, but it glosses over a lot of info.

Any idea what that "1V output" thing is about?

 

I'm pretty familiar with the reading of the capnograph, just not the exact operation of the probe. Like you suggested, I would like to get a realtime waveform off of it. I hadn't thought of going straight to the probe, but that is certainly an idea. The only thing I wonder though, is how to keep it calibrated. The monitor pauses readings every 30 seconds or so to recalibrate the probe (how it does this I'm not sure as nothing mechanical happens, it's all automatic). If I just pulled a reading off with labview it wouldn't calibrate.

My particular monitor has an RJ-45 connector for fax output rather than the 1v output. But I think all of this is only for transmitting 12 lead ecg's not CO2.

 

Any idea on the RS-232 port? Could I just plug it into my computer and use it without special software?

 

No, you would definitely need software. You need to send commands to the device and receive back a result. I once used a digital scale this way, to automate collection of thousands of weighings. The manual seems almost silent on using that port - or at least I didn't see anything - so I wonder if there is another manual describing that interface.

 

If you have a monitor working and transmitting, you could snoop the data stream with a comm analyzer and figure out the command structure.

 

I agree, I was thinking about trying to find an open source serial comm analyzer and seeing what I could figure out. Probably not much as my programming skills are VERY basic and I know nothing about serial comms.

I couldn't find much of anything about what is output through the rs-232 anywhere in the manual either. And unfortunately MRL was bought by Welch-Allyn who discontinued them nearly immediately and then sold the warranty service to Zoll who doesn't know or care about this product, so I can't find anyone who knows anything about it cause the people that did know have all found other jobs by now.

This problem has been slowly frustrating me for about 2 years now...

 

It looks like a pretty old defibrillator if it has a modem board? It's many moons ago but have a look at HyperTerminal software in Windows it may be able to pull the information out you need? Can't offer much more I'm afraid.