A comparison and quantification of fetal heart rate variability using Doppler ultrasound and direct electrocardiography acquisition techniques

This paper presents a novel efficient technique for processing of the Doppler ultrasound signal which could estimate the cardiac cycle duration with accuracy comparable to direct electrocardiography. Direct electrocardiography as a reference technique up till now ensures the highest possible accuracy of heart interval measurement. The proposed method has been developed to calculate beat-to-beat basis power spectral information on the fetal heart rate (FHR) in stages of pregnancy earlier than labor from Doppler ultrasound signal. The developed real time Doppler ultrasound fetal data acquisition technique & real time direct fetal electrocardiogram (FECG) has been tested in a local hospital on a sample group of 35 pregnant women at different interval during gestation period. The results revealed that Doppler ultrasound method enables to calculate reliable parameters describing the variability of FHR compared to the direct fetal electrocardiogram. This reliable Doppler ultrasound system detects all fetal heart beats reducing the number of invalid cardiac cycle measurements considering limitation of measuring system parameters in five minutes recording of each subject. The processing of acquired signals was implemented using LABVIEW environment virtual instrumentation software system. National Instruments ELVIS II+ with USB plug-and-play capabilities was utilized for data acquisition and display of FHR signal from Doppler ultrasound system for quantification of heart rate variability.