Reduction of CPR artifacts in the ventricular fibrillation ECG by coherent line removal

Table 1 SNR-gain by coherent line removal

VR-to-CPR ratio [dB]	snr-gain (optimized parameters) n = 168	snr-gain (fixed parameters) n = 168
-20	10.3 ± 2.0	9.3 ± 2.4
-15	10.5 ± 2.2	9.4 ± 2.4
-10	10.5 ± 2.6	9.5 ± 2.5
-5	10.2 ± 2.8	9.3 ± 2.5
0	8.9 ± 2.9	8.0 ± 2.7
5	6.3 ± 3.7	4.9 ± 3.7
10	1.7 ± 4.0	-1.0 ± 4.0

For the results of this table, 14 different human VF-ECGs (without CPR-related artifacts) have been mixed with 12 different ECG containing CPR-artifacts only at a VF-to-CPR ratio of -20 dB, -15 dB, -10 dB, -5 dB, 0 dB, 5 dB and 10 dB. Typical VF-to-CPR ratios in Fig 4 were in a range of [-20 dB, -5 dB]. In these particular simulations, the human ECG mixed with CPR-ECG had a "fibrillation band" in the frequency range [1 Hz, 5 Hz], which is expected to be difficult to separate from CPR-related artifacts with ~1.8 Hz and harmonics at ~3.7 Hz, ~5.5 Hz etc. After estimation of CPR-artifacts by coherent line removal, the SNR-gain can be determined. Since coherent line removal can be performed using different parameters (such as the number of harmonics used for the estimation of the CPR-related artifacts in the ECG), one gets snr-gains for every set of parameters. Optimizing the parameters of the algorithm results the SNR-gains shown in column 2 of the Table. Using a the fixed set of default parameters (10 harmonics for analysis and reconstruction and delta = 4) for all different VF-to-CPR ratios still give considerable snr-gain for VF-to-CPR. Results deteriorate if CPR-content in the signal is low (as is the case for a VF-to-CPR ratio of 5 dB). This is what we expected: if almost no CPR-artifacts are present in the signal, the estimation of these very low CPR-artifacts becomes impossible even with most sophisticated techniques.

ISSN: 1475-925X