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[The FHR variability of "Shiba goats" in acute hypoxic state]
Fetal heart rate variability in an experimentally induced acute hypoxic state was investigated using chronically prepared fetal goats. FHR variability was calculated using a microcomputer with the R-R intervals of the direct fetal ECG signal measured with a peak detector. The accuracy of the peak detector was 0.1 msec. The formula for FHR variability was as follows: (Formula: see text) A fetal acute hypoxic state was induced by maternal inhalation of a gas mixture low in O2 concentration. The fetal condition was evaluated by blood gas analysis of the fetal carotid artery. In mild fetal hypoxemia due to the maternal inhalation of a gas mixture including 8-10% of O2, both STV and LTV were increased at 10-20 minutes after the beginning of the experiment. Subsequently, both were decreased at 30-40 minutes, but maintained a level higher than that of the control. When severe fetal hypoxemia was induced by the maternal inhalation of the gas mixture containing 4-6% of O2, both STV and LTV increased at 10-20 minutes after induction, then decreased to a level lower than that of the control at 30-40 minutes. No significant difference in fetal PO2 was observed between the 10-20 min. period and the 30-40 min. period of the severe hypoxemic state. But significant differences in pH and BE values were found when the 10-20 min. period and the 30-40 min. period were compared. When data showing the fetal arterial pH and BE to be significantly lower than those of the control at 30-40 min. of the severe hypoxemic state were excluded, significant negative correlations were found between PO2 and STV and between PO2 and LTV . It appeared that FHR variability, both STV and LTV , would increase during the acute hypoxemic state and that they would decrease to a level lower than that of the control after metabolic acidosis occurred due to continuing hypoxemia.
Fetal heart rate variability in an experimentally induced acute hypoxic state was investigated using chronically prepared fetal goats. FHR variability was calculated using a microcomputer with the R-R intervals of the direct fetal ECG signal measured with a peak detector. The accuracy of the peak detector was 0.1 msec. The formula for FHR variability was as follows: (Formula: see text) A fetal acute hypoxic state was induced by maternal inhalation of a gas mixture low in O2 concentration. The fetal condition was evaluated by blood gas analysis of the fetal carotid artery. In mild fetal hypoxemia due to the maternal inhalation of a gas mixture including 8-10% of O2, both STV and LTV were increased at 10-20 minutes after the beginning of the experiment. Subsequently, both were decreased at 30-40 minutes, but maintained a level higher than that of the control. When severe fetal hypoxemia was induced by the maternal inhalation of the gas mixture containing 4-6% of O2, both STV and LTV increased at 10-20 minutes after induction, then decreased to a level lower than that of the control at 30-40 minutes. No significant difference in fetal PO2 was observed between the 10-20 min. period and the 30-40 min. period of the severe hypoxemic state. But significant differences in pH and BE values were found when the 10-20 min. period and the 30-40 min. period were compared. When data showing the fetal arterial pH and BE to be significantly lower than those of the control at 30-40 min. of the severe hypoxemic state were excluded, significant negative correlations were found between PO2 and STV and between PO2 and LTV . It appeared that FHR variability, both STV and LTV , would increase during the acute hypoxemic state and that they would decrease to a level lower than that of the control after metabolic acidosis occurred due to continuing hypoxemia.