I have the ReadMyHeart (RMH) V2.0 and take EKGs nearly every day. In December, it probably saved my life, as my deteriorating EKGs were the ONLY symptom I had of a seriously clogged heart. Fortunately my Doctor was a believer in the printouts I had made. After a quad bypass, I continue to use it.
One advantage of using a personal handheld EKG over the conventional physician's EKG, is that I can take an EKG after a preset amount of exercise. Generally, the doctor only does a resting EKG unless it is a Stress Test or he has you wear a Holder for 24 hours - both of which are very good, but a lot more expensive than the one done in the office.
I can make an educated guess about the operation from observation and the manual, which is publically available.
RMH uses thumb contacts to get the EKG across the arms. The contacts are probably a special material - but that is not of much concern to you. The EKG made is only a single view of the voltages taken "across the heart". It is probably the most meaningful single view, but no substitute for the 12 views a physician has from a professional machine.
The first 10 seconds of the operation are used to find the signal and obtain the DC baseline of the EKG voltage. These data are not recorded to memory.
In RMH, there is no realtime display of the EKG waveform. Frankly, you could only see a transient few seconds at any decent resolution on a few inch display, so my opinion is a realtime display is not too useful in real life (some exceptions I suppose if you can interpret transients). It may be a nice idea for your project though. Perhaps you could scroll back through it after the EKG data was recorded to make a live display useful.
Seconds 10 to 25 apparently use the measured baseline and also some filtering. Maybe digital, maybe analog. These data are recorded to a 30 record memory.
Hardware Specs:
Input impedance: 10 Mohm
Input dynamic range +- 2mV
CMRR >60 dB
AD Conversion 12 bit
Sample frequency 120 S/sec
The BPM heartrate is displayed in realtime for the last 15 seconds and sometimes for part of the first 10 seconds. After using the machine for maybe a hundred recordings on the same person and seeing the EKGS later, one may be able to make an educated guess from just seeing the changes in HR each second, that problems are occurring or not. This is no substitute for seeing the detailed EKG however.
At the end of 25 seconds, an in-machine analysis of the data is done and the following EKG parameters are displayed:
Heart Rate XXX BPM
ST depression x.xx sec
QRS x.xx sec
If they are out of conventional specs, they blink.
The data are downloaded to a windows computer through a special USB-like connection. In the unit I have, the EKG plots and some rudimentary analysis can be seen on the computer screen and printed. (Sample attached)There is also a database of EKG records that has simple management by patient.
In case someone happens on this description through a search, there is apparently also another, relatively new version (2012?) of this machine that is the "OTC" (Over The Counter) version, Model 100. It is not compatible to the Model V2 in USB connection or software. I am told in that version, which is sold for about half the price of the V2.0 machine, that the EKG graphing software is not furnished with the machine. The data is apparently uploaded, but only plots of the HR, ST and QRS are made. In my opinion, that makes it much less useful to the user or to a doctor. Depending on who sells it, you may be able to get the EKG display software as a quite expensive option - and perhaps only with a physician's prescription. Ah, such protection we enjoy.
I don't think you will get into any problems with the US government for doing this as a student project. They seem to be very cautious of letting these machines be sold if they include enough information for the user try to interpret the data themselves. And there is merit to that point of course. Unfortunately, if you dumb down the output, then it is also useless to a doctor.
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