Analyzing fetal breathing rates using matching pursuits

Spontaneous breathing movements in the fetus tend to occur intermittently, and do not become continuous until after birth. In both the primate and the ovine species, breathing movements have been observed to have a high degree of variability in instantaneous breathing rates. In this study, ewes were surgically instrumented for chronic intrauterine recording of fetal diaphragmatic EMG. The matching pursuit (MP) method was used to examine the effects of morphine on fetal breathing rates in both time and frequency domains. The matching pursuit method was chosen since the classical Fourier transform may not represent signals which have stationary characteristics and wavelet transform may not represent signals whose Fourier transforms have a narrow frequency support. The authors´ results show that the MP method was superior to both short time Fourier and wavelet transforms in identifying multiple periodicities in a highly nonstationary signal such as fetal breathing