I am measuring ECG signals on subjects and I am having issues filtering a very small signal from the inherent noise of the collecting device. I am using an 18 bit ADC to digitize the signal
Here is an example of the noisy signal I get:
I would like it to look like this:
I have tried different filters and the best signal yet has been from the 8-point mean averaging of the signal:
However, I am trying to find the p-wave, which is a small upward deflection just before the large QRS complex of the pulse. This p-wave is buried in the noise and I can't seem to get it out. I have tried creating a median beat of 300 heartbeats, and by doing this I can show that the p-wave does exist, but I need to show that it exists for every heartbeat.
Is there a more elaborate way to tease out the p-wave using the median beat, or could you point me to other strategies for improving the signal to noise ratio?