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Oxygen test during pregnancy and childbirth
Last reviewed: 19.10.2021
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Methodology. Within 10 minutes, the fetal heart rate is counted or recorded during pauses and during the bout with an interval of 2 minutes. Further for 15 minutes, a continuous inhalation of 100 % oxygen concentration is carried out using a sealed mask. After 15 minutes, the oxygen supply is stopped and the number of fetal heartbeats is again counted, but at an interval of 1 min to catch changes in the fetal heart rate if it suffers from hypoxia. In those cases, when the fetus experiences hypoxia of varying degrees, the cessation of oxygen supply leads, most often in the 4-6th minute, to changes in the heart rate. It is important to note that, according to modern ideas, when giving oxygen, endogenous antioxidants are the primary means of oxygen detoxification in various animal and human species and a means of preventing damage to cells caused by hyperoxia, especially during prolonged exposure.
In the analysis, the curves of cardiotocograms obtained in the oxygen test revealed 3 main types. The curves of the first two types indicate the most favorable prognosis for the fetus (tachycardia of the fetus) and the most unfavorable type 3 of the curve - bradycardia in the fetus - 100 beats / min or less.
Thus, the oxygen test allows you to judge the compensatory capabilities of the fetus and thus avoid unnecessary surgical intervention, or in time to proceed to therapy or surgery, depending on the degree of hypoxia of the fetus and the conditions necessary for rapid delivery.
Determination of interstitial PO 2 from the skin of the fetal head. It has been established that the use of polarographic determination of PO 2 in tissues is a very valuable additional method for determining the evaluation of fetal status during childbirth, since in this case, intrauterine hypoxia can be diagnosed more accurately at earlier stages and more accurately than using cardiac monitoring. A number of authors have revealed a high correlation between PO 2 in the tissues of the fetal head, RO 2 in the umbilical cord blood and the pH of the head tissues. A high correlation between PO 2 and the nature of labor was also revealed , in particular the duration and intensity of contraction and the intervals between uterine contractions. Coordinated generic activity is of great importance for fetal oxygenation, especially the duration of the intervals between uterine contractions, since relaxation of the myometrium during pauses between contractions ensures normal perfusion of blood in the intervillum space and transport of oxygen to the fetus.
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