On the accuracy of fetal heart rate variability (STV and LTV) measurement.

概要

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A basic study on the accuracy of fetal heart rate measurement has been performed experimentally using a signal generator as the FHR generator. It was found that a measurement error of 3.5ms or less was necessary to conclude that the existence of variability at the fetal heart beat rates of around 140bpm was a reality and that it was not false variation caused by noise. The measurement accuracy of the cardiotocomonitor used in these experiments was 0.78ms when measuring fetal heart beat rates of 140bpm.Meanwhile, the following equation holds between the lowest value for STV (short-term variability) which can be measured accurately and the measurement error (in this case, the STV index is the one proposed by Heilbron).STV=0.159σε, STV=√1-ρ/2σ; that is, ρ, represents the correlation coefficient between Ti and Ti+1, while σ represents the standard deviation of Ti.It can be concluded that a measurement accuracy of 0.156ms is required to measure STY of 1ms accurately. Inversely, STV of 5 ms is the lowest value which can be measured with an accuracy of 0.78ms. A higher measurement accuracy will be needed to clarify the ambiguous clinical significance of STV.
一般社団法人日本生体医工学会の論文