1/f Fluctuations of breathing rate in fetal sheep and IPFM model

Fetal breathing rates (FBR) in sheep have been investigated using spectral analysis techniques. The power spectral densities of the FBR were found to be inversely proportional to Fourier frequency (1/f spectrum) below 0.06 Hz. The levels of the 1/f spectrum are same with changing the morphine dose, when normalized by the mean square of the data. In order to simulate 1/f fluctuation of the FBR, the integral pulse frequency modulation (IPFM) model is used, and parameters were fluctuated various random noise. As a result, 1/f fluctuation similar to the experimental data is obtained with the 1/f fluctuation of the parameters.