A DPCM based Electrocardiogram coder with thresholding for real time telemonitoring applications

This paper illustrates a DPCM based approach for real-time compression of ECG data for real time telemonitoring application. For real time implementation a `frame' is considered with one original sample followed by 64 first difference elements. The coder compresses the non-QRS regions of an ECG data stream through stages of first difference, joint sign and magnitude coding, and run length encoding. A hard thresholding at the equipotential regions have been applied to enhance the RLE efficiency. For testing 10 second ECG data from Physionet has been used with 10-bit quantization level. The CR, PRD and PRDN achieved with PTB Database (ptbdb) are 6.42, 9.77 and 9.77 respectively. With MIT-BIH arrhythmia data (mitdb), these values are 5.92, 8.19 and 8.19 respectively. With MIT-BIH ECG Compression test data (cdb), these values are 4.25, 5.37 and 6.65 respectively. The frame wise compression rises to a value of 12-14 in flat (TP) segments and low 1-2 in QRS regions. The computational simplicity of the algorithm provides an opportunity to implement the coder using a low cost microcontroller.