[Fetal pulse oximetry. Intrapartum foetal hypoxia evaluation. Comparative study with invasive techniques concerning foetal welfare]

Abstract

Pulse oximetry is a technique that continuously measures the blood oxygen saturation (%SpO2); it has become a standard monitoring method in Anaesthesia, Intensive Care, Neonatology, etc; and it can be helpful in Obstetrics during delivery to monitor foetal welfare. Its advantages are that it is minimally invasive and easy to use. Moreover, SpO2 is a good parameter for measuring oxygen carriage. A saturation below 30% during a time period over 10 minutes is correlated with an acid-base equilibrium (ABE) of foetal scalp blood sample below 7.20, and it is predictive of worse perinatal outcomes. The objectives are: 1. The combined use of both techniques (foetal pulse oximetry and ABE), provides equivalent perinatal outcomes but decreases the Caesarean Intrapartum Rate due to suspicion of a loss of foetal welfare. 2. A correlation was found between foetal pulse oximetry and acid-base equilibrium data such as pH, pO2 and EB.

Subjects and methods: Data was gathered on two groups of eighty patients. In the first group we carried out a follow up of delivery under serialized pH-metry, and in the other group, control of the foetuses was carried out in a combined form with pHmetry and pulse oximetry.

Results: Statistically significant results were obtained concerning delivery in the comparative study of both groups. Following the perinatal results obtained, the data indicates that there are no significant differences between the two groups in the pH values of the umbilical artery or in the Apgar values at one and five minutes after delivery, for which reason both protocols are equally satisfactory. The correlation of the data obtained by pH-metry with those of pulse oximetry was statistically significant.

Conclusions: The combined use of both techniques increases the sensitivity and specificity of the diagnosis of suspected loss of foetal intrapartum wellness, without worsening perinatal outcomes, decreasing the Caesarean Intrapartum Rate due to pathological or non-reassuring foetal electronic monitoring. There is a significant statistical correlation between the results from the foetal pulse oximeter and the values obtained from the foetal scalp blood sample and from the umbilical cord at birth.