An ECG signal compression technique using ASCII character encoding

Efficient software based new ECG data compression algorithm is developed here. The whole algorithm is written in the C-platform. The algorithm has been applied to various ECG data of all the 12 leads (i, ii, iii, avr, avl, avf, v1, v2, v3, v4, v5, v6), taken from PTB Diagnostic ECG Database (ptbdb). In this method, only the “Voltage” values are gathered from the corresponding input ECG data and then those are multiplied by a considerably large integer number to convert them into integer. In the next step, these integer numbers are grouped maintaining some logical criteria. This grouping is functioning as the main compression technique. In this technique the grouping has been done in such a way that every grouped number resides under valid ASCII value. Then all the grouped numbers along with sign bit and other necessary information are converted into their corresponding ASCII characters. It is observed that this proposed algorithm can reduce the file size significantly. The data reconstruction algorithm has also been developed using the reversed logic and it is seen that data is reconstructed preserving the significant ECG signal morphology. Basically, ECG is a voltage–time characteristic and since the sampling time is constant, the “time” data can be automatically reconstructed at the receiving end. Therefore concentration has been given only to compress the ‘Voltage’ values.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Only ECG ‘Voltage’ values are taken. ► Associated information like sign-bit, ‘rs’ and amplification factor are generated. ► ‘Voltage’ values are amplified, grouped and printed in ASCII character. ► ECG signal is reconstructed using the reverse logic of compression with PRD 7.89%. ► Compressed file can be transmitted over GSM network as SMS based text message.