Partial Directed Coherence (PDC) method and its extensions proved to be useful tools in analysing couplings in multivariate dynamic systems. We introduced the normalised short time PDC method (NST-PDC), to investigate the dynamic behaviour of couplings. First simulated signals obtained from coupled oscillators were analysed and information about the dynamical behaviour of the virtual system achieved. Then, as a first preliminary test applying the NST-PDC method, we observed significant (p< 0.05) coupling dynamics differences in pregnant woman with hypertensive disorders, by comparing patients with preeclampsia and chronic hypertension. The NST-PDC is applicable for nonstationary time series, detects dynamical changes of coupling and might be usable for the analysis of time dependent cardiovascular couplings.