Coping with limitation of bedside measurement instrumentation for reliable assessment of fetal heart rate variability

Abstract

Estimation of the instantaneous variability of the fetal heart rate (FHR) is affected by the autocorrelation techniques commonly used in Doppler ultrasound channel of today's fetal monitors. Considerably decrease of short-term variability have been noted, which is quite surprising because the fetal monitors determine the fetal heart rate with quite satisfying accuracy in relation to the reference direct fetal electrocardiography. The aim of this work was to recognize a source of errors and to develop the method for correction of the indices describing the FHR variability for a given type of fetal monitor. The proposed correction relies upon removing of the constant error component, which has been assigned to an averaging nature of the autocorrelation function. Although the remaining random error component is still not too satisfactory considering the instantaneous values, a significant improvement of reliability of the fetal heart rate variability measurement was confirmed in case of a global one-hour trace assessment. © 2008 Springer-Verlag Berlin Heidelberg.