Baseline and Acceleration Episodes - Clinically Significant Nonstationarities in FHR Signal: Part I. Coefficients of Inconsistency

Abstract

Fetal heart rate (FHR) is the main source of information on the fetal state. FHR is characterized by two components: the basal fetal heart rate (baseline) and the variability of FHR — mainly accelerations (A) and decelerations (D). A correctly determined FHR baseline is a precondition for correct identification of the acceleration and deceleration patterns. Even a small inaccuracy in the FHR baseline curve may significantly distort the detection of A/D, which may subsequently lead to false interpretation of clinical symptoms. It is necessary to develop a method and criteria, which would allow evaluation of the baseline algorithms. The algorithms could be evaluated either by means of direct comparison of baselines or by a comparison of A/D patterns. The paper presents a method which can be used to determine matched A/D patterns recognized using two various baselines in the meaning of their time location. The method uses the coefficients of inconsistency between these patterns.