Statistical fluctuations in heart rate variability indices

Heart rate variability and electrocardiogram changes in the fetal lamb during hypoxia and beta-adrenoceptor stimulation

“…After studies on a simulated signal DETWILER etal. [6] suggested that an epoch length of at least five minutes was necessary to obtain good estimates of short-term variability indices. However, KARINIEMI et al found a good correlation between one-minute and five-minute epochs for estimation of DI [18].…”

“…The length of the time period during which FHRV is analysed influences the result [4]. An epoch length of at least five minutes has been suggested to obtain good estimates of short-term variability indices [6]. However, long epochs are advantageous only of the indices can be assumed to be stationary throughout the epoch.…”

“…Bei der Analyse der FHRV beeinflußt die Auswertungsdauer das Ergebnis [4]. Um die Kurzzeitvariabilität richtig einschätzen zu können, wird eine Beobachtungsperiode von mindestens 5 Minuten gefordert [6]. Darüber hinaus muß man von der Annahme ausgehen, daß sich die Indizes auch außerhalb der Beobachtungsphasen stationär verhalten.…”

Evaluation of Fetal Heart Rate Baseline Estimation Method Using Testing Signals Based on a Statistical Model

“…These oscillations are called longterm variability [4]. Essential element used to generate short-and longterm variability is the autoregressive filter [7], [8]. The idea of the autoregressive method is based on assumption that signal can be represented as a white noise signal passed through the filter of the following transfer function:…”

Technical Aspects of Fetal and Intrauterine Pressure Monitoring

“…Since the majority of normal beat-tobeat ("short-term") fetal heart rate variation is less than 4 msec (equivalent to 1.3 bpm at 140 bpm) (Wheeler et al, 1979), it can only be measured accurately using special electronic and statistical techniques. [For further references on the measurement of beat-to-beat fetal heart rate change, see the following: Dalton and Holt (1976), Dalton et al (1977), De Haan et al (1971, Detwiler et al (1980), Henry et al (1979b), Laros et al (1977), Lauersen et al (1976), Modanlou et al (1977), Yeh et al (1973), and Steer Young et al (1976)]. It cannot be seen on the cardiotocogram with a paper speed of 1 or 3 cm/min unless the change of rate is very rapid, or the chart speed is increased considerably ( Figure 5) (Steer, 1977b).…”