Technical problems in STV indexes application

Abstract

Cardiotocography (CTG) is the most widely used diagnostic technique to monitor fetal health. Its usefulness is undoubted; however, several analysis methodologies were proposed in recent years to improve its reliability and objectivity. To this end, great interest was dedicated to the Variability of the Fetal Heart Rate (FHRV). In particular, Short Term Variability (STV), which reflects changes in consecutive beatto- beat intervals, in general reveals autonomic nervous system functioning. Many groups of researchers described time domain parameters for quantifying FHRV. However, there are marked differences in the methodologies used, making comparison difficult, while there is no many comprehensive studies of all the indices. This work aims to analyze technical characteristics and problems related to the CTG application and comparison of some STV indexes proposed in literature and/or used in clinical environment. 9 different STV indexes were programmed and then compared by means of simulated FHR signals. In particular, we analyzed their dependence on CTG sampling frequency and FHR mean. Moreover, the indexes were evaluated for their capability to return the imposed value of FHRV. Obtained results show that can be preferable to use the standard deviation to evaluate STV.