ST waveform analysis for monitoring hypoxic distress in fetal sheep after prolonged umbilical cord occlusion

Figures

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  Fig 1. Blood gas analysis during normoxemia and hypoxemia. Whisker plots for arterial blood pH (panel A), base excess (panel B), partial arterial oxygen pressure (panel C) and partial arterial carbon dioxide pressure (panel D), with whiskers extending up to 1.5 times IQR. Blood gasses were assessed during baseline, during (5-10-15-20 minute) umbilical cord occlusion and during reperfusion. Outliers are displayed as circles.

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  Fig 2. Blood pressure and heart rate response during normoxemia and hypoxemia. Mean arterial blood pressure (BP), heart rate (HR, beats per minute, bpm), heart rate variability (expressed as SDNN, ms) and T/QRS ratio during baseline, UCO (T = 0–25 minute) and reperfusion of all subjects. The mean values are shown with 95% confidence intervals. Note the marked bradycardia and initial hypertension directly after cord occlusion; during occlusion a sustained bradycardia and progressive hypotension was observed. After umbilical cord occlusion, the reperfusion period showed a marked decrease in SDNN compared to the baseline period.

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  Fig 3. STAN-events during normoxemia and hypoxemia. Subjects with STAN-events in 1-minute windows during the 4 h baseline period and during the 25 minute transient umbilical cord occlusion (indicated by vertical black lines). The events assessed are episodic T/QRS rise (blue), baseline T/QRS rise (green) and biphasic ST events (red). The numbers refer to individual subject numbers.

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  Fig 4. STAN-event warning during fetal hypoxia. First warning for hypoxic distress by the different STAN device events during the 25 minute umbilical cord occlusion. Time t = 0 refers to the start of the umbilical cord occlusion. In two subjects not any STAN-event was detected.

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  Fig 5. Example of failure of the STAN monitor to detect any ST-event during umbilical cord occlusion in subject 3. The top three panels show the calculated heart rate (HR), SDNN (estimate of HR variability) and T/QRS ratio from the fetal ECG as determined using our analysis technique as described [19]. The bottom two panels show STAN events and signal loss. The vertical lines indicate start and end of the umbilical cord occlusion. Note that during cord occlusion the STAN monitor indicated ST signal loss and no events were detected, despite calculated HR, SDNN and T/QRS ratio from the input ECG.