Simulation of cardiac RR interval time series

An RR interval simulator was developed as part of the Computers in Cardiology Challenge (entry no. 184). The simulator was based on observed physiological changes in normal subjects. A template, which represented slow trends in RR interval during 24 hours, was derived from a number of parameters that represent sleep and wake states. The variations about the template were generated so that the frequency spectrum of the final signal was similar to data from normal subjects. The frequency spectrum of normal RR intervals shows a strong 1/f component, a peak at around 0.1 Hz and a peak corresponding to respiratory rate between 0.15 Hz and 0.4 Hz. These were simulated by adding to the template pink noise, a number of random phased sinusoids at around 0.1 Hz and a signal that represented respiration. Variations due to respiration were dependent on sleep and wake states.