Performance of a method to generate fetal cardiotachograms using fetal phonocardiography

The capability of a fetal phonocardiogram (PCGf) processing method to generate reliable time series has been evaluated. 29 simultaneous PCG and ECG signals were recorded from 18 adults and 11 fetuses. Each PCG signal was processed to extract the starting (S), maximum (M) and ending (E) points from the envelope of the cardiac sounds S1 and S2. The PCG time series (S-S, M-M and E-E) were compared with the ECG pattern signal by using time and heart-rate frequency variability indexes derived from each time series. Data were analysed using ANOVA and post-hoc tests for repeated measures. Results on adults have shown that, with the proposed method, S_S1, M_S1, S_S2 and M_S2 are reliable time references to generate time series (p>0.05). On fetal signals, because of the recording setup, the method´s performance has been limited to detecting M_S2 as the only reliable time reference. Thus, PCGf is a reliable source to produce at least one time series that is equivalent to the pattern signal